####018005554#### FXUS64 KHUN 040539 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1239 AM CDT Sat May 4 2024 ...New AVIATION... .NEAR TERM... (Rest of tonight) Issued at 943 PM CDT Fri May 3 2024 Showers and thunderstorms that impacted much of the Tennessee Valley in the later afternoon and this evening, for the most part have ended. However, a few areas of showers remained. The last of showers that were over the Cullman/Marshall county area were slowly weakening as they moved across DeKalb county. A weak disturbance that moved northward across NW Alabama has in part helped new convection form along the AL/TN border. Other light showers over parts of the area were on a fading trend. With less showers and new model output indicating little to no additional showers, have trimmed down rain chances areawide. With numerous boundaries lurking from previous activity, along with a still conditionally unstable environment, development cannot be totally ruled out. Another mild night is expected as low temperatures cool into the low/mid 60s. One worry is a potential for the development of fog in the late night. Much of the area has received measurable rainfall in the last day. If denser high clouds move east of the area, less clouds and a light wind could allow fog to form. But with on-going rain chances and and low/mid altitude moisture remaining, have not bought the fog solution; but it is something not to totally rule out. && .SHORT TERM... (Saturday through Monday) Issued at 202 PM CDT Fri May 3 2024 Saturday, and the remainder of the short term, offers the same forecast challenges. A weak syntopic pattern remains in place with broad mid level ridging to our east allowing for subsequent shortwaves to ripple through the area. The passage of a shortwave tomorrow afternoon will again trigger our highest chances and highest coverage of rain and storms. Once again, tricky pop up convection remains a possibility starting in the late morning ahead of the shortwave. This pattern continues on Sunday into Monday as a mid level trough in the Plains pushes at least two more shortwaves through the area. This will maintain medium to high PoPs across the CWA with highest coverage of rain and storms reserved for each afternoon. While each day will pose a threat for frequent lightning and heavy rainfall, no severe weather is anticipated through the duration of the short term. As for anticipated rainfall, overall weekend QPF amounts will likely vary greatly in spatial coverage. With favorable environmental factors in place for efficient rainfall production, showers could easily dump a quarter to a half inch in a brief period of time for isolated areas. While this alone is not enough to raise flooding concerns, periods of heavy rainfall could continue to trigger ponding of water and nuisance flooding for urban area. When it's not raining, the tropical airmass will make for a very humid weekend. Highs remain in the low 80s with dewpoints in the high 60s each day. && .LONG TERM... (Monday through Thursday) Issued at 433 AM CDT Fri May 3 2024 After warm frontal convection spreads northeastward and out of the region late Monday morning, the TN Valley will be solidly within a very warm/moist tropical airmass, with dewpoints expected to rise into the m-u 60s as southwesterly low-level flow strengthens. Although this will contribute to greater instability (especially during the afternoon hours), a mid-level ridge will shift across the region downstream from the central Rockies upper low as it begins to spread northeastward into the northern Plains, and this should yield a lower coverage of mainly afternoon thunderstorms from Monday-Wednesday. Overnight lows will steadily increase into the u60s-l70s through the middle of next week (due to both elevated SW winds and moisture advection), with highs also warming into the mid (to perhaps upper) 80s by Wednesday. Although details are unclear at this time range, conditions will become more favorable for convection at the end of the extended period (Wednesday night/Thursday), perhaps in the form of MCS activity that may initiate along a cold front to our northwest and propagate southeastward into the local area. Should this scenario materialize, conditions will be favorable for organized severe thunderstorms across our region, with boundary layer dewpoints in the u60s-l70s beneath a belt of mid-level WSW flow of 35-45 knots. && .AVIATION... (06Z TAFS) Issued at 1239 AM CDT Sat May 4 2024 Scattered to numerous showers and thunderstorms continue across the area, with a general motion to the NE around 15kt. Additional development is possible over the next few hours, as well. Outside of convection, VFR conditions are expected. Before daybreak Sat, there is a risk of patchy fog forming in/near areas that recently received heavy rainfall. Otherwise daytime heating and resultant instability could allow more showers and storms to form Sat afternoon. Given uncertainty on development and where the activity will impact, have a VCTS for the latter portion of the TAF at both terminals. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...RSB SHORT TERM...RAD LONG TERM...70/DD AVIATION...RSB ####018007086#### FXUS65 KBOU 040539 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1139 PM MDT Fri May 3 2024 .KEY MESSAGES... - A few showers and storms across the eastern plains this afternoon into tonight. - Warmer and windy on Sunday. - Active, cooler, and mainly windy pattern from late Sunday through most of next week. A few chances of accumulating snow across the mountains with isolated/scattered showers across the plains. && .UPDATE... Issued at 848 PM MDT Fri May 3 2024 We observed one severe thunderstorm in eastern Lincoln County this afternoon which generated strong outflow winds measuring at least 62 mph in and near Hugo. All of that action has now pushed east, with just some lingering light showers over the mountains where there's sufficient orographic lift to tap into a stream of mid- level moisture. These should dwindle in the next few hours as this corridor pushes east. Cloud cover appears less expansive than initially indicated, so have made pertinent adjustments and also lowered minimum temperatures for tonight by a couple degrees for most areas. Breezy conditions remain in the plains following the front, particularly in Lincoln County, but winds will gradually subside as the lower levels decouple. && .SHORT TERM /Through Saturday/... Issued at 303 PM MDT Fri May 3 2024 Current analysis shows a lee cyclone across the Palmer Divide area. From the north, a cold front is advancing southward with a push of gusty northerly winds behind it. Gusts 35-45 mph are being reported across the region from the front. Along this front, a line of thunderstorms