Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/25/20

Area Forecast Discussion
National Weather Service Birmingham AL
722 PM CDT Tue Mar 24 2020 .UPDATE... For 00Z Aviation. && .SHORT TERM... /Updated at 0237 PM CDT Tue Mar 24 2020/ This afternoon through Wednesday. Ingredients are coming together for a very active period of severe weather this evening for areas along and north of I-20. The airmass across central Alabama has been baking under a warm low level southwest flow all day with temperatures reaching the upper 70s to lower 80s. Despite heating, surface dewpoints been steady in the lower to middle 60s throughout the day, indicating a fairly deep moist layer near the surface. 12Z JAN/BMX soundings show capping inversion just below 700mb, which has kept a lid on convection through the early afternoon. Latest radar scans show convection breaking out over northern MS where surface based CAPE was near 1500 J/kg. Becoming increasingly concerned about tornado potential over northwest counties of central Alabama. Hi-res models are showing more discrete supercell development over northeast MS later this afternoon. Forecast 0-3km EHI values across the northwest counties are also increasing with current runs of the HRRR model. The discrete cells should organize into a broken line of storms by 9 or 10 pm with a lower threat of tornadoes, but still showing rotating cells within the line. Extended severe threat until midnight due to the threat of ongoing severe storms across east Alabama. Everything should be winding down quickly by midnight as low level flow weakens veers and weakens. The remaining showers and thunderstorms should exit east Alabama by sunrise Wednesday. Decreasing clouds and slightly cooler temperatures on Wednesday with highs ranging from the lower 70s north to lower 80s south. 58/rose .LONG TERM... /Updated at 0350 AM CDT Tue Mar 24 2020/ Wednesday night through Monday. Post-frontal, dry conditions will be in place across the Southeast Wednesday night as the surface low moves eastward into the Atlantic while the east to west oriented cold front continues southward through the Florida Peninsula. Weak, cool air advection and northwesterly flow will allow temperatures to decrease into the upper 40s northeast and 50s elsewhere on Thursday morning before rising sharply after sunrise as a 593dam ridge builds over the Gulf of Mexico. A surface high will develop over the Mid-Atlantic and may produce weak cool air damming over northern parts of Georgia which would keep temps a few degrees cooler across our northeast. Nonetheless, height rises, warm southwesterly low-level flow, and dry, subsident air will accompany this setup, allowing for afternoon highs around 15 degrees above average for this time of the year with temps topping out in the 80s area-wide on Thursday and Friday. This occurrence would challenge a few of our daily high records for both days. Meanwhile, an upper low over the Central US will track towards the Great Lakes Region on Saturday with a surface front reaching the Lower Mississippi Valley early Saturday afternoon. Guidance has trended towards better agreement in a late Saturday frontal passage across the forecast area, so PoPs were raised during this time frame with early evening thunderstorms possible before instability wanes after dark. There are still some uncertainties with this system, but severe weather is not expected at this time. Cooler temperatures and a short break in the rain are expected behind the front for the start of next week, but guidance indicates another system will approach the area beyond this period. 86 && .AVIATION... 00Z TAF Discussion. Added an AMD NOT SKED to all terminals this package. This was due to a technical issues with data. Most likely will eventually add some amendments in the next 2 hours. Convection ahead of a cold front will slowly move into Central Alabama through 06z. The storms will affect all the northern terminals in this period. Some of the storms may be severe with gusty winds, hail and tornadoes. At this time, the terminals have a tempo for 1sm ts. The storms will move southeastward through the evening and start to dissipate and pull eastward before impacting TOI. Ceilings will drop to MVFR as the storms arrive. After the front, ceilings drop again to IFR and hold there north through 15-18z. Winds will be southwest around 10 kts and gusty then shift to the northwest at 5-10kts. Some VFR looks likely by afternoon. Southern sites will have a lesser chance of rain or storms and then drop to MVFR ceilings. 