####018010296#### FXUS63 KLMK 032315 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 715 PM EDT Fri May 3 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Isolated shower and thunderstorm possible this afternoon. Slow moving storm motion and moderate to heavy rain expected with any storm. * Showers and thunderstorms will be more scattered on Saturday, though forecast confidence in exact timing and coverage remains low. * Increasing potential for strong to severe thunderstorms and flooding next Tuesday through Thursday, though confidence in details is still low. && .MESOSCALE... Issued at 527 PM EDT Fri May 3 2024 A north-south oriented line of convection stretching from Larue Co through Hart, Barren and Monroe will continue to work east-northeast this evening. This activity is forming along an inverted sfc trough and theta E axis and moving along a MLCAPE gradient. Per the KY Mesonet, dew points along and ahead of this sfc trough were in the upper 60s to near 70, while to the north they were in the low/mid 60s. Main impacts from these storms will be brief heavy downpour and lightning. Wind gusts have been 10 to 15 mph with maybe a gust approaching 20. Overall impacts remain low. The bulk of the thunderstorm activity should remain mainly south to just along the parkways. To the north, off and on light showers will continue with little to no lightning chances. Rain and storms will diminish from the northwest to the southeast later this evening and overnight. && .SHORT TERM /THROUGH SATURDAY/... Issued at 328 PM EDT Fri May 3 2024 ========== This Afternoon ========== The cold front is located just north of the Ohio River this afternoon, with our area within the warm sector of the system. Mostly cloudy sky cover has kept temps cooler than in previous days, with highs so far in the low 70s. However, the airmass is muggy enough to develop some marginal instability, with ACARS data from SDF showing over 500 J/kg of MLCAPE. Convective temps are close to the mid 70s, so if we can reach another degree or two we could see isolated convection fire up along the front or in the warm sector. We are already seeing some showers redevelop down towards Bowling Green, as well as along the front closer to Huntingburg, IN. Probability of thunder for this afternoon peaks around 50%, so coverage will be mainly isolated, and not everyone will see a thunderstorm. For those that do see storm activity in the next few hours, moderate to heavy downpours will be expected thanks to the PWATs around 1.5 inches. Additionally, very weak flow and shear will promote unorganized and very slow storm motions in addition to the lightning threat this afternoon. ========== Tonight ========== Around sunset and into tonight, precip coverage will begin to diminish as our daytime heating is lost. The cold front appears to wash out tonight, leaving no real source of lift in place. However, those high PWATs will linger, so will need to keep at least a slight chance through the night. However, better chances for additional showers come in the morning hours. Temps will be mild tonight, with lows only reaching the low to mid 60s. With the muggy airmass in place, and saturated grounds from recent rains, there should be a good chance for low stratus and fog tomorrow morning. After sunrise, stratus and fog will burn off. ========== Saturday ========== Another weak mid-level impulse should lift northeast from the south into the region tomorrow morning. This will bring additional rounds of isolated to scattered showers in the morning, with the greatest chances to the east of I-65. The forecast for tomorrow afternoon remains complicated in regard to shower and storm activity without much of a trigger mechanism in place. As mentioned earlier, the cold front will have washed out, leaving behind a moist and unstable airmass across the region. There will likely be some weakening mid-level vorticity left over from the morning impulse from the south, but overall the greater forcing will be up towards the Great Lakes later in the day. It'll be another muggy day, with dewpoints possibly reaching the upper 60s, with 12z HREF favoring 75-80% chance for dewpoints over 65F. PWATs don't appear to be as high as today, but still between 1.25-1.4" possible. However, sfc temperatures will be much warmer with highs hitting the upper 70s and possibly even the low 80s in some locations. This should lead to more potential instability during the afternoon, with forecast soundings suggesting between 1000-2000 J/kg of SBCAPE possible. Convection initiation tomorrow afternoon will probably be driven by differential heating boundaries or other mesoscale features present at the time. Due to this continued uncertainty, will continue with broad brush PoPs for the entire region. Severe thunderstorms are not expected due to another day of weak flow aloft. Storms that do form will be fairly slow movers, with storm motions generally less than 20 mph expected. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 328 PM EDT Fri May 3 2024 Synopsis...The medium-range forecast starts on Sunday by featuring an expansive mid-level ridge over the central and eastern US as mid- level shortwave energy lifts from Upper Midwest to Canada. Further west, a strong mid- to upper-level trough will move onshore from the Pacific eventually amplifying across the western two-thirds of the country by the middle of next week. The ensuing broad cyclonic circulation will allow the upper jet to stretch closer to the Ohio Valley while periodic shortwave energy rotate around the trough axis. As a result, there is a chance of organized, strong to severe storms for several days next week across the Lower Ohio Valley as the main trough meanders around the Plains. Model Evaluation/Confidence...Confidence in synoptic weather pattern has continue to increase as CMC/ECMWF/GFS deterministic models agree fairly well on the position and evolution of the main features (trough/ridge). On the other hand, confidence decreases in the timing and intensity of individual shortwave troughs embedded within the larger trough circulation impacting the ability to indicate the exact times of the severe weather risks. Nonetheless, the CSU and NCAR machine learning algorithms have been consistent at depicting, at least, low probabilities of severe weather for the Tuesday- Thursday timeframe. Sat Night - Sunday...A slight chance of showers and storms will continue Saturday night into sunrise on Sunday as a weak frontal boundary approaches the area overnight. The second half of Sunday morning and early afternoon looks drier as the diffuse boundary stalls close to the Ohio River. Another low chance of showers and storms might be in place late Sunday afternoon and early evening ahead and along the frontal wave provided that cloud coverage diminishes and solar radiation destabilizes the BL to yield CI once convective temperatures are met. Given the weak steering flow, mesoscale boundary interactions could play an important role for convective initiation and maintenance. Sun Night - Monday...An increase in shower intensity and coverage can be expected Sunday night into Monday morning as a southern- stream shortwave trough moves from the southern Plains to the Ohio Valley. GFS forecast soundings show increasing moisture profile with overall decreasing instability and warming mid-level temperatures. Therefore, there could be a chance of brief moderate to heavy rainfall with low thunder probabilities. This vorticity wave will push the stalled frontal boundary further north, so the shower coverage should decrease towards the afternoon and evening given the lack of any substantial forcing mechanism. Tuesday - Friday...As mentioned above, chances of strong to severe storms will be on the rise during the Tuesday-Thursday timeframe owing to the increasing shear associated to the incoming upper jet, the presence of moderately high instability values, and sufficient forcing provided by the periodic mid-level shortwave troughs. Although confidence in timing and details on type of severe risk are low at the moment, available medium-range CAM guidance (GFDL-SHIELD) hint at a multi-day overnight severe threat on Tue and Wed night with probabilities displaced further south for Thu night. A flooding risk cannot be ruled out either given the convective nature and duration of the weather events. && .AVIATION /00Z TAFS THROUGH 06Z SUNDAY/... Issued at 714 PM EDT Fri May 3 2024 Weak area of low pressure was located just west of KFTK this hour and will continue to move east-northeast this evening. Cold front remains northwest of the KSDF/KBWG/KLEX/KRGA terminals and will slowly move SE this evening. Cigs across the region have remained generally VFR with some tempo drops to MVFR in passing showers. Later this evening and into the overnight period, the cold front will slowly washout over the region leaving light winds and relatively moist boundary layer. Much of the guidance suggests that low clouds/fog/mist will likely develop with cigs falling through the MVFR range and then into the IFR range overnight. Vsbys look to remain mostly MVFR but IFR/LIFR vsbys may develop at KBWG late tonight. Cigs/vsbys should come back up in the 04/13-14Z range with skies eventually returning to VFR by late morning. For tomorrow afternoon, a bit more heating will take place and scattered showers and a few storms will be possible across the region. So will continue the VCSH mention in the new TAF package. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ MESOSCALE....BTN SHORT TERM...CJP LONG TERM....ALL AVIATION.....MJ ####018005876#### FXUS65 KRIW 032315 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 515 PM MDT Fri May 3 2024 .KEY MESSAGES... - Snow ends this afternoon, with a clearing sky overnight. Patchy fog is possible (20%) for basins and near Casper due to recent moisture (snow). - High pressure Saturday brings warmer temperatures and dry weather. Warmer Sunday. - Gusty south wind Sunday. Gusts 30 to 50 mph for most of the area. Strongest winds over southern Sweetwater County, with high winds (gusts greater than 58mph) likely (80%). Impacts to I-80 and South Pass due to strong crosswinds. - Precipitation moves in Sunday, with widespread precipitation Monday. Snow levels drop to around 6000 feet. Cool and unsettled weather pattern through next week. && .DISCUSSION... Issued at 1238 PM MDT Fri May 3 2024 Snow has been falling