moves across the northeastern plains. SPC mesoanalysis shows an axis of marginal instability across the far east plains (< 500 J/kg SBCAPE). This is overall supported by an shortwave trough moving eastward just north of the Colorado border. For the remainder of the afternoon and into the evening expect showers in the mountains with another round of showers moving across the northern border onto the plains. Areas such as Lincoln County remain unstable ahead of the advancing front, so can't rule out any shower or storm development in those areas in the next hour. Showers linger across the mountains this evening with remaining showers/storms exiting the eastern plains. Behind the front, temperatures cool sufficiently overnight with lows in the low to mid 30s across the plains. We are approaching Frost/Freeze headline territory for areas on the plains; however, given its current rating of mixed susceptibility for vegetation and closeness to average last freeze, we decided to hold off on headlines. For tomorrow, expect cooler temperatures with highs in the 60s across the plains, 50s for foothills/mountain valleys, and 40s for the mountains. Expect another round of showers and a few storms in the afternoon (marginal CAPE), mainly over the higher elevations and south of I-70. && .LONG TERM /Saturday night through Friday/... Issued at 303 PM MDT Fri May 3 2024 A strong upper low will be located near northern California on Sunday morning, with increasing south-southwesterly flow over our forecast area through the day. The result will be a warm, dry, and breezy end to the weekend as the dryline shifts towards the CO/KS/NE border. Temperatures should warm into the mid to upper 70s. Model soundings suggest boundary-layer average winds of 30-45kt, which would lead to wind gusts of 45-55 mph. Some guidance keeps just enough moisture out in the far eastern plains for an isolated shower or storm, though the models that keep some moisture here also maintain a strong cap through the day. The closed upper low is expected to transition to a sharp, negatively tilted trough axis by Monday morning... which then ejects into the northern Great Plains from Monday into Tuesday. A quick round of mountain snow is likely with the passage of the trough axis, though cross-sections show somewhat sparse moisture on this side of the trough. For the plains, a few showers will be possible, but the main story will be wind. A bora-like event appears likely as a colder westerly flow develops. Temperatures will hover in the upper 50s/low 60s. Gusty winds will continue, especially across the high country. Zonal flow is expected to persist Tuesday into Wednesday as the upper trough stalls over the far northern Great Plains. Guidance shows a bit of moisture lingering in this flow, which would lead to scattered snow showers across the high country while the plains remain generally dry. With fairly strong mid-level flow, gusty winds will be slow to subside in this period. As we get into the latter half of next week, there is increasing uncertainty in the overall synoptic pattern. Recent guidance attempts to stall out the trough or even retrograde it back to the south and west. Unsurprisingly, ensemble guidance lacks a clear, definitive signal, with a substantial amount of spread for T/QPF as we get into Thursday/Friday of next week. We'll likely have a ways to go until we see better agreement in this timeframe... but at the very least, it does appear that a cool and unsettled pattern will continue. && .AVIATION /06Z TAFS through 06Z Sunday/... Issued at 1134 PM MDT Fri May 3 2024 VFR conditions are expected through the TAF period. Southeast winds should continue through Saturday afternoon. Scattered showers will occur west of all terminals along the higher terrain, but it is possible a shower or two could spread into KBJC by Saturday evening. Models have favored this outcome thus including a VCSH between 00-02Z. There is lower confidence in this outcome for KAPA and KDEN due to unfavorable conditions for thunderstorm development thus kept it out of the TAF for now. Additionally, winds increase this afternoon gusting between 20-27kts briefly from 21-22Z until 00Z. Drainage winds are unlikely by Saturday night and should remain south. && .FIRE WEATHER... Issued at 303 PM MDT Fri May 3 2024 Increasing fire danger is expected late this weekend into early next week behind the strong storm system. Gusty winds should develop on Sunday and continue daily through at least mid-week, with a gradual drying trend from Sunday through Tuesday. Near- critical to critical fire weather conditions appear likely across portions of the lower elevations at times, especially south of I-70. However, recent rainfall and ongoing green-up across the plains may limit overall fire danger. Still a couple of days out at this point, so no watches have been issued... but we'll be watching closely as we get into the weekend. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Rodriguez SHORT TERM...Mensch LONG TERM...Hiris AVIATION...AD FIRE WEATHER...Hiris ####018006927#### FXUS62 KMHX 040541 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 141 AM EDT Sat May 4 2024 .SYNOPSIS... High pressure will continue offshore today and into the weekend. A slow moving cold front will linger over the area Saturday before retreating northward on Sunday. Thereafter weak troughing across the Eastern Seaboard and warm moist southerly flow will lead to unsettled conditions through early next week. Drier conditions are expected by mid week, but will lead to increasing heat and humidity as ridging builds. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 10 PM Friday... Stalled front remains draped over our northern tier as of this update bringing plenty of low stratus and even some fog across the NOBX and portions of mainland Dare as of this update. As a matter of fact we currently have ongoing marine dense fog advisories going through 11PM and an SPS for fog in the NOBX including Manteo through 12AM for the threat for patchy areas of fog with visibilities of less than 1/2 mile at times. Will reevaluate later this evening to see if these need to be extended. Do think fog should lift in the next few hours, but stratus should remain through the rest of tonight. Current expectation is for stalled front to remain in place but for patchy fog and low stratus to continue to march SW'wards this evening eventually encompassing the entire forecast area as low level moisture continues to increase and a low level inversion sets up. We remain dry overall as lows get into the low to mid 60s. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TODAY/... As of 300 PM Friday...Saturday will start off cloudy, low cloud cover slowly rising with the help of daytime heating. Weak cold front will remain over ENC with east/southeasterly flow expected most of the day. Stable onshore flow will limit instability development, and with drier air holding on across the area for most of the day, it is looking to be a mostly dry day with the exception of the coastal plain where some isolated shower/thunderstorm development may occur. Temperatures will remain above normal but a bit cooler than Friday with highs ranging from the upper 70s to low 80s (cooler along the coast with the onshore flow). && .LONG TERM /TONIGHT THROUGH FRIDAY/... As 315 AM Fri...A weak cold front will dip southward into the Carolinas this weekend with some scattered showers and thunderstorms possible. Unsettled weather will continue for the first half of next week as weak troughing lingers over the East Coast and warm moist southerly flow develops. By mid next week drier conditions will return but will be accompanied by an increase in heat and humidity. Sunday...Winds will veer to the south Sunday as the front retreats to the north. However this will bring better moisture/instability to the area and allow for scattered showers and thunderstorms to develop Sunday afternoon with the most widespread rain across the coastal plain. Similar temps expected with highs in the 70s to low 80s. Monday and Tuesday...High pressure will rebuild well offshore early next week while weak troughing remains along the Eastern Seaboard. With a moist and unstable airmass in place, diurnally enhanced showers and thunderstorms will develop with the best chances again over the coastal plain. Highs will reach the upper 70s to low 80s again Monday with increasing low level thicknesses boosting Tuesday's highs into the low to mid 80s. Wednesday and Thursday...Drier conditions are expected mid week as upper level riding builds back over the Southeast. However, increasing low level thicknesses and continued southerly flow will lead to hot and humid conditions will afternoon highs reaching the upper 80s to low 90s inland, and the low to mid 80s closer to the coast. Some isolated airmass showers and thunderstorms are also possible each afternoon. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... SHORT TERM /through Saturday/... As of 0115 Saturday...SubVFR flight cats overnight with fog/stratus in place. At best, IFR expected inland with coastal sites experiencing VLIFR VIS and CIGs. Fog is expected to dissipate by 13Z, but subVFR CIGs will linger into at least the late morning with IFR CIGs lifting from W to E between 13-16Z and MVFR ceilings then lifting to VFR conditions by Sat afternoon. Could see an iso shower or tstm especially across ISO/PGV Sat afternoon as well but confidence is too low to include this in the TAFs. LONG TERM /Saturday through Wednesday/... As of 315 AM Fri...Generally VFR conditions are expected through early next week, however increasingly unsettled conditions could lead to moments of sub- VFR conditions each afternoon/evening. && .MARINE... SHORT TERM /through Saturday/... As of 1010 PM Friday... Only update since the previous one was to include a marine dense fog advisory for portions of the NOBX coastal waters and the Croatan and Roanoke Sounds as latest webcam imagery and obs have shown continued visibilities of 1 NM or less here. Will reevaluate within the next hour or so but this marine dense fog advisory may need to be extended further depending on what obs look like. Prev Disc...MWS has been issued for Albemarle/Croatan/Roanoke sounds and the Alligator River, along with coastal waters from Duck to Oregon Inlet this evening for a quick wind shift from westerly to easterly and gusty conditions behind a back door cold front. Potential exists for infrequent gusts of 30kts between 5-8pm today for the Albemarle sound, as easterly flow results in funneling. As we get into tonight gusts will lessen to 10-15kts behind the front. Winds will remain east/southeasterly tomorrow, sustained 10 kts gusting to 15 kts. Seas are calm today, starting to build from the north overnight into Saturday. By Saturday evening, waves will be 2-4ft for coastal waters, highest north and east of Hatteras. Fog threat persists into the weekend for coastal waters, sounds, and rivers once again. LONG TERM /Saturday night through Wednesday/... As of 315 AM Fri...Decent boating conditions are expected this weekend with slightly worsening conditions developing early next week. Winds will come around to the south of Sunday at 5-15 kts. SW winds then develop Monday through most of next week with winds increasing to 10-20 kts. Seas will be generally 2-4 ft through Monday and then increase to 3-5 ft Tuesday. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...None. MARINE...None. && $$ SYNOPSIS...MHX NEAR TERM...RCF SHORT TERM...RJ LONG TERM...SGK AVIATION...SGK/CEB MARINE...SGK/RJ ####018010464#### FXUS63 KLBF 040542 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 1242 AM CDT Sat May 4 2024 .KEY MESSAGES... - Strong to severe thunderstorm development is expected Friday afternoon and evening with damaging wind gusts and locally heavy rainfall the main concerns. - Another episode of severe weather appear increasingly likely for Monday, but confidence in impacts in the local area is low at this time. - Cooler temperatures are likely for Day 5 (Tuesday) and beyond. && .SHORT TERM /THROUGH TONIGHT/... Issued at 243 PM CDT Fri May 3 2024 Immediate concern focuses on the threat for severe thunderstorms this afternoon and evening across much of western Nebraska. As of 19z, convection was developing along a stationary boundary draped from the southern Panhandle into north central Nebraska or roughly just north of a SNY to just south of a VTN line. Ahead of this feature, strong southerly flow was driving low-level convergence in immediate proximity to the boundary. Moisture in the warm sector is marginal at best with dew points reading the upper 30s to low 40s as air temperatures read the upper 60s to lower 70s south of Highway 2. This will greatly limit instability with MLCAPE values only progged to approach 1000 j/kg for areas south of Highway 23. Further north, values will likely remain 750 j/kg or less with rapid decrease with northward extent. Even so, forcing should be fairly strong with the frontal boundary progressing through the area. At the same time, flow aloft remains fairly strong with h5 flow exceeding 40 knots. With southerly surface flow, this is producing moderate 0-6km BWD values of 40 to 50 knots. Forecast soundings show inverted-v profiles ahead of the main line of convection but with a lack of drier air aloft, max theta-e values are marginal only falling to around minus 10 degC. At the same time, DCAPE values are on the lower end as well with most locations