75 && .FIRE WEATHER... Scattered to numerous showers and thunderstorms will spread across north Alabama tonight. Some of the storms could be severe, mainly along and north of I-20. A weakening band of showers and storms will push into the southern counties after midnight. A weak cool front will bring drier and slightly cooler air into central Alabama on Wednesday. Warmer conditions on Thursday and Friday with no rain expected. Despite highs in the 80s Thursday and Friday, afternoon humidity levels will only fall into the 40-50 percent range. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 57 73 48 79 59 / 90 10 0 0 0 Anniston 60 74 50 80 60 / 90 10 0 0 0 Birmingham 59 74 52 82 63 / 90 10 0 0 0 Tuscaloosa 60 76 53 84 62 / 90 0 0 0 0 Calera 60 75 52 82 62 / 90 10 0 0 0 Auburn 63 76 54 80 60 / 60 10 0 0 0 Montgomery 65 80 55 86 62 / 50 10 0 0 0 Troy 65 81 56 85 62 / 20 10 0 0 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Tue Mar 24 2020 .AVIATION... An area of low level moisture will accompany a frontal boundary across the southeast Michigan overnight. The resulting coverage of low stratus may prove chaotic at times given recent trends, but continue to support a generally broken condition during the early- mid morning hours. Restrictions held in MVFR with some lowering below 2000 ft possible near daybreak. Warmer air lifting into the region as flow veers to south/southwest will eventually support a general clearing trend late morning/early afternoon Wednesday. For DTW...Lower stratus will exist through the early-mid morning hours, then increasing likelihood for clearing after 14z-15z. .DTW THRESHOLD PROBABILITIES... * High for ceilings at or below 5000 ft tonight. Low Wednesday morning. && .PREV DISCUSSION... Issued at 341 PM EDT Tue Mar 24 2020 DISCUSSION... Surface high pressure is currently centered over the stable lake aggregate from the Lake Huron basin southward through central Lake Erie. No tangible weather to speak of other than varying coverage of opaque stratus. Model soundings and plan view persecptive show unidirectional easterly flow in the lowest 5000 ft of the column. The lack of anticyclonic flow trajectories has really limited any active lower column subsidence from penetrating downward into the sub inversion layer and any shot at widespread saturation/cloud dissipation. Instead the area remains under the effect of residual cool drainage flow off of the anticyclone to the east. Will continue to favor a higher sky fraction forecast for the remainder of today. Uncertainty exists for tonight with regard to cloud forecast. Rap soundings show fairly convincing signal for loss of saturation with nightfall. Difficult to outright discount this idea as much of the cloud north of Metro Detroit is appearing convective from diabatic heating. South of M 59 cloud is much more laminar and there is a 850- 775mb thermal discontinuity to the south. Models show veering of the wind directions to more southerly tonight which will allow the weak frontal feature to push directly into the area. Latest fleeting thought is that clouds will dissipate somewhat quickly this evening north of M59, clouds will hold south this evening before lifting northward overnight. Residual surface high pressure enhanced early by ridging dipole off Ohio River low pressure will persist over Southeast Michigan for a good portion of Wednesday. Differential height rises will balloon into Lower Michigan during the latter half of the day which will force low level warm advection directly into the area on increased southwest gradient flow. The warm advection will erode out lingering sub-inversion saturation and cloud. Expecting rapid loss to any remaining cloud late Wednesday afternoon and evening. Strong warm advection collocated with amplifying shortwave will bring a period of ascent and precipitation to the northern Great Lakes. The question remains how far south precipitation will fall as consensus of solutions has been relatively dry for the cwa. The period of concern for the northern wave precipitation chances is centered around 12Z Thursday morning. Blended guidance and model QPF output are a mess. Forecast soundings show a very narrow saturated layer on elevated front, with pleny of dry air concerns at the surface. Forecast soundings also show very active midlevel subsidence indicative of a very strong background for frontolysis based on rapid evolution of unfavorable jet forcing aloft. Main narrative is one of a low chance PoP, tied to some potential for sprinkles. Low confidence portion of the forecast is where exactly precipitation will be supported along a baroclinic zone that becomes increasingly organized south of the Michigan border late Thursday through early Saturday. Pattern recognition and some model data supports strong subsidence holding locally with frontal zone being suppressed to the south. Initial jetlet on amplified ridge is expected to bring an ageostrophic response and wave of low pressure along the front late Thursday. Blended guidance is again difficult to