####018007961#### FXUS62 KCHS 082046 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 446 PM EDT Wed May 8 2024 .SYNOPSIS... A cold front will approach the area Thursday night, then move offshore Friday. High pressure will prevail for the weekend into early next week. A storm system is possible by the middle of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... This evening and tonight: High pressure will continue to extend westward into the forecast area through the overnight. We currently expect the area to remain dry through the overnight, but can't completely rule out an isolated shower or thunderstorm brushing the northern tier of the area later this evening or overnight. This would primarily be an issue for northern Dorchester or Berkeley counties. This potential hinges convection developing across the Midlands and drifting further south into the northern reaches of Dorchester or Berkeley. The overall chance looks low which is why the forecast is dry, but certainly not out of the realm of possibility. Skies should remain mostly clear, other than some cirrus debris potentially passing through. It will be a very mild night, with most areas not falling below 70. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Thursday and Friday: The mid-levels will consist of zonal flow over the Southeast U.S. Thursday morning. A shortwave will be embedded in the flow, moving over our area Thursday afternoon or evening. Troughing will strengthen over the Great Lakes Region on Friday, with amplification expected down towards our region by late Friday. At the surface, Low pressure will be near the OH Valley Thursday morning. This Low will gradually shift eastward with time, moving off the Mid-Atlantic coast by late Friday. A cold front attached to the Low will approach from the northwest Thursday. It'll be located just to our northwest early Friday morning. The front should slowly move through our area from northwest to southeast Friday afternoon, shifting offshore Friday evening. The main focus will be the severe potential Thursday, followed by possibly a second round on Friday. Thursday morning should be dry, with any convection going on well to our west. This line is expected to shift eastward during the day, and into our area. There will be a deep plume of moisture ahead of this line with PWATs rising to ~2". This is well above normal for this time of year, above the 90% mark for CHS per the SPC Sounding Climatology. In addition to this moisture will be above normal temperatures. Highs will peak in the lower to middle 90s, which is near record values for this date. So there will be plenty of moisture and heat in place across our area, which will be supportive of severe thunderstorms. MLCAPE values should peak in the 1,500-2,000 J/kg range. Lapse rates will be steep, especially in the lower levels, Additionally, nearly unidirectional 0-6 km shear should be in the 40-50 kt range. So the main threat will be damaging winds, possibly widespread, large hail, and maybe even an isolated tornado. The SPC has upgraded portions of our area to an Enhanced risk, and this seems reasonable given the environmental setup. The main question will be the timing and evolution of the storms. The CAMs have a MCV moving through our area, ranging from the very late morning through the afternoon. The synoptic models also hint at this, more towards the later afternoon. Since any lines of convection tend to move faster than the models, we're anticipating it to reach our far inland counties early in the afternoon, making it to our coastline by later in the afternoon, then offshore by the evening. The line will be moving at a decent speed, so the severe threat at any one location should only be around for maybe an hour or two. In addition to the already mentioned hazards, locally heavy downpours are expected, with flooding possible in the typical low-lying and poorly drained areas. But the risk of widespread areal flooding is low. Once the convection moves through, their should be some remnant showers persisting into the evening, with a potential lull for a brief time overnight. Then, another round of convection is possible Friday morning into the afternoon. The models are starting to hint that the instability and moisture setup could be similar on Friday compared to Thursday. But this doesn't mean that we'll have identical severe impacts on Friday. What happens on Friday will depend partly on what happens Thursday. The SPC has our area under a Marginal Risk for severe weather on Friday, and this seems reasonable. We wouldn't be surprised if it got upgraded further. Otherwise, we have likely POPs for most of the day Friday with high temperatures