reporting values of less than 750 j/kg. That said, flow off the surface immediately following the frontal boundary will respond accordingly as a strengthening cold pool drives this south quickly this evening. These elevated winds will likely be efficiently mixed to the surface by the convection. This will support at least a concern for isolated damaging wind gusts in the local area. While hail cannot be ruled out, believe this threat is fairly low given lack of greater instability aloft. As forcing translates east along the boundary, increasing moist advection will help increase coverage of thunderstorms on approach to southwest and eventually central Nebraska later this evening. Coverage should blossom as a result with a growing concern of locally heavy rain. While PWATs remain low, less than 0.75", rain rates exceeding 0.50"/hour with potential for training storms should lead to a smaller area of QPF likely exceeding 1.00" from southeastern Lincoln/Frontier Counties up through central Nebraska to include southern Custer County. These areas have recently seen fairly heavy rainfall events as departures from normal values exceed 150% and even approaching 300% for some of these locations. This has helped drive county based Flash Flood Guidance to around 1.5"/2.0" for the 1 hour/3 hour values respectively. Latest HREF guidance shows Probability Matched Mean values of 3 hour QPF exceeding 1.25" for many of the mentioned areas and even peaking around 2.0". This suggests some hydrology concerns so this will need monitored as the evening progresses. Believe incoming dry air behind the front and the main source of lift should clear the area by Midnight Friday night though lingering stratiform precipitation could last into the early morning hours Saturday. This later departure of clouds and precipitation should help keep overnight lows across our east on the milder side with its implications on any frost threat covered at the start of the long term discussion below. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 243 PM CDT Fri May 3 2024 Saturday and Sunday...Departing trough to the northeast will allow mid-level heights to rise as shortwave ridging builds in its wake. This will promote dry conditions for Saturday as surface high pressure settles through the area. Forecast lows for Saturday morning do not line up with latest guidance on vulnerable vegetation therefore thinking no frost headlines are needed at this time. Supporting this thought is steady northerly winds with potential for lingering low stratus across our eastern zones. Admittedly, the residual cloud cover behind a progressive cool front tends to be overstated in NWP guidance. Even with the more pessimistic guidance though we see steady enough flow in the low-levels to prevent full boundary layer decoupling with surface winds remaining in the 10 to 15 mph range through sunrise. Further west where the setup for radiational cooling will be more favorable, lows will again fall below the freezing mark. That said, the areas remain outside the latest guidance for susceptible vegetation therefore no Frost or Freeze headlines are expected. All that said, lows will range from the upper 20s west to upper 30s east. Daytime highs will climb into the low to middle 60s with light and variable winds generally 15 mph or less through the daytime. Ridge breakdown begins Sunday as the next shortwave trough approaches the central Rockies late in the day. With developing surface low to the west and departing high pressure to the east, a west to east pressure gradient will compress locally and help drive some increasing southerly winds late Saturday into early Sunday. This will promote increasing moisture advection into the area. This will also favor a fairly stubborn low stratus deck across our western zones that may struggle to clear out until later in the day. As a result, cool temperatures will remain stubborn with afternoon highs remaining in the low to middle 60s. Winds will be on the stronger side for areas west of Highway 61 where gusts may climb into the 35 to 45 mph range with 25 to 35 generally expected elsewhere. Can't rule out a few light rain showers west of Highway 83 in the area of greatest moisture advection but given the general lack of convergence and limited WAA, believe this potential is fairly low with minimal if any impacts expected. Monday...A well advertised storm system will traverse the Plains, bringing with it the potential for a fairly robust severe weather episode across the region. Low-level southerly flow will persist early into the day helping increase surface moisture as a dryline tightens from western South Dakota down through western Texas. Aloft, the aforementioned shortwave disturbance will begin to take a negative tilt as it ejects onto the Plains early in the day. A concentrated area of significant height falls in concert with strengthening upper-level divergence will help foster the development of an elongated area of low pressure stretching from southern Colorado up through eastern Montana. Within the plume of richer low-level moisture, the combination of mild afternoon highs and steep mid-level lapse rates will lead to increasing instability within a strongly sheared environment. For now, greatest confidence in severe weather remains east and southeast of the local area where all hazards will be possible. Closer to the local area, expecting the greatest threat to favor large hail and damaging wind gusts. That said, the progressive cold front overtaking the dryline will encounter modest instability in our eastern zones so the prospect for severe weather affecting the local area cannot be ruled out. The latest SPC Day 5 severe weather outlook highlights areas east of Highway 83 in the 15% probability, or the equivalent of a Slight Risk (level 2 of 5). For now, have no qualms with this but impacts from morning rain and thunderstorms within the strong WAA within the warm sector and how this affects the afternoon environment will need to be closely monitored. Behind the boundary within the drier airmass invading the area, strong CAA will support windy conditions with gusts nearing the 35 to 45 mph range out of the west. Temperatures will likely falter as a result but this looks to be late enough in the day that afternoon highs will still reasonably reach the upper 50s to lower upper 60s across the area. Tuesday and beyond...mid-level heights will be quick to fill in early Tuesday as a cutoff low at h5 takes shape across the northern High Plains. This feature will likely remain fairly stagnant through the middle of the upcoming week with a slight cooling trend in temperatures expected for the later half of the forecast period. Latest ECMWF Extreme Forecast Index (EFI) guidance hints at a continuation of strong winds from Monday into Tuesday. Another cool front will traverse the area by late Tuesday into Wednesday, bringing about a more notable drop in temperatures. Some low- end PoPs will also dot the forecast, favoring areas north of Interstate 80. For now, confidence is greatest in precipitation Thursday afternoon and evening. Higher percentile values from the NBM suggest the potential for wetting rains but variances in deterministic and other ensemble guidance limits confidence in this occurring thus far. Temperatures will favor below normal values through the time frame which will include overnight lows falling to near the freezing mark. This would line up with frost/freeze climatological median dates so potential need for headlines next week cannot be ruled out. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1239 AM CDT Sat May 4 2024 MVFR and IFR ceilings will clear from the west early this morning. All areas across western and north central Nebraska should be VFR by sunrise. Skies will remain clear through Saturday with light winds. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...NMJ LONG TERM...NMJ AVIATION...Taylor ####018005633#### FXUS65 KTFX 040543 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1143 PM MDT Fri May 3 2024 ...AVIATION SECTION UPDATED... .SYNOPSIS... Lingering showers and snow showers will be around through the early evening ahead of a mild and dry Saturday. Precipitation chances will return Sunday into much of next week, with potential for an impactful spring system over the middle of next week. && .UPDATE... Surface high pressure is dominant across the state this evening. Rain showers have dwindled down as skies continue to clear. No major changes were made to the update as dry weather stays overnight. Patchy fog will be limited due to drier air at the surface. -Wilson && .AVIATION... 1143 PM MDT Fri May 3 2024 (04/06Z TAF Period) Lingering clouds from isolated shower activity earlier this evening are quickly giving away to mostly clear skies. Aside from some isolated fog patches later tonight/early Saturday over the far southwest valleys and portions of the plains, VFR conditions associated with high pressure over the Northern Rockies are expected for most if not all of the 04/06Z to 05/06Z TAF period. However, keep in mid that higher clouds do increase later tonight into Saturday, and a few light showers may lift northward into far Southwest Montana around 04/00Z and beyond. Light east to southeasterly surface winds increase on Saturday and may gust up to 25 mph at times. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 255 PM MDT Fri May 3 2024/ Through Saturday...Transient shortwave ridging is beginning to build in across the Northern Rockies between one upper disturbance exiting eastward across Southern Canada and another approaching the Pacific NW. Lingering northwesterly flow aloft will combine with daytime heating to result in rain and snow showers the remainder of this afternoon and early evening, primarily across the plains. Clearing skies and light winds tonight will allow for patchy fog formation into Saturday morning, but is not expected to pose many impacts at this time. Saturday looks to be a pleasant day as the aforementioned ridge moves overhead, with the only potential blemish being breezy easterly to southeasterly winds across the plains in the afternoon. Daytime highs look to rise to near to a touch above average in most areas. -AM Saturday night into next week...Deep southerly flow aloft develops over Southwest MT Saturday night ahead of a closed low moving onto the Pacific NW coast. This system will trek eastward into S ID on Sunday, placing the Northern Rockies on the ascent side of the system for northward expansion of shower and isolated thunderstorm activity, though temperatures will remain near average for one more day. H700 flow slows down by Sunday afternoon and MU CAPE looks to be around 100 to 300 J/kg (highest southwest MT), so not expecting anything beyond general thunderstorm risks at this time. Ensembles remain in decent agreement with the aforementioned closed low swinging NE into E MT and slowing down some Monday through early Thursday. Although, there are differences on the precise path of the low, most favor cool, wet, and windy periods during this timeframe. According to the NAEFS Standardized Anomaly, H700 temperatures are forecast to be around -8C for much of this event, which would support mountain accumulating snow, but mostly rain at lower elevations. Current probabilistic forecasts for rainfall highlight the eastern portions of North-central MT with the highest chances (50 to 70%) for 1 inch of rainfall during the 72 hr period ending next Thursday at 6 am, with nearly all locations in the CWA standing at least a 50% for a quarter inch of rainfall for the same time period. The one drier exception looks to be southwestern valleys from Dillon to the Three Forks area. As mentioned earlier, thermodynamic profiles should confine accumulating snow to mountain areas, with the Little Belts and the Madison/Gallatin ranges seeing 60% + chances for 8 inches of snow or more Monday through Thursday, with most of it falling Tuesday night into Wednesday. H700 flow on the backside of this low will be at or above the 30 to 40 kt range for an extended period, resulting in gusty to at times strong northwesterly surface winds. While all days Monday through Wednesday look to be on the windier side, Tuesday is being singled out by the EC Extreme Forecast Index and NBM probabilistic forecasts as the windiest day overall, with many locations seeing 70% + chances for wind gusts above 40 mph. Drier and milder conditions move in for Thursday and Friday of next week, though around 50% of the ensembles support weaker troughing remaining in place for non-zero chances for precipitation and near average temperatures heading into next weekend. - RCG && .PRELIMINARY POINT TEMPS/POPS... GTF 29 64 42 63 / 0 0 10 40 CTB 28 60 37 59 / 0 0 10 30 HLN 32 69 44 69 / 0 0 10 60 BZN 27 67 42 65 / 0 0 10 70 WYS 21 60 36 52 / 0 0 30 90 DLN 30 66 43 60 / 0 10 40 70 HVR 27 64 39 71 / 0 0 0 20 LWT 25 59 36 65 / 10 0 10 30 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls ####018012046#### FXUS65 KPUB 040543 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 1143 PM MDT Fri May 3 2024 .KEY MESSAGES... - Severe thunderstorms will be possible later this afternoon and through the evening over the eastern plains. Wind gusts in excess of 60 mph, hail of up to 2 inches in diameter possible. A brief landspout or weak tornado cannot be ruled out. - A cold front will move through later this evening over the plains, with colder temperatures and gusty winds out of the northeast behind