Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/26/21

Area Forecast Discussion
National Weather Service La Crosse WI
1015 PM CDT Thu Mar 25 2021 .SHORT TERM...(This evening through Friday) Issued at 218 PM CDT Thu Mar 25 2021 At 130 PM, skies were partly to mostly cloudy, with spotty light rain showers noted over parts of northeast Iowa into southwest Wisconsin. Winds were beginning to turn more northeasterly ahead of surface low pressure located in Missouri. The aforementioned surface low will continue to eject northeastward through Illinois and into southeast Michigan this afternoon/tonight, with good consensus that the heavier wrap around precipitation stays to our southeast where the better forcing will be. However, high resolution guidance continues to show light rain from northeast Iowa into southwest and even central Wisconsin through this afternoon and evening on the fringe of the shortwave forcing and in the vicinity of some mid-level frontogenesis. Given this, will maintain PoPs in this area. As temperatures cool into the 30s by late evening, a few snowflakes could mix in east, but not expecting accumulations given light precipitation and a relatively warm ground. The RAP does suggest saturation is slow to decrease tonight, so there could be a period of drizzle following the rain, but forcing looks to wane as the night wears on. Friday looks like a dry day, as ridging builds into the area. Models disagree on how quickly cloud cover diminishes, however, with the RAP suggesting low-level moisture gets trapped and clouds linger all day long, whereas other guidance would have skies scatter out tonight or early Friday morning and bring a sunnier day for Friday. For now, will lean toward the sunnier forecast with clouds being more scattered/diurnal in nature thus far this afternoon. .LONG TERM...(Friday night through Thursday) Issued at 218 PM CDT Thu Mar 25 2021 The next chance for precipitation still looks to be on track for Friday night into Saturday night. A long wave trough is currently taking shape over the western conus as several short wave troughs move onshore from the northern Pacific. One of the lead short wave troughs will advance northeast across the region Friday night and Saturday followed by another short wave trough coming in from the northwest Saturday night in the mean long wave trough. These waves look to produce a couple rounds of weak to moderate pv advection in the 500-300 mb layer as they move across. A weak area of low pressure should develop over southwest Kansas Friday and then advance northeast across Iowa into eastern Wisconsin Friday night and Saturday. Decent warm air advection ahead of the low will produce 2 to 4 ubar/s of up glide on the 290K isentropic surface. With some weak moisture transport occurring in conjunction with this warm air advection/isentropic up glide, the column is expected to quickly saturate with precipitation spreading over much of the area late Friday night. A band of weak mid-level frontogenesis should form on the northwest side of the surface low Saturday afternoon and combine with the forcing from the second short wave trough to maintain some precipitation into Saturday evening. Temperatures look to be warm enough for most of this to fall as rain. The possible exception to this will be along the leading edge of the precipitation Friday night as it moves into the Interstate 94 corridor. Temperatures there look to be cold enough for some light snow to initially occur. Also not completely out of the question is a short period of some light freezing rain if dew points are slow to rise before the precipitation moves in. This should not last very long if it does occur, but a light glaze is not out of the realm of possibilities. As for whether there is still a chance for some light precipitation early next week remains rather murky. The 25.00Z ECMWF and 25.12Z GEM still suggest a piece of energy will drop out of the southern end of the long wave trough over the weekend and then move northeast early next week. These models have shifted this short wave trough farther southeast and more into the Ohio River Valley than yesterday`s solutions. The 25.12Z GFS has gone away from this idea and does not drop any energy out of the long wave trough over the weekend and thus does not have any system advancing northeast early next week. After that, a cold front should advance through the area Tuesday ahead of a positive tilt long wave trough in association with an upper level low advancing east across central Canada. Some light precipitation could occur along and behind the front Tuesday and Tuesday night. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1015 PM CDT Thu Mar 25 2021 Cigs: low cloud potential a lot more unclear at late evening, with northward advancement having slowed and meso models not as bullish. RAP/HRRR/NAM12 all show different things and don`t capture current conditions very well. Latest trends do lean toward KRST staying just north of MVFR while KLSE might still get into it for a time overnight. Confidence not very high and anticipate adjustments as the night wears on. Meanwhile, ribbon of low level saturation for the afternoon should result in sct-bkn cu deck...and a few hours of MVFR possible. Will hold scattered for now. High/mid clouds on the return Fri night ahead of shortwave trough lifting northeast out of the southern plains, and then back into MVFR for much of Sat. WX/vsby: no impacts anticipated. Winds: light and northerly tonight, staying light with a shift to more south/southwest Friday afternoon. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Lee LONG TERM...04 AVIATION...Rieck
Area Forecast Discussion
National Weather Service Birmingham AL
652 PM CDT Thu Mar 25 2021 .UPDATE... Evening Update and 00Z Aviation. && .SHORT TERM... /Updated at 0624 PM CDT Thu Mar 25 2021/ Long track damaging tornadoes have moved across Central Alabama this afternoon. Significant damage has taken place. At this writing, no tornado warnings are in effect. A Tornado Watch remains in effect until 8 pm and may be extended. So what now, a warm front was located just north of the area while a cold front/trough was still back to the west. The latest RAP analysis has SBCAPE values still over 2000 and will become even more suppressed to the southern reaches the next few hours. A rain induced boundary or axis of a mixed up atmosphere was west to east across Central Alabama from TCL to ANB. SRH values will slowly go down as the low level jet exits northward. So at this time, it appears the greatest threat will reside south of a line from Sumter County to Randolph County. The threat north of this area is certainly not zero, and will keep a mention of severe storms including tornadoes, but the threat is lower than earlier this afternoon. So will make some changes to the graphics suite but the overall trend in the forecast looks ok. 75 Previous short-term discussion: /Updated at 450 AM CDT Thu Mar 25 2021/ Today through Friday. So far this AM we have had widespread showers with embedded thunderstorms as it spread NE across C AL. The activity has been elevated and while we are watching for any rogue storms, severe activity during the early morning hours should be marginal at best until the warm front makes its way northward later today. We have increased the severe threat in the NW half of C AL for this afternoon and evening. This probably doesn`t come as much of a surprise as this system is ramping up to be significant there with strong tornadoes a possibility. The SE half of C AL is a different story. While we have a marginal threat this AM for portions of C AL, for the rest of the afternoon and evening, parameters are much lower in the SE counties with convection not as likely there until later this evening. After the current convection currently on the radar pushes N, we should have a somewhat lull in activity in the SE. In contrast, by around 11am, our warm front should be to the N of the area. Models suggest some cellular activity will likely pop up in the NW first. MUCAPE will not be lacking, but will be highest in the west for this afternoon. 0-6km bulk shear will be in ample supply across C AL. However, 0-1km shear will be decidedly higher in the NW. Although amounts vary, guidance is in agreement decreasing this low level shear significantly after 6z as the bulk of the instability skirts to the NE. This will be not only with the front moving across, but our negatively tilted upper shortwave that is expected to be over the Arklatex ~18z today expected to race off toward IL/IN by midnight tonight. With the bulk of the activity in the SE counties expected for later this evening, this greatly decreases the chance for severe weather for them S of the I85 corridor. This is the reason for the sharp risk gradient in our severe graphics. Timing is pretty similar to what we had yesterday except possibly starting in the NW at 11am instead of noon. The front is expected to make progress after midnight with the risk for TS in the SE counties much lower for the day on Friday with lower dew points moving in behind the front. 08 .LONG TERM... /Updated at 450 AM CDT Thu Mar 25 2021/ Friday night through Wednesday. Rain chances should be minimal for Friday evening but increase after midnight into the pre-dawn hours on Saturday with some thunderstorms possible in the NW with shortwave activity. Rain chances increase once again for Saturday into Sunday with the approach of another frontal system number 2. However, the upper dynamics still need to be worked out. The upper setup does not show a negatively tilted system like front 1. However, we will have warm and moist air waiting for this springtime front. While some strong storms cannot be ruled out, will hold off adding severe just yet with the weekend system. Extended guidance diverges on timing and strength of the upper low/shortwave behind the front for Mon/Tue time frame, so only going with low pops for now. A third front approaches by end of the extended by Wednesday with elevated shower and thunderstorm chances returning. 