near normal. Convection will finally end from inland to coastal locations Friday evening, as the front moves through. Friday overnight is expected to be dry. Clearing skies will yield temperatures from the mid 50s far inland to the lower/middle 60s along the immediate coast. Saturday: Mid-level troughing will persist over the East Coast. High pressure will build in from the west, bringing much drier conditions. Expect mostly sunny skies with highs in the upper 70s to lower 80s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... High pressure will bring dry conditions and seasonal temperatures this weekend through early next week. Models then suggest that a storm system could move across our area starting late Monday and possibly lasting through Wednesday. There remains uncertainty in the models, so we didn't stray away from the blend, which has a period of likely POPs. But this aspect of the forecast will need to be adjusted with future updates. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 18z Thursday. Any Thursday thunderstorm activity is expected to arrive after 18z at the TAF sites. Extended Aviation Outlook: A front will bring periods of flight restrictions Thursday afternoon through Friday. Convection is most likely Thursday afternoon, with very strong winds possible. VFR will return for the weekend. && .MARINE... Tonight: Winds will remain 10-15 knots with gusts to 20 knots (and a few gusts approaching 25 knots) will continue along the land/sea interface into the early evening hours. We will maintain enough gradient overnight to yield elevated south to southwest flow across the local waters. A solid 15-20 knots is expected for periods of time. Seas will increase, becoming 2-4 feet on average, and up to 5 feet in the outer Georgia waters. Thursday through Friday: A strong cold front will approach Thursday causing SW winds to increase. Marginal Small Craft Advisory conditions are expected across our Charleston waters Thursday afternoon and evening due to gusts around 25 kt, and again Friday night behind the front. Additionally, there will be the potential for strong thunderstorms Thursday afternoon and evening, following by a second round Friday late morning or afternoon. The timing of thunderstorms remains unclear, but any storms that do develop and move across the waters will be capable of producing strong wind gusts. Saturday through Monday: Marine conditions will rapidly improve this weekend as weak high pressure builds in from the west. By Saturday, winds will drop to 10-15 kt and seas to 3 ft or less through Monday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM... LONG TERM... AVIATION...BSH MARINE...BSH ####018004541#### FXUS63 KLSX 082047 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 347 PM CDT Wed May 8 2024 .KEY MESSAGES... - Scattered strong to severe thunderstorms will persist through early this evening. All hazards are expected: large hail, damaging winds, isolated tornadoes, as well as flash flooding. - A period of much needed calmer weather and cooler temperatures is expected to end the week and continue through the weekend. && .SHORT TERM... (Through Late Thursday Night) Issued at 344 PM CDT Wed May 8 2024 (Late This Afternoon Through Tonight) As of 3 pm, outflow from the activity continues to sink south and extends from just north of Springfield, MO to just south of Carbondale, IL. The warm sector along and south of the boundary remains quite unstable with MU CAPEs in excess of 3000 J/kg, ML lapse rates of 7-8C/km and 0-6km bulk shear 50-60kts. Also, the ongoing activity, over far southeastern sections of CWA, has congealed into a line with embedded supercells, while further west, in NWS Springfield's area, discrete supercells are forming along the outflow boundary. These storms will slide east northeast moving into the southern portions of the CWA by 21z. Therefore, there remains a tornado threat as well as large hail possible. North of the outflow boundary, could see scattered strong to severe storms with the main threat being large hail. Otherwise, as the surface low over NE OK lifts northeastward it will drag a cold front eastward through the forecast area, with the precipitation tapering off from west to east. The front will exit the region by 05z Thursday. Still some concern for isolated flash flooding as some storms may train over the area, especially south of I-70. So will not make any adjustments to the Flash Flood watch at this time. Lows tonight will be in the low 50s to low 60s. (Thursday through Thursday Night) On Thursday, a secondary shortwave/cold front on the backside of the system will slide southeast through the region. So expect increasing clouds, especially