it. - General thunderstorms are possible elsewhere over the plains and over the eastern mountains, which will continue throughout the night for some areas, mainly over the far southeastern plains and Raton Mesa area. - Frost conditions will be possible tonight over El Paso County. - Increasing winds and fire danger early next week with a trend towards cooler and wetter conditions for late week. && .UPDATE... Issued at 815 PM MDT Fri May 3 2024 Have allowed the Red Flag Warning to expire this past hour, as winds continue to diminish and RH values improve. Have kept the Severe Thunderstorm Watch in effect this evening, as additional strong to severe storms remain possible. Southward moving strong cold front will encounter stronger south southeast winds along with dewpoint air still in the 40s to low 50s. This should allow at least isolated thunderstorm development, some of which will still be capable of producing hail to the size of quarters and wind gusts to 60 mph. Highest chances for this to occur late this evening, is along and southeast of a Kim to Lamar line. Any remaining development should be southeast of the CWA by around the midnight time frame. && .SHORT TERM /THROUGH SATURDAY/... Issued at 224 PM MDT Fri May 3 2024 Currently and through tonight... A major shortwave trough is continuing to approach the region, with the development of a lee-side low by later in the afternoon as the trough axis moves overhead. As this pushes out over the plains a slightly deepens, it will force a cold frontal boundary to move down from the north over the plains. A dryline is going to establish itself, where there are currently 50+ dewpoints over northeastern New Mexico that will make their way up over far southeastern Colorado later this afternoon, this will act as a triggering mechanism for pre-frontal convective development once the cap completely erodes and the convective temp is achieved, which may turn severe given the higher dewpoints and thus increased low-level instability. An increasing low-level jet out out of the southwest will also increase shear necessary for further updraft enhancement and may allow for severe thunderstorm development for the next couple of hours, mainly over Las Animas County and east. A consensus of the latest high res guidance has the front beginning to move over northern El Paso County by as early as 7 to 8 PM, and then push through the CWA by around midnight. The timing of the front could be sooner, depending on whether or not if it is accelerated by outflow from convection that develops along and behind the boundary. Currently, there have already been multiple cells that have initiated over this area, which will likely continue to develop as the lower levels further destabilize by early evening as the low- level jet increases with effective shear of a magnitude around 30 kts or greater. MLCAPE is also going to increase to 1000 J/kg or greater, especially over Prowers and Baca counties, mainly after 4pm. With this, the potential for thunderstorms becoming severe will increase going into the later afternoon/early evening hours, especially anywhere from La Junta to Kim, and eastward. There are also going to be general thunderstorms possible over the eastern mountains and along portions of the I-25 corridor, mainly south of Pueblo County, that will continue to move off to the east-northeast after development. Dry conditions, with low relative humidity values and gusty southwesterly winds will continue to keep fire weather conditions going until around 9 PM in the San Luis Valley, although RH values should recover enough to allow the Red Flag Warning to come down by this time. The latest CAM guidance and HREF helicity tracks favor development of stronger, and possibly severe, cells over Prowers and Baca counties between 6 to 8 PM. In addition, the latest HRRR model also puts the development of a cell over Baca, with easterly winds turning into it at 00Z (7 PM), suggesting that there could be increased SRH values right around this time and possible supercell development, with the capabilities of producing a brief landspout and/or weak tornado. It also has something similar right around the same time over Prowers County, as well as the development of a strong cell right on the edge of northeastern Kiowa County. The NAM4km Nest has also been persistent with the past couple of runs of having a pre-frontal cell develop with over the northwestern Baca County/Bent County and then move into Prowers County right around the same time. Colder air advection moving in behind the frontal passage that will occur later this evening will allow for temperatures to continue to drop, especially as skies further clear. This will allow for temperatures over El Paso County to drop to near, or below, the freezing mark. Due to this, there will likely be some areas of frost. Stratus will also develop, mainly along the I-25 corridor from Pueblo County and northward to Monument. There could still be some showers, and possibly a thunderstorm, continuing into the early morning hours of tomorrow. As the lower levels continue to stabilize, showers will also continue to diminish and move southeastward and out of the CWA towards daybreak. Lows will bottom out into the 30s to low 40s over most of the plains, and generally in the upper teens and 20s for high country. Tomorrow... With colder air already in place, it will be more stable over the plains, and notably cooler. Highs will likely remain in the 60s over a majority of the plains and San Luis Valley, and only 40s to 50s for the higher terrain. With residual moisture, and increasing mid- level flow out of the southwest coupled with orographic lifting, there will be showers and thunderstorms developing in the afternoon hours over the higher terrain. This will get pushed out over the plains by later in the day. These should be more of your "garden variety" type thunderstorms, although there could be an isolated storm or two that is on the stronger side. With more of an inverted- v profile, some of these storms may result in some gusty outflow winds to 50 mph or greater, and there could be hail up to 1/2 inch with the stronger storms. The plains will likely remain dry with more stable air in place, although a few of the showers/storms could move out over the adjacent plains and portions of the I-25 corridor. -Stewey && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 224 PM MDT Fri May 3 2024 Weak wave in southwest flow ejects across CO Saturday evening with cool stable upslope flow maintaining across the plains. A few showers may drift off into the adjacent plains but they should diminish as the move off the mountains into the more stable airmass. Have trimmed eastward extent of pops into the I-25 corridor during