504 FXUS64 KHUN 091133 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 633 AM CDT Mon Mar 9 2020 .UPDATE... For 12Z TAFS. && .NEAR TERM...(Now through Today) Issued at 250 AM CDT Mon Mar 9 2020 Currently, quiet and benign conditions are in place as the surface ridge axis extends through Central AL. Weak SE flow and mild temps will persist through sunrise. Further west, a developing shortwave over the western Plains is gradually taking shape. As this wave propagates eastward, deep southwesterly flow through the midlevels will persist over the TN Valley, helping to usher in some excess moisture from the Gulf and steadily increase cloud cover throughout the day. With the storm system approaching the Mid MS River Valley by this evening, lift/upglide will favor increasing rain changes, mainly focused on NW AL through tonight. .SHORT TERM...(Tonight through Tuesday Night) Issued at 250 AM CDT Mon Mar 9 2020 The aforementioned storm system continues to track towards the Great Lakes region and drag an attendant cold front through Mid MS Valley and NW portions of the TN Valley through Tuesday. Ahead of this front, better instability will be realized and can tap into the warm airmass over the region to support the potential for some afternoon and evening thunderstorms. Decent lapse rates, surface CAPE ~750 J/kg, but weak shear will at least give the risk of gusty winds and potentially small hail with the strongest of storms. The thunderstorm trend will lessen after sunset on Tuesday as instability parameters weaken. However, lingering moisture will keep at least a slight chance of rain in the forecast for Tuesday night/Wed. morning. Temps will trend a few degrees above early March values in both afternoon highs and nightly lows. .LONG TERM...(Wednesday night through Sunday) Issued at 250 AM CDT Mon Mar 9 2020 West-northwest flow aloft will continue on Wednesday into Thursday. This will bring a series weak shortwaves from the central Plains through the TN valley. One wave arrives during the afternoon hours which may help trigger a few strong thunderstorms as the warm sector destabilizes and afternoon temps rise into the lower 70s. Steepening low level lapse rates and SBCAPEs of 1000-1500 j/kg are possible with deep layer bulk shear values of 40-50kt. This could yield hail in a few of these storms into the early evening hours. Fortunately, low level wind/shear fields are rather weak. The NAM indicates an MCS that develops earlier in the day over the Ozarks which may attempt to travel east-southeast into the area Wednesday evening. However, this evolution remains a bit murky as the upper shortwave support will be lacking by that time. The medium range models continue to diverge on handling of the synoptic pattern Thursday into Friday. The GFS is still showing a more dominant trough sweeping through the Great Lakes and stronger cold front/ridge building into the TN valley and Southeast. This suppresses showers and thunderstorms to our south temporarily late Thursday into Friday. Meanwhile, the ECWMF sinks the front slower into the region on Friday with a continued threat of showers and thunderstorms. Then, the front lifts north in advance of the ejecting Southwest U.S. shortwave Saturday before a cold front attempts to push through Sunday. So, in a nutshell, still plenty of uncertainty on all of this and how/when it occurs. Thus, suggested blends will keep daily PoPs through the period with rather mild temperatures. And, it appears that a strong upper high over the western Caribbean will maintain an active west-southwest flow aloft across the South and Southeast early next week as well. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 628 AM CDT Mon Mar 9 2020 VFR conditions currently prevail and will persist through the morning and early afternoon. Surface winds will gradually veer and become more southerly, and gusty this afternoon, as surface ridging is forced east ahead of an approaching storm system. Given the increase in Gulf moisture, clouds will steadily increase throughout the day, becoming BKN in the mid and upper levels. Expected -SHRA to be introduced around 00z, mainly focused in NW AL, and persisting through the TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...Barron SHORT TERM...Barron LONG TERM...17 AVIATION...Barron For more information please visit our website at weather.gov/huntsville.