08 && .AVIATION... 00Z TAF Discussion. Showers and thunderstorms will still affect the terminals the next several hours until a cold front/trough moves through. Until then, showers and thunderstorms with gradually lowering ceilings. It appears the general trend will be for the ceilings to hold in the MVFR range at 015-030. Winds will also be gusty at times even outside convection. Low level winds will eventually lift north of the area, reducing any LLWs and wind gusts. The northern terminals will eventually become VFR by 15-18z while some clouds may hold on near TOI and MGM. As the surface boundary moves through, winds will go from south to west northwest. 75 && .FIRE WEATHER... A moist air mass with high relative humidity values will develop and continue through the weekend with multiple episodes of showers and thunderstorms. A warm front will lift northward today and produce numerous showers and a few thunderstorms. Southerly winds will increase to 10 to 15 mph with higher gusts today as a strong storm system approaches from the west. There is risk of severe thunderstorms with tornadoes this afternoon and evening. Rain chances are lower on Friday, but more showers and thunderstorms are expected for over the weekend. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 52 75 54 79 61 / 100 10 40 70 80 Anniston 57 78 59 82 63 / 100 10 40 60 60 Birmingham 55 76 60 81 64 / 100 10 50 70 80 Tuscaloosa 54 78 62 82 64 / 80 10 40 60 80 Calera 57 76 62 82 64 / 100 10 40 60 70 Auburn 63 76 64 82 64 / 80 30 20 30 20 Montgomery 64 78 65 85 67 / 90 20 20 30 30 Troy 65 80 66 85 67 / 80 40 20 20 20 && .BMX WATCHES/WARNINGS/ADVISORIES/... Wind Advisory until 10 PM CDT this evening for the following counties: Autauga...Barbour...Bibb...Blount...Bullock... Calhoun...Chambers...Cherokee...Chilton...Clay...Cleburne... Coosa...Dallas...Elmore...Etowah...Fayette...Greene...Hale... Jefferson...Lamar...Lee...Lowndes...Macon...Marengo...Marion... Montgomery...Perry...Pickens...Pike...Randolph...Russell... Shelby...St. Clair...Sumter...Talladega...Tallapoosa... Tuscaloosa...Walker...Winston. && $$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
949 PM MDT Thu Mar 25 2021 .UPDATE... Issued at 945 PM MDT Thu Mar 25 2021 Showers moving off the higher terrain over the plains are producing more wind than precipitation. QG lift will be increasing, so expect these gusty showers to continue through midnight before decreasing. New 00z models are coming in to show less moisture available tonight, as the 18z NAM was showing widespread low stratus and fog overnight into the early morning. This seemed like the outlier solution, and the 00z models are following this thinking. Will keep out the widespread low clouds and fog for tomorrow morning`s forecast. For tomorrow, PoPs seemed to be a bit too heavy handed in the late morning to early afternoon, so dialed them back just a little. Still expect isolated to scattered rain mixed with snow showers across the plains and numerous to widespread snow showers over the mountains. Can`t totally rule out a roll of thunder, as CAPE is 200-300 J/kg. Though cooler, relatively warm temperatures on the plains will allow for little to no accumulation. Over the mountains, should see 1 to 3 inches through tomorrow evening, though there will be pockets of higher amounts, possibly 4 to 6 inches, due to the convection expected. && .SHORT TERM...(This evening through Friday) Issued at 230 PM MDT Thu Mar 25 2021 A broad long wave trough will slowly approach eastern Colorado tonight and Friday. It`s currently located across the Pacific northwest and will dig south into the Four Corners by mid morning Friday. Ahead of the trough, west flow will bring in cold advection aloft across all of Colorado. However, because the trough is so broad, the flow between 700 - 500 mb is not particularly strong, thus the west upslope flow will also be not particularly strong. What this system has going for it is decent moisture and instability. PW values increase to 0.2" in the mountains and nearly 0.4" across the plains. Expect convective showers this evening across the mountains, and spreading east across portions of the plains through about 2-4 AM. No snow accumulation is expected, and it may remain in the form of rain below 6,000 ft this evening. Above 6,000 ft, all snow expected this evening into early Friday with 1-4" for the northern mountains, less along and south of I-70 with T-2" possible overnight. On Friday with the trough approaching and cold advection aloft, and mostly cloud skies across most of the area other than the far eastern plains, temperatures during the afternoon will be a few degrees cooler than today. Expect highs mostly in the 40s other than the sunnier spots across Lincoln County with low to mid 50s. The mountain valleys and foothills should be in the mid to upper 30s. QG lift from the trough is strongest across the northern half of Colorado from late morning into the late afternoon hours. This lift, combined with steep lapse rates aloft, will result in convective showers developing over the high country from the late morning through the early evening hours as the trough axis approaches. HRRR CAPE values across the mountains, foothills, and much of the plains range from 100-500 J/kg during the afternoon. Can`t rule out a rumble or two of thunder in the strongest convection later in the afternoon. The most likely scenario for convective evolution is one or two rounds of convection forming over the high county and moving east during the afternoon/evening hours. With wet bulb temps in the mid to upper 30s during the afternoon hours, expect it to fall as rain below 6500 ft. Above 6500 ft, it should fall as snow. Snow accumulations could be significant in the heavier showers with a few inches falling in 60-90 minutes with the stronger convection. Travel above 9,000 ft across the mountain passes could be impacted Friday afternoon and evening with a convective shower overhead. Total snow accumulations for the mountains and foothills will be discussed in the longer term discussion below. .LONG TERM...(Friday night through Thursday) Issued at 230 PM MDT Thu Mar 25 2021 Rain and snow showers will be winding down Friday as the system exits the region. A few snow showers could linger into Saturday morning over the mountains. Temperatures rebound Saturday with highs in the 50s over northeast Colorado. The warming trend will continue into Sunday as a ridge slides across the Central Rockies. Highs will be in the 60s across northeast Colorado. Westerly flow aloft increases Monday as an upper level trough tracks across the Great Basin and Northern Rockies. Gusty west to southwest winds will prevail. This will usher in warmer air. Highs for Monday are expected to be in the upper 60s to lower 70s across northeast Colorado. The trough progresses eastward across the Central and Northern Rockies Tuesday. The main circulation and lift will stay well north of Colorado, tracking across the U.S./Canada border. A cold front pushes through Monday evening and will bring much cooler conditions for Tuesday. A secondary circulation and upslope flow behind the cold front should bring a period of snow to the mountains, foothills, and plains on Tuesday. Temperatures look cold enough that precipitation will fall mainly as snow. Temperatures warm Wednesday after the system exits the region. However, northwest flow aloft will keep temperatures below normal. Will have low PoPs over the mountains where light orographic snow will be possible. The 12Z GFS shows a weak wave dropping southeast across the state, while other models don`t. Will have PoPs for Wednesday confined to the mountains until more models show this second wave. Ridging and warmer air should move over Colorado Thursday bringing warmer and dry conditions to the region. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 230 PM MDT Thu Mar 25 2021 Isolated to scattered showers, mostly snow, are pushing out over the airports, though these have more wind than precipitation with them. With temperatures in the low to mid 30s and already warm runways, we do not expect any accumulation this evening or overnight. Winds could be gusty under or near any of the showers, the most likely direction is WNW to NNW. All showers should end after 2-4 AM. ILS conditions are expected later this evening and should continue through most of Friday. During and after showers CIGs should be 030-050. On Friday winds should shift to NE by midday but 10 kts or less. Lower clouds will increase by mid afternoon and another round or two of showers are expected to move across the terminals late afternoon and evening. With CIG around 050, expect ILS conditions. Gusty winds up to 20-25 kts are possible in and around the showers through the evening hours. Once again, it`s most likely to be rain until after 10 PM or so, when it could mix with or change over to snow. No accumulation is expected on the runways and CIGs may drop below 030 during the showers. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Kriederman SHORT TERM...Schlatter LONG TERM...Meier AVIATION...Schlatter/Kriederman
Area Forecast Discussion
National Weather Service Buffalo NY