the evening. Showers and thunderstorms will diminish across the mountains behind this feature in the evening but could regenerate across the far eastern plains late Saturday night as the low level jet increases. Any isolated nocturnal convection will have limited CAPE resulting in some weak elevated showers/thunderstorms into Sunday morning. Temperatures then rebound for Sunday as southerly flow increases across the region ahead of the next upper low moving into the Great Basin. Will need to watch the San Luis Valley for potential Critical Fire Weather conditions until green up occurs. For now, coverage and magnitude looks too limited with RH the most limiting factor for Sunday. Showers and thunderstorms will redevelop across the Continental Divide as moisture increases ahead of the upper low. Out east it remains largely dry. Will need to monitor the position of the dry line but for now dew point return and CAPE looks limited with little to no initiation along the boundary in the afternoon. Upper low lifts out across northern CO Sunday night and Monday. With the more northern storm track, this puts southern CO under the dry and windy region of the storm. Latest NBM shows potential for wind gusts greater than 50 mph in the 70-90+ percentile, especially along and south of highway 50 Monday morning. We could be looking at brief near high wind potential Sunday morning if we can mix 50-60 kts down to the surface Sunday morning as the cold front moves through. In spite of the cool down, it will be very dry and likely a critical fire weather day for the San Luis Valley and southern portions of the southeast plains where fuels are still critical. The Continental Divide will pick up some snow Sunday night through Monday morning with a diminishing trend in the afternoon as the storm ejects to the northeast. The windy and mostly dry pattern continues for Tues and Wednesday with temperatures rebounding. Then we trend towards a cooler and potentially wetter pattern as low pressure stalls out over the western U.S. and a cold front moves through the plains bringing post frontal upslope flow Thurs into next weekend. Thursday could potentially be the coolest and wettest day with snow levels dropping to around 7000 feet across the southeast mountains. Still some details to resolve on the track and strength of the low which will drive the degree of upslope and precipitation amounts. EC is weaker with the upper low and magnitude of upslope, and therefore has less QPF/snow. Probabilities of greater than 3" of snow accumulation is less than 30 across all but the central mountains from the National Blend of Models. Central mountains fair a little better with probabilities for up to 6 inches up to 40%. This will bear watching as details become more certain. -KT && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1134 PM MDT Fri May 3 2024 VFR conditions with mainly dry weather is expected across the TAF sites this forecast period. While conditions remain clear at ALS this morning, low stratus will likely build back towards PUB and COS early this morning. Ceilings are currently VFR and expect them to remain that way as they move across the terminals. If ceilings were to fall to MVFR, think COS would have the higher chance of observing these lower ceilings. Once again, think this is a low chance though. Any lower ceilings clear out by early to mid morning, with clearer skies expected for much of the day. Will see the lighter winds in place this morning increase during the day, with southeast winds at COS and PUB and south southwest winds at ALS. Highest gusts at all sites look to be in the mid 20 kt range. Scattered showers with isolated thunderstorms will develop over the higher terrain this afternoon, and think conditions will remain dry at all sites. With a slightly higher chance for a shower at ALS, have included a VCSH during the afternoon time frame. && .PUB WATCHES/WARNINGS/ADVISORIES... Frost Advisory until 9 AM MDT Saturday for COZ084-085. && $$ UPDATE...RODRIGUEZ SHORT TERM...STEWARD LONG TERM...KT AVIATION...RODRIGUEZ ####018010148#### FXUS61 KAKQ 040544 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 144 AM EDT Sat May 4 2024 .SYNOPSIS... A backdoor cold front pushes south and west of the area tonight. On and off shower chances are expected Saturday and Sunday. Summerlike conditions return to the area for next week with daily chances of showers and storms. && .NEAR TERM /THROUGH TODAY/... As of 910 PM EDT Friday... Key Messages: - On and off showers expected tonight through Saturday with the highest coverage inland. - Becoming dreary for all areas Saturday with extensive low-level cloud cover. Evening wx analysis shows that the backdoor cold front has just about crossed the FA (with a few obs in the s-central VA Piedmont showing mid 70s w/ mid 60s dew points. Scattered showers/tstms have developed near the front across our far SW zones. Meanwhile, a decent E-NE wind continues elsewhere (especially near the coast where there are areas of drizzle/fog...although VSBYs are mostly at or above 1SM attm). The front will settle to our SW overnight, but some elevated instability (based around 800-900mb) will overspread at least the western half of the FA overnight. Expect showers and potentially a tstm or two along/west of I-95 overnight, with no precipitation outside of drizzle near the coast. Patchy fog may also move onshore across SE VA and NE NC, but continue to think visibilities will not get too low given the elevated winds. Overnight lows will be chillier than the previous few nights with upper 40s on the MD Eastern Shore and 50s for most of the rest of the area (lower 60s down along the Albemarle Sound). The front will be well W/SW of the area by tonight into Saturday. Sfc high pressure will be left in its wake across New England. This will wedge a cool/moist low-level airmass over the entire area for the day Saturday. This will also keep cloudy conditions in place. The best forcing/lift and moisture remains across the W, so expecting the highest coverage Saturday mainly W of I-95. Despite this, it will tend to remain unpleasant even towards the coast w/ onshore flow and patchy drizzle. Continue to trend highs lower with temps struggling to reach 60 across the N, with mid 60s-low 70s elsewhere. There is a chance that far SW portions of the CWA (e.g., Northampton/Bertie Counties in NC) reach the upper 70s, but this may even be overdone. These values are still below NBM (especially S). On and off "showery" rainfall continues overnight Saturday with lows in the 50s N to 60s S. QPF through tomorrow averages from up to 0.50" across the W, 0.1-0.4" central, and 0.00" to a few hundredths of an inch closer to the coast. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... As of 330 PM EDT Friday... Key Messages: - Continued unsettled, but warmer, Sunday. - More humid on Monday with showers and storms areawide. The front is expected to lift back N Sunday into Monday, shifting the low-level flow to the S. These factors should act to scour out the dreary conditions seen on Saturday. However, still expecting shower redevelopment in the aftn hours as temps warm into the 70s and 80s and the residual front and a weak disturbance aloft remains near the area. An early look at some CAMs show that they are not particularly enthusiastic at widespread rainfall coverage, which makes sense given a lack of any focused areas of lift. Lows Sun night in the 60s. Upper heights begin building back N for Monday with high temps warming into the low 80s areawide. Despite the warmer temps, a lee trough is expected to develop in the aftn and evening hours. Combined w/ an approaching shortwave from the OH River Valley, showers and storms are expected to develop over the higher terrain in the afternoon and slide eastward into the evening. Models show around 1000 J/kg of CAPE developing with rather weak shear. Therefore, the severe threat looks relatively low, but cannot rule out a stronger storm or two. Soundings do show a rather saturated atmospheric column (PWATS potentially reach or exceed 1.5"), which could lead to some heavier downpours. Dew points also increase into the mid-upper 60s so the humidity will make it feel more like early summer. Shower/storm activity diminishes inland after midnight, but may linger closer to the coast overnight. Lows remain mild in the mid 60s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 335 PM EDT Friday... Key Messages... - A more summer-like pattern with warmer days and chances for late afternoon and evening showers and storms appears to be on the way for the middle to end of next week. We get into an almost summertime pattern by Tuesday as the ridge aloft builds overhead with afternoon/evening showers and thunderstorms each day being triggered by the lee side trough. The GFS and ECMWF both suggest the ridge breaks down slightly by Wed/Thu with stronger 500mb flow of up to 50 kt by Wed afternoon. Along with this, those models suggest weak shortwaves (likely of mesoscale origin from convection over the Ohio Valley and central plains) moving through the area. These convective complexes may also move through the region from the NW, but these features are notoriously hard to predict. Although we are talking about days 5-7, the relatively strong upper flow combined with relative steep mid level lapse rates of up to 7-7.5 C/km would suggest the possibility of severe weather. Instability will certainly not be a limiting factor as temps warm into the 80s and 90s every day. At this time, the synoptic pattern for severe looks most favorable Thursday with an approaching trough and the most robust CAPE. The CSU Machine Learning Probabilities have picked up on the aforementioned parameter space and suggest at least a slight risk for severe weather on Wednesday and Thursday for the entire area and Friday for southern/southeast areas. We continue to have plenty of time to monitor this, but the area may become more active by the end of next week. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... As of 145 AM EDT Saturday... Degraded flight conditions are expected to continue through the 06z/04 TAF period as IFR to LIFR CIGs have already overspread the terminals in the wake of a backdoor cold front (with E-NE winds of 10-15 kt with gusts to 20 kt). IFR/LIFR CIGs are expected through much of the night with perhaps some improvement on Sat (to 1000-2000 ft) with continued onshore flow. In terms of precipitation, scattered showers have spread over western portions of the area, and Richmond will likely see brief periods of light rain. Areas of drizzle are also possible through Sat AM. Shower chances continue on Saturday (highest PoPs at RIC w/ lesser chances near the coast). Outlook...Sub-VFR conditions expected at times through the weekend and even into Monday due to an unsettled weather pattern. Scattered showers and tstms are expected on both Sunday and Monday. A warmer, more summerlike pattern returns by Tuesday with chances for storms each afternoon/evening. && .MARINE... As of 710 PM EDT Friday... Key Messages: - Small Craft Advisories have been extended for the Chesapeake Bay and lower James River through Saturday night. - Small Craft Advisories for the seas north of the Virginia/North Carolina border have been extended until 1 AM Saturday. - Winds of 15 to 20 kt with gusts to 25 kt will diminish a bit later tonight into Saturday morning before increasing Saturday. Winds behind the backdoor cold front remain 15-20 kt with gusts to 25 kt this evening (lower across the NC coastal waters). Winds diminish some overnight but should still gust to 20 kt through the night. Winds ramp back up Sat afternoon into Sat night with gusts to 25 kt. Winds become ESE late Sat night as a warm front lifts N. Waves remain 2-4 ft during this time. Given the gusts to 20 kt between the two surges, have opted to extend SCAs through Sat night to account for both surges for the Ches Bay and Lower James. Additionally, with seas of 4-6 ft this evening N of the VA/NC border and persistent E flow, seas should be slow to subside to 4 ft tonight. As such, have extended SCAs for all coastal waters N of the VA/NC border until 1 AM Sat. The front lifts back N on Sunday, shifting winds to the SE/SSE. SSW winds return for Monday through the middle of next week (but likely remain sub-SCA).Southerly flow looks as though it will persist through most of next week with the next backdoor cold front possible some time Friday. && .TIDES/COASTAL FLOODING... As of 905 PM EDT Friday... Have maintained a Coastal Flood Statement for locations in the upper Bay as tides increase and stay just shy of minor flood stage overnight. Tidal anomalies continue to increase this weekend with minor to locally moderate flooding (at Bishops Head) possible across the middle and upper bay due prolonged onshore flow. Nuisance to minor flooding is possible up the James River as well Sat evening. Will likely need to upgrade the Coastal Flood Statement to a Coastal Flood Advisory across parts of the upper Bay for the Sat afternoon high tide. However, given that the upcoming high tide stays just below, will hold off for now. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 7 AM EDT Sunday for ANZ630>632-634. Small Craft Advisory until 4 AM EDT Sunday for ANZ638. Small Craft Advisory until 4 AM EDT early this morning for ANZ650-652-654-656. && $$ SYNOPSIS...SW NEAR TERM...SW SHORT TERM...SW LONG TERM...AM/SW AVIATION...AM/ERI MARINE...LKB/RMM/JAO TIDES/COASTAL FLOODING...