across the area this morning as a cold front passes through. As the sun rises through the afternoon, any snow that has accumulated on grass should melt quickly. Clouds linger through the rest of the day, limiting high temperatures today. Many places peak in the upper 40s today, with the Bighorn Basin seeing a few places hit 50. These temperatures are roughly 10 degrees below normal. Any remaining precipitation comes to an end by around 03Z (9pm). As the trough moves eastward tonight, transitory ridging builds in for the weekend. Starting with Saturday, the day brings warm temperatures and a mainly clear sky (a stark difference from today). High temperatures for many reach the mid-to-upper 60s, with a few places hitting 70. A slight breeze develops in the afternoon (10-25 mph gusts), but should otherwise be a good day for any outdoor activities or chores. The high pressure shifts eastward for Sunday as a potent upper-level low swings into the northern California area. This brings a tight pressure gradient, as well as a 100 knot jet positioned into southern Sweetwater County. A strong south wind develops after sunrise, and especially for the afternoon and evening across Sweetwater County, northward into most of the CWA (exception being far northwest Wyoming). Where the exit region of the jet is (southern Sweetwater County), gusts up to 70 mph are possible if the upper levels are able to fully mix down. Shift of tails highlights this area in the 90th percentile. Elsewhere, widespread gusts 35 to 50 mph occur. Being a south wind, roads like I-80, South Pass/Red Canyon, and US-26 will be impacted as strong crosswinds occur. Precipitation chances move into western Wyoming Sunday morning, spreading east of the Divide for the afternoon and evening, with about a 20% chance of thunderstorms. Snow levels begin around 9000 feet Sunday, but drop to roughly 6000 feet through Monday morning. Therefore, lower elevations are expected to receive mostly rain from this system. That upper-level low moves into the Utah/Idaho/Wyoming area Sunday night and into Monday. Winds begin to shift to a more southwesterly direction, decreasing the gusts some from the day, but gusty winds continue through the night, especially from Sweetwater County up through Natrona County. For Monday, the center of the low is projected to move across Wyoming, then traveling northeastward near the Montana/North Dakota border. The GFS and ECMWF vary a bit in placement on this. Widespread precipitation occurs Monday. The heaviest precipitation will be where favored upslope occurs. Currently, this would be for the Bighorn Mountains and Johnson County, but as mentioned, there is still some uncertainty in exact storm track, which could alter where the best precipitation totals are favored. Will need to watch closely the next few days on where models agree on the storm track. The low is slow to move, as ridge over the eastern half of the country keeps it mostly in place. This would keep precipitation chances over the area Tuesday, especially over the northern half of Wyoming. Currently, models are keeping the influence of the low through Friday, so a cool, cloudy, and unsettled next week is in store. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 515 PM MDT Fri May 3 2024 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals. VFR to prevail at all terminals through 00Z/Sunday. Mid-cloud cover gives way to a clearing sky early Friday evening as an upper low tracks southeast of the forecast area. Mainly high clouds and a few cumulus over the higher terrain Saturday. Gusty west to northwest wind 15-25kts on the backside of the upper low Friday afternoon decreases between 01Z-03Z/Saturday. Southerly wind around 10kts increases late Saturday morning and early afternoon. Mountain tops occasionally obscured above 10K feet MSL until 02Z/Saturday. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals. Mid-cloud decks gradually diminish between 00Z-02Z Friday evening, leaving a clearing sky overnight. Boundary layer moisture is sufficient to at least generate patchy fog at KCPR, KRIW, and possibly KLND between 10Z-15Z/Saturday. The best chance for MVFR fog comes at KCPR during this window, as the late clearing, lack of wind, and abundant low-level moisture favor formation. The fog clears between 14Z-16Z/Saturday, leaving only high clouds and a few mountain cumulus through Saturday afternoon. Mountain tops obscured until 02Z/Saturday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wittmann AVIATION...Jones ####018006320#### FXUS61 KGYX 032318 AFDGYX Area Forecast Discussion National Weather Service Gray ME 718 PM EDT Fri May 3 2024 .SYNOPSIS... High pressure near the coast will provide dry conditions through Saturday, with increasing onshore flow this weekend. Thickening clouds, cooler temperatures and rain showers are expected by Sunday as the high drifts north. Clearing likely not coming until Monday behind a passing cold front. Warmer and sunnier conditions are expected into Tuesday, then more unsettled weather returns around the middle of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 7:15pm Update... No notable changes with this update as the forecast remains on track. Updated