work with and too broadbrushed, but consensus calls for main window for precipitation for some late Thursday night, then waiting until Saturday night and Sunday. Plenty of time exists to work out details on storm system amplitude for the weekend. MARINE... High pressure remains in control across the Great Lakes as it drifts east into New England, resulting in calm to light winds. A series of low pressure system will then travel close or over the Great Lakes region Wednesday through the end week period. Passage of these lows will result in a slight uptick in wind speeds and wave heights but look to hold well below threshold values. Otherwise, return flow from the departing high will lock easterly flow in place today before turning more southwest to south late Wednesday into Thursday following the passage of a warm front. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....MR DISCUSSION...CB MARINE.......AM You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Peachtree City GA
938 PM EDT Tue Mar 24 2020 .UPDATE... Second round of convection pushing into north Georgia with scattered showers and isolated thunderstorms expected to push to the south and east across the area through early morning hours. A Tornado watch remains in affect for portions of northwest Georgia through 1 am. Only minor tweaks made to hourly temperatures and winds this evening. Updated forecast products issued shortly. && .PREV DISCUSSION... /Issued 343 PM EDT Tue Mar 24 2020/ SHORT TERM /Rest of today through Wednesday Night/... Main focus of fcst will largely be the strong to severe storm threat in the near term and tonight period. An upper shortwave looks to amplify some across the area late this afternoon into overnight. While a lingering wedge has persisted in the northeast, mainly from northern half of the Atlanta Metro over to Athens and northward, the other portion of the CWA has had more destabilization with some scattering of stratocu and increased daytime heating. The RAP even has an axis of progged SBCAPE getting up to near 1500 J/kg going into this evening ahead of the trough. With ample low and deep layer shear expected, the Slight to Marginal severe outlook looks well justified for damaging winds with any bowing segments, along with hail and isolated tornado threats. The HREF probs for STP greater than 1 do get above 90 percent for late afternoon into evening across mainly western portions of the CWA, though any localized interaction with the aforementioned wedge front could focus an increased risk for stronger rotating convection and will need to be monitored. Otherwise expecting a drying postfrontal regime for Wednesday and a switch to NW flow aloft. Should still be pleasant above normal temps getting into the 70s for most areas then lows in the upper 40s to 50s Wednesday night. Baker LONG TERM /Thursday through Tuesday/... The highlights of the extended forecast are above average temperatures with a couple dry days followed by a late weekend frontal passage. The forecast picks up on Thursday morning with northwesterly mid- /upper-level flow and a surface high sinking providing dry conditions through Friday. South to southwesterly lower and upper level flow returns on Saturday ahead of developing surface low over the Midwest region. PoPs increase through the day Saturday into Sunday as the associated cold front approaches and sweeps through the CWA. Models have come into better alignment with the timing of this system with some minor discrepancies in precipitation amounts, ranging between .01 and .25 inches. Medium range models bring in quasi-zonal flow with a weak surface high over the Ohio River Valley on Monday then begin major to have major disagreement through the rest of the extended forecast. Currently, the GFS has the development of a faster and more progressive mid-level over the Appalachians on Tuesday while the ECMWF has a more amplified mid-level trough with a surface low developing over the SE. Regardless, rain chances look to continue into early next week even though confidence remains low on potential system impacts. High temperatures should remain above average through the period, except on Sunday and Monday, thanks to the aforementioned cold front. Lows should remain above average through the rest of the extended. Morgan AVIATION.../Issued 754 PM EDT Tue Mar 24 2020/ 00Z Update... Mostly VFR across the TAF sites, with LIFR over areas east of ATL including AHN. Expect a brief improvement over the LIFR area ahead of the area of showers/isolated thunderstorms which should move across the TAF sites 05-11Z. Northern sites (ATL/RYY/PDK/FTY/AHN will drop to IFR after the storms move through with improvement to MVFR/VFR between 12-15Z. CSG/MCN will see MVFR with improvements after 14Z. Winds will shift from the SW at 10kts