1019 PM EDT Thu Mar 25 2021 .SYNOPSIS... A warm front moving in tonight will generate widespread rain and possibly a few thunderstorms. A strong storm system passing close to the region will then produce strong to damaging winds Friday, along with some more showers and additional thunderstorms. Much cooler weather is expected in the wake of the system into early next week. && .NEAR TERM /THROUGH FRIDAY/... A deepening storm tracking across the Mid Western states overnight will push a warm front into our region. Radar showers an initial line of showers with a segment of this front moving into western New York Lake this evening. This area of showers will continue to expand, as widespread rain develops across the area overnight. There should be enough elevated instability to maintain the mention of a few thunderstorms. Rainfall generally up to a half inch although locally higher amounts will be possible in any convection. A high wind event still looks to be on track for Friday with STRONG TO DAMAGING winds likely. 12z model guidance still supporting a storm track just off to our west with a favorable 925 mb jet positioning of 50-60 knots focused right across western New York. Elected to limit High Wind Warning to western areas where best low level jet is focused and best 3-hour pressure couplet is forecast. Latest HRRR guidance supports this warning, but suggests a fairly narrow time window with the strongest winds lasting 2-3 hours. The burst of strongest winds (about 60 mph) will reach Buffalo around 11 a.m. and Rochester around 1 p.m. Along with the strong winds, showers will continue and possibly thunderstorms. This will especially be the case across the Eastern Lake Ontario region where there will be a chance for more robust convection. SPC has placed this region in a marginal risk for severe weather on Friday. Temperatures Friday will peak early in the day then fall back from west to east during the afternoon as the strong winds usher in notably cooler air. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... High pressure will move into the eastern Great Lakes Friday night through Saturday. The pressure gradient between exiting low pressure off the coast of Newfoundland and approaching high pressure from the west will keep winds on the gustier side for the first half of Friday night, before quickly diminishing from west to east. Northwest flow and lingering wraparound moisture Friday night will allow a changeover to snow across the North Country. This leaves some chances for a quick dusting of snow on the Tug Hill late Friday night. Mid levels quickly dry out in the second half of the night as high pressure builds into the area by Saturday morning. Overnight lows will be in the mid 30s, with some upper 20s possible for the Tug Hill. Cold air advection will result in 850mb temperatures falling to -2C. While a bit cooler than the recent warm stretch, temperatures will remain mild on Saturday with highs in the mid to upper 50s across western NY and the mid to upper 40s east of Lake Ontario. Dry conditions expected on Saturday as high pressure remains in control. Weak warm air advection Saturday night into Sunday ahead of the next system will help keep temperatures steady through Saturday night, with overnight lows only dipping into the mid 40s, mid to upper 30s east of Lake Ontario. More active weather returns as a deepening upper level trough moves across the Great Lakes region late Saturday night into Sunday. A rapidly intensifying 250MB jet on the east side of the trough will enhance cyclogenesis as low pressure moves to the northwest of the region. A strong cold front will track across the region during the day Sunday, with deep moisture and large scale ascent resulting in widespread rain across the eastern Great Lakes. Strong cold air advection behind the front will drive Canadian air into the region, allowing rain to change over to light snow showers late Sunday night into Monday. 850mb temperatures will likely drop low enough to generate some lake enhancement late Sunday night and into Monday as well. Highs on Sunday will peak early in the day with upper 40s and low 50s before quickly falling behind the front. Lows Sunday night will drop into the mid 20s to low 30s. && .LONG TERM /MONDAY THROUGH THURSDAY/... Drier air will quickly build in to start the period as high pressure located just to the west moves eastward over the lower Great Lakes. Other than a leftover stray light rain or wet snow shower, expect a mainly dry, but cool and breezy start to the new work week. High pressure will remain in control of our weather through at least late Tuesday keeping dry conditions intact, all while a milder airmass quickly moves back across the region owed to a southerly return flow as aforementioned surface high pressure moves off the southern New England coast and upper ridge crests over the Northeast on Tuesday. As far as how this impacts temperatures, daytime highs ranging from mainly in the mid 30s to mid 40s on Monday will climb substantially for Tuesday with highs ranging mainly from the lower 50s to lower 60s. Next chance for any precip returns Tuesday night as the upper ridge axis moves east over New England, while an embedded shortwave rides northeast up the back side of the ridge. Meanwhile its` surface reflection in the form of a warm front will move toward our area from the Ohio Valley. The combination of these two features may bring a few scattered light showers Tuesday night. Decent forcing but a lack of overall moisture will limit overall shower coverage. Warm front moves north of the area later Tuesday night, with a brief period of mainly dry conditions possible Wednesday morning. This will place our region firmly in the warm sector for Wednesday, with most areas climbing at least into the 60s. A strong cold front is then poised to plow across the region sometime late Wednesday and Wednesday night bringing the next best chance for some widespread beneficial rainfall. Mother Nature may be playing the April Fool`s joke this year as a much colder airmass pours across the eastern third of the CONUS in the wake of the cold frontal passage, making for a chilly and raw start to the month of April with the possibility of a mix of rain and snow showers. Highs Thursday may not get out of the 30s across the higher terrain, with mainly lower 40s elsewhere. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... A warm front lifting north across the region will lead to lowering cigs tonight. Cigs will lower to MVFR and possibly IFR across the lake plains due to a northeasterly flow just before the front moves through. After this, expect brief improvement as winds shift to the SSW with downsloping helping to raise cigs a bit. During this time showers will spread from south to north this evening, followed by steadier rain late tonight. Low pressure will pass just to the north on Friday, with winds increasing significantly with its passage. Strongest winds will be 15Z to 21Z with peak gusts around 50 kts at KBUF/KIAG/KROC. Otherwise, some showers and possibly a thunderstorm with mainly MVFR cigs and patchy IFR possible northeast of the lakes and across higher terrain. Outlook... Friday night and Saturday...Mainly VFR. Sunday...VFR/MVFR. Showers likely. Monday and Tuesday...Mainly VFR. && .MARINE... A deepening storm system will track across the mid western states tonight. This will encourage winds to freshen from the east- southeast during the course of the night. The strong storm system will then pass through the Lower Great Lakes region on Friday with winds intensifying to gale force by mid morning to early afternoon. West to southwest gales during the afternoon will then drop off late in the day and Friday night. Gale warnings are in effect for all of the Lower Great Lakes as well as for the entire length of the Niagara River. Small Craft headlines were issued for the St. Lawrence River to Ogdensburg, with weaker winds north of Ogdensburg since the surface low is expected to track near that area. Winds will continue to weaken on Saturday, as high pressure will pass over the region. && .HYDROLOGY... The combination of about an inch of rain along with snow melt from warm weather will cause rises on Black River and its tributaries in the Friday night through Sunday night timeframe. Rainfall amounts is the main forecast challenge with high confidence in warm weather and a steady run-off from the snow pack which is still in place across higher terrain. Latest modeling places around an inch of rain in the basin from the Friday system, producing action level rises. Latest GEFS and NAEFS ensembles suggest that there`s at least some risk for Watertown to reach flood stage but this probably would be following a second system on Sunday. Probabilities of flooding at Boonville and McKeever are non-zero but very low. The HEFS which accounts for some model QPF bias shows a lower risk for flooding, and this seems the most likely scenario and the one the NERFC is forecasting. There is still a small risk of flooding if basin average rainfall amounts from the two systems reaches around 2 inches. For now, will maintain a mention in the HWO for the Black River basin with confidence well below 50 percent, the threshold for issuing a Flood Watch. && .TIDES/COASTAL FLOODING... Higher than normal water levels on Lake Erie combined with a period of gale force southwest winds Friday will result in the sharply rising lake levels on the east end of the lake and some lakeshore flooding. At this time, levels are expected to peak between 8 and 9 ft at the Buffalo NOS gauge. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...High Wind Warning from 8 AM to 4 PM EDT Friday for NYZ001>003- 010>012-019-020-085. Lakeshore Flood Warning from 8 AM to 4 PM EDT Friday for NYZ010-019-085. Wind Advisory from 10 AM to 8 PM EDT Friday for NYZ004>007-013- 014-021. MARINE...Gale Warning from 11 AM to 6 PM EDT Friday for LEZ020. Gale Warning from 8 AM to 6 PM EDT Friday for LEZ040-041. Gale Warning from 11 AM to 6 PM EDT Friday for LOZ030- 042-062. Gale Warning from 2 PM to 8 PM EDT Friday for LOZ043>045- 063>065. Small Craft Advisory from 2 PM to 8 PM EDT Friday for SLZ022. && $$ SYNOPSIS...TMA NEAR TERM...Apffel/TMA SHORT TERM...PP LONG TERM...JM AVIATION...Apffel/RSH/TMA MARINE...Apffel/RSH/TMA HYDROLOGY...Apffel/RSH TIDES/COASTAL FLOODING...RSH/TMA/Apffel
Area Forecast Discussion
National Weather Service Peachtree City GA