north of I-70. Otherwise, there will be enough moisture and weak instability to generate scattered showers and a few thunderstorms over portions of northeast Missouri and west central Illinois late morning through early evening. Otherwise, highs on Thursday will be near normal in the upper 60s to upper 70s. Lows Thursday night will be in the upper 40s to low 50s. Byrd && .LONG TERM... (Friday through Next Wednesday) Issued at 344 PM CDT Wed May 8 2024 Cooler and drier weather through the rest of the work week and into the weekend. Beyond that, upper level trough over the western CONUS will begin to lift out towards the region with chances of showers and storms late on Sunday through mid week. Still a lot of timing, strength and location differences among the ensembles and deterministic models, so stuck with the latest NBM solution. Temperatures will moderate through the period with highs in the mid 70s to low 80s. Byrd && .AVIATION... (For the 18z TAFs through 18z Thursday Afternoon) Issued at 1252 PM CDT Wed May 8 2024 Severe storms staying south of TAF sites at this time, but could see storms move through St. Louis metro area TAFs between 18z and 00z Thursday. For KCOU and KJEF, just kept vicinity shower/storm mention through the afternoon hours. With the stronger storms could see brief periods of MVFR ceilings and visibilities, otherwise VFR flight conditions. By this evening as cold front moves through, winds will veer to the southwest to west by 05z Thursday at KCOU and KJEF and by 07z Thursday at KUIN and St. Louis metro area TAF sites. Also, wrap around MVFR ceilings will move into KUIN by 03z Thursday and persist through the remainder of the forecast period. Winds will pickup by mid morning from the northwest with gusts up to 25 kts at times. Byrd && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Flood Watch until midnight CDT tonight for Cole MO-Crawford MO- Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Madison MO- Moniteau MO-Osage MO-Reynolds MO-Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-Washington MO. IL...Flood Watch until midnight CDT tonight for Monroe IL-Randolph IL- Saint Clair IL. && $$ WFO LSX ####018006757#### FXUS65 KPIH 082048 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 248 PM MDT Wed May 8 2024 .SHORT TERM...Tonight through Thursday night. Remnants of the deep upper low refuse to give up impacting East Idaho with trough draped east-west across the state this afternoon. Mainly isolated showers remain possible through early evening as moisture works around the low and drops into East Idaho from Montana. Gusty northerly downslope winds are draining out of the Central Mountains and off the Divide, supporting slightly warmer but breezy conditions continuing tonight. Elsewhere through the Snake Plain, the downslope conditions are not quite as strong, so temperatures around/less than 36F are expected, supporting another night of Frost Advisory. Models support the trough dropping into Utah and briefly closing off over the Great Basin Tuesday, allowing the wrap around moisture to shift across mainly the southern highlands during the day. Thus showers and isolated thunderstorms will be possible mainly across the southern and southeast highlands in the afternoon. The gusty northeast gradient will continue, with the strongest winds centered across the Arco Desert region. Wind speeds may be marginal for Wind Advisory but hoisted the headline anyway as the northeasterly direction may catch drivers off guard along US-20 and US-26, especially those that commute those routes routinely. Northeasterly gradient continues into Thursday night, but slackens considerably. Strong possibility that one more Frost Advisory will be needed, particularly along zones containing the I-15 growing corridor. Could see a few pockets of fog in protected valley regions, and have retained the previous forecast. DMH .LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY... This portion of the forecast continues to resemble a lunchmeat sandwich as an elongated W-E zone of low pressure...the leftovers of the active wx we've been munching on for days...sinks southward across the Four Corners region to central Plains, and a "tongue" of high pressure noses in on top of it eastward across the nrn Rockies from the Pacific. This overall synoptic configuration should whet our appetites for spring w/ drier conditions and a strong warming trend Fri-Sat-Sun with highs by Sun ranging from about 70 to 80 degF for most lower elevation population centers, but the proximity of low pressure to our south is close enough that we can't completely rule out some limited coverage of at least isolated afternoon shower/t-storm