with some gusts to NW at 5-10kts after 12Z. //ATL Confidence...00Z Update... Medium confidence all elements. Atwell && .PRELIMINARY POINT TEMPS/POPS... Athens 60 58 74 51 / 50 80 20 5 Atlanta 78 60 72 52 / 100 80 20 5 Blairsville 60 52 65 46 / 90 90 30 5 Cartersville 68 58 71 49 / 30 90 20 5 Columbus 83 65 79 56 / 0 50 20 0 Gainesville 56 55 71 50 / 80 90 20 10 Macon 82 64 79 54 / 5 50 20 5 Rome 72 57 71 49 / 60 90 10 5 Peachtree City 82 60 74 51 / 30 80 20 0 Vidalia 83 68 82 57 / 0 30 30 5 && .FFC WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 6 AM EDT Wednesday for the following zones: Catoosa...Chattooga...Dade...Dawson...Fannin...Gilmer... Gordon...Lumpkin...Murray...Pickens...Towns...Union...Walker... White...Whitfield. Tornado Watch until 1 AM EDT Wednesday for the following zones: Bartow...Catoosa...Chattooga...Dade...Floyd...Gordon...Murray... Polk...Walker...Whitfield. && $$ SHORT TERM...Atwell LONG TERM....Morgan AVIATION...Atwell
National Weather Service Hastings NE
627 PM CDT Tue Mar 24 2020 .SHORT TERM...(This evening through Wednesday) Issued at 307 PM CDT Tue Mar 24 2020 Aloft: Animation of WV imagery and RAP tropopause analyses showed zonal flow over the CONUS. A fairly deep shrtwv trof was aprchg the Pac NW coast. This trof will slowly migrate into the Wrn USA thru tomorrow...but the flow downstream over NEB/KS will remain zonal with just a touch of anticyclonic character. Surface: 1000 mb low pres was near Lk Winnipeg with a sfc trof extending S into Wrn NEB/KS. Its cool front extended back into MT. The low will head NE to Hudson Bay thru tomorrow. Meanwhile...the sfc trof will move into the CWA and weaken while the cool front sinks thru the Nrn Plns tonight. By 00Z/Thu...the front will stretch roughly W-E acrs Nrn NEB. A new lee low is also fcst to form over Ern CO. Tonight: Mostly clear. There could be some mid-lvl alctocu floating thru after midnight. Temps will be mild...about 10F above normal. Low stratus remains over the E 1/4 of the CWA...where dwpts will not mix out this afternoon like further W. This means some fog will be psbl again late...but it won`t be as widespread as the last 2 mornings. Wed: Probably some fog to start E 1/4 of the CWA. Otherwise... sunny and very warm. Widespread 60s/70s. .LONG TERM...(Wednesday night through Tuesday) Issued at 307 PM CDT Tue Mar 24 2020 Aloft: The GFS and EC ensemble means are indicating the the Wrn USA trof will slowly advance thru the Wrn USA thru Fri...and then cross NEB/KS Sat. There are some indications a closed mid-lvl low could form as this trof passes by. Therefore...the flow aloft will progressively become more SW. As has been the case for the last 4 months...the longwave trof will remain over the Wrn USA...with the ridge over the E. Heights will recover some Sun as a shrtwv ridge moves thru ahead of the next trof that is fcst to be moving into the Desert SW. That trof will probably arrive here Mon. Model assessment: The last 3 runs of the GFS-FV3/EC/CMC/UKMET are tightly-clustered with minimal spread thru least over the CONUS. There are huge diffs upstream over the N Pac by that time though...even with the last 2 EC runs! By Sun appreciable diffs appear on the handling of the trof fcst to come out of the Desert SW. The last 2 EC runs are deeper and slower with a closed low forming...while the 06Z/12Z GFS-FV3 are open and faster. That uncertainty will need to get ironed out before we can say much about the sensible wx here next Mon. Fcst confidence is extremely low beginning next Mon. Surface: The cool front over Nrn NEB at 00Z/Thu will drop S thru the CWA Wed eve and then stall acrs Srn KS thru Fri. Canadian high pres will be to the N while svrl wk lows form and move E along the front. The final and deepest low will eject SW-NE acrs KS Fri night and into IA Sat. The 12Z EC/GFS-FV3 are very similar on the track and intensity around 990 mb 12Z/Sat-00Z/Sun. If this is correct...we may have a heavy/wet snow and wind problem on our hands. With all the uncertainty referenced above...don`t want to speculate much on next Sun-Tue. Temps: The official fcst is near normal thru Sat...then above normal Sun-Tue. However...both MOS and mdl 2m temps suggest slightly cooler than normal Thu-Sat due to extensive cloud cover. And if it snows Fri night into Sat...all bets are off for high temps Sat. It could be 10-15 colder than what we`re currently fcstg. Precip: Nothing of significance expected before Fri. NBM (which populates most of our POPs) looks way too high on precip chances Thu night into Fri morning. Any precip in that time frame will probably be drzl...if anything occurs at all. The way things are looking now...steady rain will overspread the CWA Fri night and change to snow before ending Sat. Typically...once snow starts falling with systems of this doesn`t change back to rain as the mdls are currently suggesting Sat afternoon. Suggest everyone keep a close eye on the fcst Fri night into Sat as things are currently looking threatening for accumulating/plastering wet heavy snow and windy conds. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday) Issued at 622 PM CDT Tue Mar 24 2020 Main concern through the TAF period will be some low level wind shear late tonight into Wednesday morning. Winds will increase in the morning and turn toward the west or northwest as a front moves through the terminals. && .FIRE WEATHER... Issued at 307 PM CDT Tue Mar 24 2020 Confidence is high that near critical fire wx conds will occur over the SW fringe of the CWA Wed afternoon. Confidence is medium that critical conds could occur. Opted to post a Fire Wx Watch. The main factor will be mixing heights. Deeper mixing could result in lower RH and higher winds than are currently in the fcst. If that occurs...a RFW will be needed. && .GID WATCHES/WARNINGS/ADVISORIES... NE...Fire Weather Watch Wednesday afternoon for NEZ082-083. KS...Fire Weather Watch Wednesday afternoon for KSZ005-017. && $$ SHORT TERM...Kelley LONG TERM...Kelley AVIATION...JCB FIRE WEATHER...Kelley
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
706 PM CDT Tue Mar 24 2020 .SHORT TERM...(This evening through Wednesday night) Issued at 300 PM CDT Tue Mar 24 2020 Main concern in the short term remains rain to snow potential Wednesday into Wednesday night. Radar showing last vestiges of showers exiting the northeast CWA this afternoon. Trend in the HIRES models and less so the HRRR had some redevelopment over eastern South Dakota this evening, moving into west central MN. Some MUCAPE to 400 J/kg forecast to move into that region well and an isolated thundershower possible into the early evening far west central MN. Clouds will likely linger over the area as well, with some fog possible later tonight. Surface cold front progged to drop into central MN Wednesday afternoon. Model trends continue to show fairly rapid rain/snow changeover across central MN, most likely by Noon. Strong FGEN develops along the boundary and we could see snowfall rates around 1 inch an hour if the column cools quick enough to generate wet snow. Currently have 1-2 inches from southwest into central MN with the higher totals where the transition occurs first over the southwest. Will need to monitor tonights model run to see if the cooling trend continues. The snow exits to the east Wednesday evening, with perhaps some wet snow accumulation on grassy areas around the metro. .LONG TERM...(Thursday through Tuesday) Issued at 300 PM CDT Tue Mar 24 2020 Following the Wednesday system, we work some weak high pressure over the region for Thursday. Later Friday, we the next storm system develop to the southwest and lift into the Central Plains by Saturday morning. This should spread another precipitation shield over the area Later Friday and lingering into Saturday. At the moment, deterministic models have been trending wetter rather than white. The 12z ECMWF was a bit slower and cooler eventually, which should portend to the possibly of wet snow accumulation. Still early to follow and model solution, especially on the warmer Spring system. Will need to monitor trends the next few days. Still looks like the overall temperature trend remains warmer than normal through the period. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 706 PM CDT Tue Mar 24 2020 Complex period ahead with a front moving through tonight that stalls out near the IA border Wednesday, when a surface low will work across it, spreading a large shield of precip across the area. For tonight, we will likely see scattered showers, and possibly even a thunderstorm, work through with the front, though confidence is low in coverage of showers along the front. Several hi-res models show some clearing behind the front, with the potential for dense fog forming, though this is a pretty low confidence scenario. For Wednesday, rain arrives in the morning. Trend from the HRRR, along with the RAP and 18z GFS/NAM is for a warmer, more rain scenario tomorrow, along with precip likely remaining southeast of AXN. In addition, we are seeing a slowing trend with the timing. KMSP...One trend we are seeing with the rain Wednesday is that it is forecast to reach MSP a bit later, possibly not until the afternoon. Low confidence with cig trends Wed morning as we could see a period of VFR conditions behind the fropa before the main precip shield arrives in the afternoon. /OUTLOOK FOR KMSP/ Thu...MVFR cigs in mrng, bcmg VFR in aftn. Wind E 5 kts. Fri...Chc MVFR cigs. Wind SW 5 kts. Sat...MVFR/IFR with RA. Wind NE 15G25 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...DWE LONG TERM... AVIATION...MPG