1033 PM EDT Thu Mar 25 2021 .UPDATE... Expanded Tornado Watch into far NW counties given some cell redevelopment trends in eastern AL and collab with SPC. Baker && .PREV DISCUSSION... /Issued 1013 PM EDT Thu Mar 25 2021/ PREV DISCUSSION... /Issued 846 PM EDT Thu Mar 25 2021/ UPDATE... Training cells and heavy rain across far north GA has resulted in 1-3 inches and locally higher near 5 inches this evening. Keeping Flash Flood Watch going through overnight with additional 1-3 inches possible along with ongoing warnings in effect. Still monitoring for severe/tor potential given ample high shear and decent instability axis advecting in from west and south ahead of main front. Tornado Watch in effect through 2 AM across northwest half of CWA. Made slight pop adjustments and added severe mention in weather grids, otherwise previous fcst and expected storm threats continue with little change made. Baker PREV DISCUSSION... /Issued 810 PM EDT Thu Mar 25 2021/ UPDATE... 00z Aviation update below. Baker PREV DISCUSSION... /Issued 348 PM EDT Thu Mar 25 2021/ SHORT TERM /Tonight through Friday Night/... Widespread showers and a few thunderstorms are underway across north Georgia this afternoon, mainly along and north of a line from Cedartown to Roswell to Flowery Branch, where a warm front is situated. This warm front is extending out from a surface low located over the ArkLaMiss, placing the CWA within a warm, moist, unstable environment this afternoon. A Tornado Watch is in effect for northwestern GA until 9 PM EDT, where 0-1 km SRH values are an impressive 350-450 m^2/s^2. In addition to the tornado threat, this area will be ripe for supercells capable of large hail and damaging wind gusts through the afternoon and evening. The threat for severe storms will continue overnight into early Friday morning as the surface low (at that point located over the Great Lakes region) drives a cold front across the CWA from west to east. CAMs generally show a broken line of storms entering northwestern GA around 02z-04z, pushing through metro Atlanta between 05z-10z. The threat for severe storms will continue to be maximized across northern and western GA, where several severe weather parameters are forecast to come together. At the upper levels, a strong shortwave trough will lift northeast across the Great Lakes region overnight, maintaining broad ascent across the CWA (though the strongest upper dynamics will remain well to our northwest). Still, some 65-75 kts of bulk shear will be in place over northern and western GA overnight. In addition, 0-3 km SRH values of 350-450+ m^2/s^2 and 0-1 km SRH values of 250-350+ m^2/s^2 will maintain a threat for organized, rotating storms with tornadic potential. RAP and NAM significant tornado parameter values across this portion of the CWA are 3 to 6, so the concern for isolated tornadoes (some strong and/or long-tracked possible) is certainly there. Even with the nighttime arrival of the storms, MUCAPE will be 1000-1500 J/kg and forecast soundings suggest mid- level lapse rates around 7.5-8.0 C/km, so large hail will also be a threat with the storms overnight. The line of storms will continue progressing eastward tomorrow morning into the afternoon across central and eastern GA, but severe storm parameters look to be much more marginal. That said, decent shear and instability could make for a few strong to severe storms. Martin && .LONG TERM /Saturday through Thursday/... At the start the forecast period on Saturday, the lingering frontal boundary will begin to quickly lift back north across north Georgia as a warm front. The best chance for rainfall will thus be across the northern third or so of the area on Saturday. Some embedded thunderstorm activity will be possible Saturday initially associated with elevated instability north of the warm front. Rainfall coverage will diminish farther south of the cold front where temperatures will soar well into the 80s in central Georgia. On Sunday, shower and thunderstorm coverage will increase appreciably as the cold front pushes southeastward into the CWA. The threat for strong/severe thunderstorms appears considerably lower with this system at this time as dynamics will be much more limited, though a few stronger storms can`t be ruled out. The primary risk from Saturday into Sunday will be additional heavy rainfall and flooding concerns across far north Georgia. These areas will have already seen several inches of rain prior to the weekend event, which could add another 1-2 inches of rainfall. Guidance diverges by next week with respect to the evolution of the upper low over the Southwest. The GFS maintains a southern track shortwave along the Gulf Coast while the ECMWF lifts the low northeastward into the Plains. At this point, kept slight chance to low end chance PoPs on Tuesday given uncertainty. By midweek, the next surface front approaches bringing increasing rain chances areawide. RW && .AVIATION... 00Z Update... TSRA could be in several rounds with initial pushing in from east AL (tempo TS with VRB gusts near KATL for 01-05z period), then could have redevelopment closer to front for the early morning hours so will monitor for any tempo extension. Looks like MVFR cigs overnight as well then improving from the north after 12/15z. Southern sites could have more lingering showers or again some storms Friday afternoon with stalling front. Winds initially 10-12 kts with some low end gusts possible out of SSE to SSW (favoring SSW for KATL), then more west to NW shift 6-7 kts behind front after 12z. //ATL Confidence...00Z Update... Medium on all elements. Baker && .PRELIMINARY POINT TEMPS/POPS... Athens 63 78 57 80 / 70 40 20 50 Atlanta 61 75 60 81 / 70 30 30 40 Blairsville 55 73 49 71 / 100 20 30 80 Cartersville 58 75 55 80 / 100 20 40 60 Columbus 66 77 64 85 / 60 50 20 10 Gainesville 60 75 55 75 / 90 30 30 70 Macon 68 77 63 86 / 50 50 20 20 Rome 57 76 53 79 / 100 10 40 70 Peachtree City 62 75 59 83 / 70 40 20 30 Vidalia 68 84 66 88 / 10 30 5 10 && .FFC WATCHES/WARNINGS/ADVISORIES... Tornado Watch until 2 AM EDT Friday for the following zones: Banks...Barrow...Bartow...Carroll...Catoosa...Chattooga... Cherokee...Clarke...Clayton...Cobb...Coweta...Dade...Dawson... DeKalb...Douglas...Fannin...Fayette...Floyd...Forsyth...Gilmer... Gordon...Gwinnett...Hall...Haralson...Harris...Heard...Henry... Jackson...Lumpkin...Madison...Meriwether...Murray...Newton... North Fulton...Oconee...Paulding...Pickens...Pike...Polk... Rockdale...South Fulton...Spalding...Troup...Union...Walker... Walton...White...Whitfield. Flash Flood Watch until 8 AM EDT Friday for the following zones: Bartow...Catoosa...Chattooga...Cherokee...Dade...Dawson... Fannin...Floyd...Gilmer...Gordon...Lumpkin...Murray...Pickens... Polk...Towns...Union...Walker...White...Whitfield. && $$ SHORT TERM...Martin/Baker LONG TERM....RW AVIATION...Baker
National Weather Service Hastings NE
630 PM CDT Thu Mar 25 2021 .DISCUSSION...(This evening through Thursday) Issued at 319 PM CDT Thu Mar 25 2021 Lingering stratus and redeveloping cumulus has kept skies partly to mostly cloudy this afternoon. As a result, highs may struggle to reach 50 degrees in some spots, especially in eastern portions of the area. This will clear out this evening and overnight, allowing temperatures to dip into the low to mid 30s. The HRRR shows some fog over eastern portions of the area early Friday morning as moisture returns ahead of the next system. Confidence in this remains low, so this was kept out of the forecast for now. Southeast winds increase on Friday as an upper shortwave and associated surface low move out into western Kansas. A few rain showers are possible through the morning, but rain amounts will remain pretty light. By afternoon, a warm front should set up just south of the Kansas/Nebraska state line, with moisture and instability increasing near and south of it. By late afternoon, the HREF mean shows MUCAPE between 500-1000J/kg for areas south of I-80. This is coincident with effective shear of 35-40kts. With the relatively limited CAPE, updrafts will not be overly intense, but the abundant shear may allow the strongest updrafts to organize into isolated low-topped supercells with the primary threat being marginally severe hail/wind. Models are in general agreement that the highest coverage of storms will be in southeastern portions of the area, but an isolated storm or two cannot be ruled out across the entire area. Activity will shift east of the area after midnight as the upper trough axis moves through. Behind this system, a deeper upper trough will push through, ushering in gusty northwest winds on Saturday. Then a warming trend will will take hold Sunday into early next week as upper level ridging builds overhead. High temperatures in the 70s appear likely on Monday. This warmth and increasing south winds may also lead to some near-critical fire danger Monday. A cold front then moves through Monday night into Tuesday, leading to a strong northwest winds and noticeable cooldown on Tuesday. Some light rain is also possible as a deep upper trough passes through Tuesday night into Wednesday morning. This will keep temperatures near to below normal as we start the month of April. Beyond that, there is good agreement in medium range ensembles for a return to above-normal temperatures for Easter weekend. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 619 PM CDT Thu Mar 25 2021 Quiet weather with VFR conditions are expected this evening into the overnight hours...though confidence suffers a bit for KGRI with the potential for it to be on the western edge of some fog development. Not all models/guidance agree with it occurring, so kept visibility at 6SM at this point. As we get into Friday, an upper level wave moving into the region will bring the potential for some shower mid-morning into part of the afternoon, but uncertainty remains with just how much activity there actually is, so have a VCSH mention at both terminals. There will be increasing chances for more activity (and thunderstorms) in the latter few hours of this period, but at this point the main focus looks to be to the south of the terminals. Winds through the period are expected to remain generally southeasterly, can`t rule out a few gusts near 20 MPH tomorrow. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Mangels AVIATION...ADP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1036 PM EDT Thu Mar 25 2021 .SYNOPSIS... A vigorous cold front is expected to move through the area later tonight and into Friday and could produce isolated strong to severe convection along with significant rainfall. The active pattern continues this weekend as another cold front slides through the area on Sunday bringing another round of showers and thunderstorms. && .NEAR TERM /THROUGH FRIDAY/... As of 1025 PM Thursday: The cold front was pushing through central TN and AL with more discrete convection continuing to fire ahead of it. A couple of these cells tried and failed to hold together as they pressed into far northeast GA largely due to them running into the more stable environment. The latest SPC HRRR shows that later discrete cell should hold together into the western Carolina`s and especially northeast GA as a tongue of 500-1000 CAPE noses into the area from the south thanks to increasing southerly flow ahead of the front. Feel this could be a bit overdone but with impressive shear and helicity values should be enough for at least a few super cell thunderstorms capable of damaging winds, an isolated tornado, and perhaps large hail. This threat should be mainly west of I-26 and between roughly midnight and 4 am. Flood concerns will continue especially for the southwest mountains. Rainfall totals have already exceeded 5-6 inches at some higher elevations with an additional 1-2 inches possible before all is said and done. The Flash Flood Watch has been updated accordingly. As of 830 PM Thursday: The latest surface analysis shows what appears to be a weak insitu-wedging roughly along and north of I-85 this evening that developed from the steady rainfall from earlier today. This is indicated by weak high pressure nosing southwest from the NC Piedmont towards northern GA. This will limit surface based CAPE and instability overall for this area. This combined with gradually diminishing upper support as the parent low moves northeast into the Great Lakes and loss of daytime heating should limit the coverage of severe thunderstorms compared to neighbors to our west. That being said SPC recently issued a Tornado Watch for much of northern GA good through 2 am, just to our west, so we will be watching the developing situation closely. On that note, high values of shear/helicity will continue along and ahead of the cold front, so it probably won`t take much instability to maintain strong to severe thunderstorms (a high shear/low cape environment). Steady rain with embedded heavy rain will likely continue especially near the southwest mountains overnight. So we will likely see additional flooding during this time with the current Flash Flood Watch seemingly well placed for the time being. Otherwise, we remain under a weak WAA regime and influence of a subtropical ridge off the SE Coast. This ridge is downstream of an expansive trough, within which a potent shortwave will move today, driving development of a low pressure system over the lower MS Valley. A significant severe outbreak is expected over portions of the TN, MS, and AL. Fairly brisk southerly flow has already initiated convection over the high terrain. The depth and strength of moisture advection will be impressive, leading to PWATs peaking near +3 SD, and IVT parameter values that are also anomalously large. Deep layer hodographs will already be long and curving, but midlevel lapse rates are not the greatest; the limited instability will keep our severe threat comparatively small during the day, with convective layers too shallow to realize all the shear. This does somewhat limit our heavy rain threat as well, though there will be widespread coverage and potential for multiple rounds thru tonight. WPC Day 1 ERO includes most of our SW mtns in a Moderate Risk, partly because of the aforementioned anomalies and high probabilities for significant rain rates from the HREF. We are hoisting a Flash Flood Watch from 18z today to 12z Fri. The same southerly flow will lead to rather gusty winds, and higher elevations of the mtns will be exposed to near Wind Advisory-level conditions. LLJ is expected to precede the cold front into our area in the early evening, again enhancing precip generation along the srn end of the Appalachians; a narrow tongue of sfc based instability will linger until the front itself enters in the late evening. A convective line, likely with some embedded rotation will support vague supercell structure. The dynamic lift provided by the shortwave will mostly miss our area to the NW as the wave tracks north of the OH River; this coupled with the unfavorable timing, and diminishing instability, should begin to impact the convection particularly as it crosses the mountains. Nevertheless, a narrow line of strong showers with a few embedded tstms could progress across the area overnight. Prog soundings reveal that the line will encounter poor low to midlevel lapse rates, and this would limit sfc based updrafts and thus tornado risk. The SPC slight risk extending only into the mtns looks well-placed and even extended slightly further east. Recent short-term consensus PoPs as well as hourly NBM seem to be keying better on the shadowing effect of the mtns, and timing/chances have been revised thru tonight in new fcst grids. The frontal boundary should push out of the region by 18z Friday as sfc high builds in to the NW and we enter a post-frontal environment by the very end of the forecast period. Drier weather will prevail, with highs in the low 80s in most locations outside the mountains and 70s in the higher elevations. One factor that can play a role is how fast the cold front exits the region and allows for the clouds to scour out. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 145 PM EDT Thursday: the short term picks up at 00Z Saturday, with a shortwave trough rounding the broader ridge sitting over the east coast. By this time, forcing from the trough will largely be tapering off to the north of our CWA, and a brief bout of dry weather is in store for Friday night. Renewed southwesterly flow over the Tennessee Valley will pump Gulf moisture into the lower troposphere through the day Saturday, working with weak mid-level forcing to produce scattered afternoon showers across TN, spreading into the Blue Ridge Mountains and western SC Upstate by late Saturday afternoon. The developing surface low skirts its way northeast along the Appalachians and drags a cold front across our area early Sunday afternoon. Ample WAA ahead of this front paired with decent solar insolation should prime the environment for convection, with the Piedmont and Upstate seeing SBCAPE values in the 500-1000 J/kg range and a 40-50kt LLJ riding out ahead of the frontal boundary. Given the timing of the frontal passage in the early afternoon, this is a pattern to keep an eye on over the next day or two. Some precip may still be falling for at least the eastern part of our CWA by the end of the short term at 00Z Monday, as the front tapers off to the east. Temps are on track to stay several degrees above normal on Saturday and Sunday, before dropping back to near-normal Sunday night in the wake of the cold front. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 200 PM EDT Thursday: by Sunday night, good mid-level forcing associated with the latest trough is exiting the region to the east, and precip drops off overnight behind the departing cold front. We then enter a weak upper ridging regime as high pressure builds in at the surface. So, Monday should be dominated by clear, dry weather as the frontal boundary stalls well south of us. Meanwhile, the GFS and ECMWF depict a closed upper low meandering out of the Southern Plains and causing coastal cyclogenesis along the stagnant frontal boundary. The resulting surface low tracks from the Gulf Coast out to the NC/SC coastline. It looks to only graze our CWA at this point, yielding chance PoPs on Tuesday afternoon and overnight. On Thursday, yet another surface low pushes into the region from the west, bringing another bout of rainfall to the region to cap out the week. Temperatures on Monday and Tuesday look to be a couple degrees below normal, before southerly WAA brings them back to near-normal later in the week. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... At KCLT and elsewhere: Below normal confidence in 00Z TAFs due to uncertainty in timing and strength of convective line to move through the area from west to east between roughly 05Z and 15Z. Steady rain with isolated TSRA is expected ahead of this feature with IFR and lower cigs/vsbys likely in heavier shra/tsra. Front may stall south of TAF sites into Friday with little if any impact to terminals. Outlook: Another system may bring showers Saturday with thunderstorms possible by Sunday. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 86% High 97% High 81% High 100% KGSP Med 77% Med 61% High 100% High 100% KAVL Med 73% Med 60% High 100% High 100% KHKY Med 67% Med 72% High 100% High 100% KGMU Med 79% Med 72% High 100% High 100% KAND High 87% High 86% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...Flash Flood Watch until 8 AM EDT Friday for GAZ010. NC...Flash Flood Watch until 8 AM EDT Friday for NCZ051-052-058-059- 062>064. SC...None. && $$ SYNOPSIS...MPR NEAR TERM...CAC/Munroe SHORT TERM...MPR LONG TERM...MPR AVIATION...Munroe
Area Forecast Discussion
National Weather Service Indianapolis IN