activity down across some of our SE highlands into Bear Lake, as reflected by light PoPs carried in our forecast courtesy of the NBM. Confidence in coverage of any precip is low, whereas confidence in dry conditions for MOST of the CWA is higher. Compared to this time yesterday, both long-range deterministic model solutions and resultant 500mb height cluster analysis are now a bit more progressive with trying to kick this low pressure zone out to the east by Sun-Mon, with perhaps some trend toward opening up the NW flow storm track and allowing fresh disturbances to take aim at our region during the Mon-Tue-Wed period next week. The strength of Pacific ridging will in part govern whether this storm track will be held further to our N/NE (keeping us dry) or will take better aim at SE Idaho , with the NBM for now brushing our ern highlands and Upper Snake Highlands with light PoPs from time to time and no significant reduction in overall temps. Height clusters are split on this as well. A tightening pressure gradient between the Pacific ridge and this storm track may tend to increase winds over these days, most notable diurnally during the afternoons. For now, no major airmass changes or significant precip events are expected, and we'll need to watch the impact warmer temps will have on mid-high elevation snowmelt and resultant river responses. - KSmith && .AVIATION... The world of aviation is SLOWLY trending less impactful as low pressure just to our east sinks southward and increasingly surrenders synoptic control to a tongue of high pressure nosing in eastward across the nrn Rockies off the Pacific. Showers at KDIJ and VCSH elsewhere continue, but will trend down this eve and end for the night by 02-05z/8-11pm depending on the terminal. Clouds are still widespread but are now VFR everywhere except KDIJ and will slowly rise/thin out as we head into tonight, reaching at least SCT coverage if not FEW. Winds remain breezy but generally not as strong as yesterday, and will relax slightly for the overnight. Biggest challenge through this eve is really to capture the timing as winds evolve from WSW to NNE everywhere but KSUN (which will be a runway crosswind at many airports)...current TAF thinking for this timing is based on a blend of MOS guidance and the latest hourly HRRR, with moderate confidence. Otherwise, main impacts will be occasionally MVFR cigs/vsbys continuing at KDIJ through about 00-01z/6-7pm when most rain/snow showers finally end, and the potential for criteria- borderline LLWS developing at KPIH after about 05z/11pm as sfc winds relax and decouple. This will be almost entirely speed shear as winds should be roughly out of the NE throughout the column. LLWS criteria are not currently expected to be met elsewhere across the forecast area, but this will be monitored. Heading into Thu, still can't rule out a few afternoon showers or even VCTS as departing low pressure is still too close for comfort, but with winds continuing to slowly relax day by day and a continued overall trend toward drier, calmer VFR wx as we round out the week and head into the weekend. - KSmith && .HYDROLOGY... Recent precipitation and warming temperatures are expected to influence East Idaho waterways in the coming days. Whatever snowfall was realized recently at mid-slope is likely to melt off, and temperature profiles support some snow melt at higher elevations. Flood Warnings remain in place for the Blackfoot and Portneuf rivers. High, fast, and cold flows are expected to continue and/or increase on other waterways. As the conditions turn warmer and drier, people recreating on/near East Idaho rivers and streams are urged to remain cautious, and keep children and pets away from the water. DMH && .PIH WATCHES/WARNINGS/ADVISORIES... Frost Advisory from 3 AM to 9 AM MDT Thursday for IDZ051-053-055. Wind Advisory from 10 AM to 7 PM MDT Thursday for IDZ052. && $$ ####018006010#### FXUS65 KTFX 082048 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 248 PM MDT Wed May 8 2024 .SYNOPSIS... Snow and rain will end from northeast to southwest by Thursday morning. Across North-central and Central Montana patchy dense fog is possible this evening through Thursday morning in areas where skies clear. North-central, Central, and Southwestern Montana will dry out and warm up Thursday afternoon through the weekend. By the middle of next week the weather pattern could change. && .DISCUSSION... This afternoon through Thursday... Rain/snow will continue through the evening along the Highway 200 Corridor and south. Precipitation will end from northeast to southwest by Thursday morning. There will also be isolated rain showers across North-central