temps and dew points based on trends and the latest high res guidance this evening. Patchy fog still looks on track tonight as only high cirrus filters through, and moisture increases through the low levels. Previous... Satellite imagery this afternoon shows a cu field over the region along with some passing cirrus. There continues to be breaks in this cloud cover though, which has allowed temperatures to warm into the lower to middle 60s in most locations, although mainly in the 50s along the coast due to weak onshore flow. It will continue to be a dry afternoon and evening with temperatures cooling into the 50s areawide. A positively tilted h5 ridge axis will remain overhead tonight with partly to mostly cloudy skies but continued dry conditions. Patchy fog is possible overnight depending on cloud cover but the latest HREF suggests this likely won't bring visibilities below 1 mile in most locations. Overnight lows will range from the upper 30s across the north to the lower and middle 40s south. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... The mid-level ridge axis remains overhead on Saturday with sfc low pressure over the Gulf of Maine. Partly sunny skies during the first half of the day will likely become mostly cloudy by the afternoon as a weak vorticity maximum crosses. Light and variable winds combined with daytime heating will likely result in a seabreeze. Highs will range from the lower to middle 60s across the interior with cooler 50s along the coast. Surface high pressure will begin to retreat to the northeast Saturday night but the h5 ridge axis will remain overhead. Other than a stray shower over western NH towards dawn it will be another dry night with patchy fog once again possible. Low temperatures will primarily be into the 40s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Overview: Unsettled weather expected for the second half of the weekend as a cold front nears Sunday and passes Monday morning. High pressure and warm temperatures arrive the latter part of Monday, continuing into Tuesday. Additional unsettled weather is expected mid to late week as broad low pressure moves into the eastern Great Lakes. Details: Onshore flow will be underway Sunday with mostly cloudy skies. Skies will be more overcast to start the day across NH, mainly as the area sees greater moisture advection ahead of approaching cold front. There is some uncertainty on daytime highs Sunday, mainly due to this onshore flow and increasing cloud cover. Went on the cooler side of guidance for now, but current forecast spread for high temps varies by 5 to 7 degrees across much of the area. Rain will arrive with the cold front in the evening, beginning as showers and then more persistent rain overnight. Rainfall amounts should remain around a quarter inch or less, but some showers could enhance local amounts higher than this value. The associated cold front begins to lose its deeper moisture as it tracks into New England, as probabilities for greater precipitation lie to the west. Perhaps some remaining drizzle along the coast early Monday morning, but drying across the CWA should be underway by mid morning. NW breeze will also kick up to enhance drying through the afternoon. Should this stay on track, temperatures will be in for a rebound later in the day with highs in the 70s possible for southern NH and into southern Maine's interior. Tuesday follows up as warm and dry, before another period of unsettled weather for mid to late week. Current NBM PoPs are likely overdone due to the wide spread of guidance solutions, and have tried to emphasize this uncertainty by keeping just a chance of rain to close out the week. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/... Short Term...VFR conditions will persist through much of tonight, although pockets of MVFR to locally IFR restrictions are possible late due to lower ceilings and FG. Mainly VFR conditions are then likely after 15Z Saturday, although pockets of MVFR are possible, especially at coastal TAF sites. Ceilings will then gradually lower again Saturday night with potential patchy fog. Light and variable winds tonight through Saturday morning will become southeasterly later Saturday before becoming light and variable again Saturday night. No LLWS is expected. Long Term...MVFR skies start the day Sunday, perhaps lifting to VFR in the afternoon. However, general trend will be back to MVFR/IFR Sun night into Monday morning. Rain and fog may cause vis restrictions overnight. Ceilings should improve to VFR at all terminals into Monday afternoon through Tuesday. && .MARINE... Short Term...Winds and seas to remain below SCA thresholds through at least Saturday night with high pressure over the waters. Light and variable winds tonight will become southeasterly on Saturday. Long Term...Conditions should remain below SCA criteria through Wednesday, but there may be periods of visibility restriction Sunday and Sunday night in fog amid onshore flow. Winds increase overnight as a cold front nears. The cold front will pass over the waters Monday morning, bringing better vis conditions through Tuesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Clair SHORT TERM...Tubbs LONG TERM...Cornwell