1144 PM EDT Thu Mar 25 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 950 PM EDT Thu Mar 25 2021 Sent update to the High Wind Warning and Wind Advisory. Some concerns per latest HRRR model, wind gusts away from convection may not be quite as high as anticipated. That said, center of low pressure will deepen tonight and lift northeast across west central and northern Indiana. This will result in low level wind acceleration and jetlet lifting northeast across the forecast area. So, will keep the headlines going. With dry slot lifting northeast across southwestern parts of the forecasts area, lowering PoPs look on track. Will be dropping Knox and Daviess from the Tornado Watch as well with support from SPC. && .Short Term...(This Afternoon through Friday night) Issued at 233 PM EDT Thu Mar 25 2021 ...SEVERE STORMS POSSIBLE THIS EVENING... ...HIGH WIND EVENT EXPECTED TONIGHT... This Afternoon and Tonight... Initial area of warm advection precipitation currently moving through the area is expected to lift off to the northeast by the late afternoon hours. Little to no surface or elevated instability exists over the area at this time, although short term model data suggest decent elevated instability for this time of year may begin advecting in from the south towards evening, courtesy of steeper mid level lapse rates in the wake of this afternoon`s rainfall. Short term models suggest another area of significant lift, associated with the upper low/vorticity lobe and surface cold front/occlusion moving out of the Missouri and Arkansas area, will approach the southwest zones around 260000Z-260100Z. As a result, expecting more widespread showers and thunderstorms to begin developing by that time. Deep layer shear and helicity values continue to look very high ahead of the front this evening, especially over about the southeast two thirds of the forecast area. This coupled with the elevated instability should support rotating storms, both along and ahead of the front, but limited surface based instability may help to keep any circulations elevated. Will have to closely monitor instability trends this evening. The front is expected to pass off to the northeast by 260500Z or so, which should end any convective severe threat. Some wrap around rainfall, associated with the upper low, may move through mainly the northern zones during the early morning hours of Friday, so will keep PoPs a little higher in those areas late tonight. Models continue to suggest near dry adiabatic lapse rates up to about 900mb in the immediate wake of the frontal passage, along with a 50-60 kt low level jet wrapping around the back side of the low. This scenario supports the potential for winds in excess of 50 kts to mix down for a period in the post frontal zone late tonight. Based on above, decided to expand the warning a bit farther west, and especially southeast, where it appears the best momentum transfer may occur, given the expected surface low track. Friday and Friday night... Expecting winds to diminish fairly rapidly Friday morning, as the surface and upper systems move away quickly. Otherwise, this period looks rather quiet, with surface high pressure moving into the local area by Friday afternoon and evening. && .Long Term...(Saturday through Thursday) Issued at 233 PM EDT Thu Mar 25 2021 On Saturday and Saturday Night... The GFS and ECMWF shows a deep trough aloft moving through the Plains states with SW flow in place across Indiana. Good forcing is seen across Indiana ahead of the approaching upper trough axis. Meanwhile at the surface a quick moving area of low pressure is expected to push from Iowa to the Great Lakes...dragging a cold front across Indiana on Saturday night. These features will have ample moisture and forcing to work with...thus will include higher pops at that time. Sunday through Tuesday... Dry weather will be expected as the GFS and ECMWF show broad ridging in place aloft across the plains with some lee side subsidence over the Ohio Valley. This results in a broad high pressure system slowly pushing across our region through the early part of the work week. Thus will trend toward partly cloudy days and night and not veer far from the NBM on temps. Tuesday Night Through Wednesday Night... Another round of precip looks possible for the middle of the next work week. The GFS and ECMWF once again show the development of a broad upper trough settling across the plains states. This once again results in southwest flow in place across Indiana and the Ohio valley...allowing ample moisture and embedded short waves within the flow to provide forcing. Lower levels depict a cold front approaching Indiana and pushing across the state on Wednesday Night. Thus have included higher pops in this window. With expected rain will trend lows warmer and high cooler than NBM. Thursday... Dry weather should return at this time as high pressure is expected to build across the area from the plains in the wake of the front. Once again strong Ridging builds across the northern plains...allowing subsidence to build across the Great Lakes and Ohio Valley. && .Aviation...(06Z TAF Issuance) Issued at 1144 PM EDT Thu Mar 25 2021 IMPACTS: - Gusts over 35 knots and up to 50 knots through 10z-13z. - Wind direction SW and W. - MVFR and occasional IFR ceilings through 21z or so and then VFR. - Showers ending 08z-10z. DISCUSSION: Strong low pressure system will move lift out northeast from northern Indiana to the eastern Great Lakes ovenight. Windy conditons overnight and dropping off sharply after 12z as the system moves away. The showers will be ending overnight as well from southwest to northeast. && .IND WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 9 AM EDT Friday for INZ021-029>031- 036>042-045>049-053>057-062>065-070>072. Wind Advisory until 9 AM EDT Friday for INZ028-035-043-044-051- 052-060-061-067>069. && $$ Update...MK Short Term...JAS Long Term...Puma Aviation...MK
National Weather Service Jackson KY
1135 PM EDT Thu Mar 25 2021 .UPDATE... Issued at 1135 PM EDT THU MAR 25 2021 The forecast package was updated to include the tornado watch for the southwest parts of the CWA through 2 am. The wind shear aloft remains sky high some instability has been advected into that area where the individual cells are now capable of being organized. A broken lines of strong to severe storms is preceding the cold front now pushing through central Kentucky. QLCS conditions and the environment support the tornado threat for the watch area until the synoptic boundary races east into the more stable and worked over air over further east in the JKL CWA. Added and adjusted the severe threat in the grids as well as including the latest obs and trends for the T/Td grids. These updates have been sent to the NDFD and web servers along with the issuance of the WCN, HWO, ZFP, and SAF. UPDATE Issued at 820 PM EDT THU MAR 25 2021 23z sfc analysis shows a fairly deep area of low pressure moving through western Kentucky with its warm front now north of most of the JKL CWA putting the area in the warm sector. The latest batch of pcpn associated with the warm front is lifting out but not before stabilizing the air mass, if only briefly. The strong wind shear remains in place aloft and will be available to help sustain any stronger storms that manage to redevelop, but instability will need to mostly advect in ahead of the system`s cold front to give us a good shot at seeing some severe weather. We will be under the gun until the front moves through after midnight, though, so near term model and radar trends will be key for any potential warnings or statements this evening and early overnight. The updraft helicity swaths from the HRRR does suggest a window from 10 pm to just past midnight with that front when the storms could be strongest moving through the CWA. Otherwise, gradient synoptic winds will be strong enough to break off tree limbs or blow some poorly anchored ones down through the overnight - with the Wind Advisory addressing this threat even outside of stronger storms. Otherwise, temperatures are generally in the low to mid 60s while dewpoints range from the mid 50s northeast to the low 60s west under cloudy skies. Winds are still south to southeast at 10 to 20 mph with gusts pushing 30 mph for most. Have updated the forecast to time the best storm chances through the next 6 hours or so and also to add in the latest obs and trends. These updates have been sent to the NDFD and web servers with an update to the ZFP to be issued shortly. && .SHORT TERM...