Montana through this evening. Snow will continue along the Southern Rocky Mountain front through this evening. Patchy dense fog has formed in Northern and Central Fergus County and will continue through Thursday morning. At times visibility will be reduced to a quarter mile or less. Patchy dense fog could form in other locations of Central and North-central Montana if skies clear overnight due to all the moisture from this system. A Winter Weather Advisory has been issued for the Madison River Valley and Gallatin Valley until midnight due to snowfall reducing visibility down to a half mile at times. The Blizzard Warning for the Little Belts and Highwood Mountains has been downgraded to a Winter Storm Warning due to the strong winds and wind gusts having ended. The snow has ended for the Highwood Mountains. The Winter Storm Warning along the Northern Rocky Mountain front has been cancelled due to the snow having ended. The Winter Storm Warning along the Southern Rocky Mountain Front has been downgraded to a Winter Weather Advisory. For more details see the TFX WATCHES/WARNINGS/ADVISORIES section below. On Thursday an upper- level trough begins to move out of the area. This will begin to warm up and dry out North-central, Central, and Southwestern Montana. Friday through Sunday... On Friday an upper-level ridge begins to move over North-central, Central, and Southwestern Montana. This will warm temperatures up to about seasonal averages across the area. This upper-level ridge will stay in place above North-central, Central, and Southwestern Montana through the weekend which will keep temperatures dry and allow temperatures to warm up to above seasonal averages across the area through the weekend. Isolated locations of North-central and Central Montana and the Helena Valley have a 50 - 65% chance for having temperatures of 80 degrees or warmer. Monday through next Wednesday... On Monday cluster analysis indicates that there will be upper-level zonal flow over North- central, Central, and Southwestern Montana. This will keep the area's weather about the same on Monday as Sunday. On Tuesday three clusters (86% of ensemble members) have a week upper-level trough over North-central, Central, and Southwestern Montana. One of the clusters (14% of ensemble members) has an upper-level ridge over North-central, Central, and Southwestern Montana. This indicates that the weather pattern could change on Tuesday. Next Wednesday the ensembles begin to diverge and so the weather over North-central, Central, and Southwestern Montana is uncertain at this time. -IG && .AVIATION... 1220 PM MDT Wed May 8 2024 (08/12Z TAF Period) Widespread rain and snow will affect Central ad Southwest MT into the evening hours. IFR or lower conditions will also occur. Conditions slowly improve overnight, as the showers become more scattered. However, with any clearing, there is the possibility that some fog could develop. Overall, mostly VFR conditions are expected by 18z Thu for most areas. Mountains/passes will be obscured through late Thu morning. Brusda Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .HYDROLOGY... The flood warning will continue for Clear Creek, as the creek has risen into major stage earlier today. Additional runoff from the Bears Paw Mountains will continue to produce minor flood impacts from other small streams and creeks, such as Big Sandy Creek and Beaver Creek. Areas of minor flooding have been reported around Beaver Creek, along with locations around Hays and Lodge Pole. Thus the areal flood advisory will continue for portions of North Central MT until Thursday afternoon. For areas further south and west, most of the higher elevations have had just snowfall recently, thus runoff from the recent snowfall will begin in a few days as warmer air moves back in. Since most river levels are currently low, impacts should be minor from any new flooding that develops. Brusda && .PRELIMINARY POINT TEMPS/POPS... GTF 34 56 34 64 / 80 40 0 0 CTB 31 59 33 70 / 10 0 0 0 HLN 40 58 37 70 / 60 30 0 0 BZN 34 55 31 64 / 70 50 10 0 WYS 30 53 26 61 / 40 30 0 0 DLN 37 56 34 66 / 50 20 0 0 HVR 41 66 38 70 / 40 20 0 0 LWT 32 48 31 58 / 90 50 10 0 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until midnight MDT tonight for Southern Rocky Mountain Front. Winter Storm Warning until midnight MDT tonight for Big Belt, Bridger and Castle Mountains-Gallatin and Madison County Mountains and Centennial Mountains-Snowy and Judith Mountains. Winter Weather Advisory until midnight MDT tonight for Gallatin Valley-Madison River Valley. Winter Storm Warning until midnight MDT tonight for Little Belt and Highwood Mountains. && $$ http://www.weather.gov/greatfalls