(This evening through Friday night) Issued at 510 PM EDT THU MAR 25 2021 Late this afternoon, a shortwave trough was approaching the mid MS and Lower OH valley region with a gradually deepening sfc low approaching the confluence of the OH and MS Rivers at this time. The shortwave trough will track across the OH Valley this evening and into the overnight reaching the Great Lakes late tonight before moving across the northeast and into the Canadian maritimes Friday to Friday night. The sfc low will continue to deepen and take this same path, sending a cold front east across the Commonwealth through this evening into the early portions of the overnight hours. Height rises and a mid and upper level ridge will shift across East KY and the Appalachian region for Friday into Friday night. Meanwhile, sfc high pressure will shift across the area, settling across the central Appalachians on Friday night. Locally winds have been southeast to south southeast behind the initial area of showers that affected East KY this morning into the afternoon. The early day showers and clouds have limited heating. Dewpoints are currently in the upper 50s to low 60s across the region, although some low to mid 50s are occurring nearer to the VA border where the downslope affects area bit stronger at present. Dewpoints are higher in the low to mid 60s across portions of east TN into middle TN and western and central KY. Convection has been developing over middle TN and portions of East TN over the past couple of hours with the strongest storms at present in the Nashville TN vicinity and nearing the Cookeville TN area. As the sfc low tracks northwest of the area and a warm front lifts toward the southwestern portions of the area this evening, the convection now south of the area will move into the Lake Cumberland/Cumberland Valley area, likely before sunset. A discrete cell or two is is possible with this activity, but instability is limited with north and northeastward extent. Some increase in instability is expected in advance of the approaching cold front and some filtered sunshine has been occurring across the far south and southwest. The severe threat across the region still appears to be somewhat conditional on instability as shear will not be an issue. After any initial activity before sunset, a line or broken line along or in advance of the cold front should affect the area late this evening and reach the WV border an hour or two after midnight. With such strong wind fields aloft, 850 mb winds likely in the 60 to 70KT range if not briefly higher, this activity could translate higher momentum to the surface. Wind fields likely diminish toward dawn on Friday. The primary threat with any pre sunset activity or activity near or along the cold front still appears to be strong wind gusts. Shear is substantial so in the area where instability is expected to be greatest west and south of eastern KY, chances for tornados will be highest. The threat does appear to extend into locations from near Mount Vernon to Middlesboro and west where limited instability is expected to extend north. Thus, a couple of isolated tornados cannot be ruled out. Also, outside of any thunderstorm activity, some of the higher momentum should be mixed to the sfc at times with gusts of 35 to 45 mph possible. These gusts could be locally higher across the west and north as well as the highest elevations along the VA border. Thus a Wind Advisory has been issued through 8 AM on Friday as well. The Friday into Friday night period will be dry with high pressure dominating. Eastern valleys should drop off well into the 40s on Friday night. .LONG TERM...(Saturday through Thursday) Issued at 350 PM EDT THU MAR 25 2021 The extended period continues to look active, with multiple weather systems forecast to move through the region this weekend and parts of next week. The first batch of active weather is slated to occur Saturday through Sunday, as a large trough of low pressure aloft makes its way across the northern CONUS. A southern stream system will combine its energy with a northern stream low, both of which are forecast to move across the Great Lakes and lower Tennessee valley regions Saturday through Sunday. The latest model data is suggesting that there will be enough lift, moisture, and instability to not only produce thunderstorms Saturday and Saturday evening, but that enough ingredients may be in place to create a few strong to marginally severe storms. That being said, a couple of storms Saturday afternoon and early Saturday evening could produce strong gusty winds. As the surface cold front with the northern stream system moves through the area Saturday night and Sunday, we will likely see widespread rain showers continue around eastern Kentucky. Any storms should come to an end by late Saturday evening. The last bit of rain should move out of the area early Sunday evening. Clear skies and light winds, along with ample surface moisture, will set the stage for frost formation late Sunday night into early Monday morning, especially in our deeper and normally colder valley locations. High pressure will keep the weather nice otherwise through the end of the day on Monday. Another area of low pressure may bring a few rain showers to eastern Kentucky late Monday night and Tuesday. Another weather system on the heels of the Tuesday system is progged to move through the region Wednesday evening through Thursday. The front associated with the third system may spark a few thunderstorms late Wednesday afternoon and early Wednesday evening. This third batch of rain will likely persist through Thursday. Temperatures in the extended should generally be above normal, with daily highs most days topping out in the upper 60s to low 70s. Nightly lows, with the exception of Sunday night, should be above normal as well. Lows by Monday morning may fall into the low to mid 30s, coldest in the valleys, which will set the stage for frost formation. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 745 PM EDT THU MAR 25 2021 Lead area of pcpn associated with the approaching system is lifting through eastern Kentucky ATTM with mainly just some showers and weak thunderstorms. Winds are roaring aloft and some these have been able to come to the sfc with these showers as evident by the 35kt gust at JKL this past hour. Later, look for a line or broken line of convection moving into the aviation forecast area along or just ahead of a cold front generally during the 02 to 05z timeframe. Some ongoing MVFR restrictions in departing showers should improve to VFR for a couple of hours. However, additional restrictions back into the MVFR or even IFR range are possible, at least briefly within convection that occurs after 02z. Some of the storms could be strong to severe with wind gusts in excess of 50 kts possible locally. Chances for severe thunderstorms are greatest along and west of I-75 including the KSME and KLOZ sites. Otherwise, winds will increase through 03z out of the south to southwest into the 10 to 20 kts range with gusts as high as 40 kts possible. These strong winds will gradually diminish from 10 to 15z as the front departs. Likewise, look for MVFR CIGS to start to lift back to VFR in the afternoon on Friday - generally from west to east. && .JKL WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 8 AM EDT Friday for KYZ044-050>052-058>060- 068-069-079-080-083>088-104-106>120. && $$ UPDATE...GREIF SHORT TERM...JP LONG TERM...AR AVIATION...JP/GREIF
Area Forecast Discussion
National Weather Service Melbourne FL
927 PM EDT Thu Mar 25 2021 .DISCUSSION... Mild and humid conditions will continue, with temps only falling as low as the mid to upper 60s late tonight (potentially not falling below the 70 degree mark for coastal locations south of the Cape) as a light southerly flow persists across the region. Despite the persistence of hi-res model guidance wanting to generate a few showers from the sea breeze collision over the interior this evening, subsidence from ridge aloft and overall dry airmass will keep rain chances out of the forecast. Some fog development may be possible late tonight toward daybreak Friday, but HRRR and MOS guidance not showing much in the way of lower visibilities overnight. This may be due to an increase in low level southerly flow off the surface. Stratus development may be more likely, however, increasing cloud cover for portions of the area late. && .AVIATION...Mostly VFR. Can`t completely rule out some stratus and patchy fog development late tonight through early Friday morning, producing tempo IFR/MVFR conditions roughly between 09-13Z. However, confidence wasn`t high enough to include in the TAFs at this time. Should any fog/stratus develop, it will quickly lift and burn off after sunrise. && .MARINE...South to southeast winds around 10-15 knots will continue across the waters into tonight, with seas around 3-4 feet. && .PRELIMINARY POINT TEMPS/POPS... DAB 65 88 66 84 / 0 0 10 0 MCO 68 92 67 90 / 10 0 10 0 MLB 69 87 68 83 / 10 0 10 0 VRB 66 87 66 82 / 10 0 10 0 LEE 67 91 68 91 / 0 0 10 0 SFB 68 91 67 90 / 10 0 10 0 ORL 68 92 69 90 / 10 0 10 0 FPR 66 88 66 83 / 10 0 10 0 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Weitlich/Sedlock
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT Thu Mar 25 2021 .SHORT TERM...(This evening through Friday) Issued at 405 PM EDT THU MAR 25 2021 WV Imagery and RAP analysis indicated a broad mid/upper level trough over the west into the central CONUS and a ridge off the east coast resulting in sw flow through the Great Lakes. A vigorous shrtwv into sw Missouri was lifting to the northeast with mainly just high clouds spreading into Upper Michigan. At the surface, high pressure extended from Hudson Bay into the northern Great Lakes bringing colder air into the area on northerly winds. The shallow cold air moving in across Lake Superior also supported extensive low clouds across Upper Michigan into northern WI along with an occasional light flurry or two. Tonight, expect any pcpn from the southern stream shrtwv and sfc low to remain well to the south. However, with a slightly tighter pressure gradient and winds veering to the northeast will also strengthen. 3k ft temps around -10C will provide just enough instability for flurries or light snow showers for north central Upper Michigan, favored by upslope flow. Even though the temp profile will also be marginal for ice nuclei, expect even limited convective clouds and drier sub cloud layer will continue to favor mainly snow rather than any freezing drizzle. Friday, surface and mid level ridging building into the area with drier air and diminishing winds moving in from the west will bring an end to any light -shsn chances. Otherwise, even with some clearing in the afternoon from the west, temps will remain below average with readings in the low to mid 30s north to the low 40s south. .LONG TERM...(Friday night through Thursday) Issued at 423 PM EDT THU MAR 25 2021 A deepening surface low is expected to produce widespread light rain changing to light snow this weekend. The next feature of note is a seasonably strong cold front expected to move through late Tuesday/early Wednesday. Clouds increase early Saturday morning as a shortwave trough transports moisture into the area. A northern-stream shortwave approaches the area late on Saturday bringing a noticeably colder air mass with it. Precipitation spreads over the area from southwest to northeast during the day on Saturday associated with warm air advection forcing broad isentropic lift across the area. Differences in modeled surface low track/intensity results in uncertainty in precipitation types, but the big picture favors rain transitioning to snow as the temperature profile cools. It appears most QPF falls in the warm air advection regime of this system with only light lake enhanced precipitation within the systems decaying deformation zone. Deterministic guidance shows potential for mesoscale banding associated with substantial 850-700 mb frontogenesis. However, I feel it`s too early to get cute with placement of banding features and decided to lower storm total QPF amounts to around 1/3" across the CWA. P-type issues, relatively warm surface temperatures, and daytime precipitation onset are all working against snow accumulations with less than 2 inches expected across the CWA. Snow ends from west-to-east on Sunday as the system pulls away from our CWA resulting in a temperature roller coaster next week. Cooler temperatures and blusterly northwest winds within a broad area of cold air advection will make Sunday feel chilly. However, the cooler weather will be short-lived as a <50 knot southwesterly LLJ overspreads the area on Monday and intensifies to >55 knots Monday night. As a result, temperatures are expected to rise into the 50s on Monday and could breach 60F across the interior west on Tuesday. A cold front is expected to moves across the CWA Tuesday night bringing a much cooler air mass into the area for mid to late next week. Precipitation chances ramp up near the cold front, but amounts appear light and p-type should be predominantly rain. 12Z operational and ensemble guidance favors 850 mb temperatures falling to near or below -15C by Wednesday morning, which should be cold enough for light lake effect snow accumulations in NW wind snow belts. Once again, cooler temperatures will be short-lived as long- range CIPS analogs indicate a return to warmer and drier than normal conditions for the first week of April. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 734 PM EDT THU MAR 25 2021 N to NE flow of cold air across Lake Superior will upslope into Upper MI, supporting persistent MVFR cigs at KIWD/KCMX/KSAW for most of this fcst period. Late Fri aftn/early evening, expect these lower clouds to scatter out as drier air makes inroads with approaching high pres. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 405 PM EDT THU MAR 25 2021 Northeast winds below 20 knots will increase again to 25-30 kts across much of the lake tonight as a strong low passes by well to the south. Winds will subside below 20 kts again Friday morning. The next period of strong winds will be on Sunday over the east half when gales will be possible with a shot of cold air. Freezing spray may also develop. The active weather period will continue from Monday into Tuesday as wind gusts of 25-30 kts persist through that timeframe. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...EK AVIATION...Rolfson MARINE...JLB
Area Forecast Discussion
National Weather Service Nashville TN
833 PM CDT Thu Mar 25 2021 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Updated suite of forecast products to reflect issuance of Tornado Watch 54 through 1 AM CDT Friday. Blended latest NAMNest, CONSShort, and HRRR models per best initialization and evolution of main line of showers and thunderstorms moving across mid state region during these early to mid evening hours. Tweaked hourly temperature, dewpoint, and wind speed/direction grids. Remainder of forecast continues to be on track. && .AVIATION... 00Z TAF DISCUSSION. CKV/BNA/MQY/CSV...Several admendments probable for rounds of shwrs/tstms across mid state region thru 26/04Z. Generally VFR ceilings and vsbys expected thru 26/24Z. With continuing uncertainty of tstms moving across terminals, continue to mention vcnty tstm at terminals thru 26/04Z. With strong low level jet dynamics in place, wind shear at top of 2 Kft layer 45-55kts. During relatively same time frame, surface wind gusts to around 30kts possible. Initial sustained southerly winds 7-12kts will veer to west thru 26/24Z. Convection should end across mid state region by no later than 26/06Z. Surface pressure gradient influences should weaken by around 26/10Z. && .OHX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 1 AM CDT Friday for Bedford-Cannon- Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson- Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence- Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-Pickett- Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne-White-Williamson-Wilson. Wind Advisory until 4 AM CDT Friday for Bedford-Cannon-Cheatham- Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-Fentress-Giles- Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-Lewis-Macon- Marshall-Maury-Montgomery-Overton-Perry-Pickett-Putnam-Robertson- Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne- White-Williamson-Wilson. && $$ DISCUSSION......JB Wright AVIATION........JB Wright
Area Forecast Discussion
National Weather Service Pocatello ID
822 PM MDT Thu Mar 25 2021 .SHORT TERM...THIS AFTERNOON THROUGH SATURDAY NIGHT. A quick update this evening to decrease the chance of precipitation across the Island Park region to reduce forecast issues with Great Falls. Other than that, the upper low remains overhead and supportive of ongoing showers tonight. See the previous discussion below. Huston Widespread areas of light rain and snow continue early this afternoon across the CWA. High-res model reflectivity guidance suggests the activity will become a bit more convective/showery as the low pressure center embedded in this latest shortwave moves overhead tracking SE. We discussed whether thunder would be needed in the forecast this afternoon/eve...however, NAMNest LIs struggle to reach -1 and HREF mean MUCAPE remains below 100 J/kg with widespread cloud cover favored to continue (almost no instability), so even if we squeak out a brief heavier snowfall/rainfall rate under a core and/or a few lightning strikes, potential looks quite marginal/isolated at best and will leave thunder out. Highway grip levels are really doing well as temps have creeped up today (and snow has changed to rain as expected in the ern Magic Valley/lower Snake Plain), so plan is to let the ongoing SPS expire as scheduled at 3 PM. Some slick spots could certainly redevelop this eve as temps cool and snow showers continue, especially across mntn zones and over passes, but overall impacts shouldn`t be significant. As always, we will monitor everything closely. This evening (7 PM to 4 AM window from north to south), wind evolution across the srn central mntns into the Snake Plain does look favorable for some potential convergence-zone snowfall development, and there`s MAYBE a hint of this on the HRRR, but otherwise guidance isn`t excited about it at all. We broadbrushed some additional PoPs/light QPF into the forecast over this region to cover this just in case, with snowfall amounts generally 1/2 inch or less if development occurs, but confidence is low. We also allowed some patchy fog in the grids tonight for some valleys...the HRRR cig product/MOS guidance aren`t terribly excited about fog, but given plenty of sfc moisture and recent precip, could easily see isolated pockets. Otherwise, generally ran with NBM guidance for all parameters with few edits. A few light snow showers may linger Fri in the Bear Lake region and WY border corridor, but otherwise expect a clearing trend over the course of the day. GORGEOUS weather follows for Sat with plenty of sunshine and highs rising into the mid 40s to upper 50s (and it only gets better for Sun with highs approaching 70 for Burley and Shoshone!). - KSmith .LONG TERM...SUNDAY THROUGH NEXT THURSDAY... Gorgeous weather will be short-lived. A vigorous, fast-moving cold front is headed our way on Monday. Deterministic models remain in good agreement with the progression of the system with onset of precipitation in the 06Z- 12Z timeframe in the Central Mountains. Passing through southeast Idaho at about 35 mph, the front exits the state around 18Z Monday. Thus there should be little snow accumulation and valley rain. Best snowfall amounts are in the Central Mountains with about 3 to 6 inches accumulation on Monday. The main impact will be winds starting Sunday night. Have boosted forecast winds to a blend of MEX and the NBM 90th percentile. Winds at 700mb still in the 50 to 60 kt range ahead of the front, dropping off to 40 to 45 kts behind it. Temperatures Monday will be noticeably cooler by 15 to 20 degrees across the region thanks to the front-- also thanks to Sunday highs being well above normal! Broad ridging will build back into the region through Thursday as temps warm throughout the week. - Hinsberger && .AVIATION... Snow remains the predominant precip type at TAF issuance, but temperatures rising herald the changeover to rain or at least a mix soon. Widespread cloud cover is varying between VFR and MVFR with visibility mainly VFR, though IFR visibility is observed at KIDA at 18Z. What`s concerning is the 1/4SM visibility observed at KJER, just outside our border. Convective trends seen in the high-res models support the potential for heavier showers and possibly an isolated thunderstorm. SPC guidance extends the thunderstorm threat into the vicinity of KBYI this afternoon. Some high-res models also show the possibility of a snow band developing late afternoon/early evening between KIDA and KPIH. - Hinsberger && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$
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