625 FXUS64 KHUN 081005 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 405 AM CST Fri Jan 8 2021 .NEAR TERM...(Today) Issued at 405 AM CST Fri Jan 8 2021 Some light returns on area radars continue to gradually rotate around the upper low slowing moving into east TN. The sfc low on the other hand continues to traverse ewd across east cntrl AL into west cntrl GA. Any of this precip reaching the sfc is likely just some very light snow/wintry mix. Any lingering light precip will predom just impact portions of srn mid TN into NE AL heading into the morning hrs this Fri. With temps mainly in the lower 30s across srn mid TN into the mid 30s for north AL, any additional light snow may translate into a light dusting on grassy surfaces. This should only last for a few hrs this morning before any lingering light precip tapers off to the east with the exiting sfc/upper low. The Winter Wx Advisory in effect for srn mid TN thru 6 AM will be allowed to continue given temps across much of this area remain in the lower 30s. This will continue to result in a few slick spots on some roads and overpasses, although these conditions should improve shortly after daybreak as temps climb just above the freezing mark. Otherwise, cloudy skies look to remain in place today, with forecast time heights showing fairly sig amounts of moisture in place below H7. The upper flow pattern will begin to veer more to the NW later today, with the exiting upper low/trough axis to the east. Large area of high pressure out of the Plains states will gradually build SE in the wake of the exiting sfc low/trough. This should maintain some light CAA into the area from the NNW thru today, with afternoon highs struggling to reach the lower 40s/near 40F. .SHORT TERM...(Tonight through Sunday) Issued at 405 AM CST Fri Jan 8 2021 Little change in the overall synoptic pattern will continue into the weekend period, as the sfc high out of the Plains states gradually builds more into the Midwest/OH Valley regions. Skies look to remain mostly cloudy thru tonight/Sat, before cloud cover begins to diminish Sat night into Sun. Weak CAA will also continue over the cntrl TN Valley for much of the weekend period, as sfc flow remains out of the NNW. Lows early Sat look to fall mainly into the upper 20s, before afternoon temps later in the day struggle to climb higher than the upper 30s/near 40F. With cloud cover scattering, overnight lows into early Sun look to fall more into the mid 20s for most spots, before slightly warmer conditions develop on Sun, as highs climb into the lower/mid 40s. .LONG TERM...(Sunday night through Thursday) Issued at 405 AM CST Fri Jan 8 2021 Attention will quickly turn to a developing storm system over the Southern Plains that will shift east into the Lower Mississippi Valley and Deep South region late Sunday night into Monday. Some critical details still to resolve with this system, but the bottom line is that our area may be better positioned for at least a light winter weather event Monday morning. A couple things going our way is a favorable surface low track (western Gulf into the the Florida Panhandle) and the fact that we should have sufficiently cold air both aloft and at the surface to support some light snow. One caveat right now appears to be moisture as it may take a little while for the dry air to erode near the surface. Another caveat is where the exact placement of the deeper, colder air will be with respect to this precipitation shield Monday morning. The GFS continues to hint at this being an issue. However, it is definitely the outlier as the ECMWF, CMC, and NAM indicate a pronounced moistening of the column well into the dendritic snow growth zone by 12z or so Monday morning. Have trended the forecast a little more toward these solutions, especially with the 00z and 06z NAM now on board with an earlier onset of precipitation. Given the aforementioned factors, this precipitation would fall as light snow through most of the morning which could lead to at least some light accumulations, especially for areas west of I-65 which should have the better combination of subfreezing temperatures and stronger synoptic lift from the associated upper-low moving into the lower Mississippi Valley. If precipitation can begin eariler and occur within a favorable vertical temperature profile the better our chances for snow, mainly in the 09-15z and/or 12-18z window. ECMWF ensembles are more optimistic as one might expect with 34/50 members showing measurable snow at KMSL and 24/50 at KHSV. The GFS ensembles are a bit lower 12/30 and 9/30 respectively, with only a couple indicating any accumulations above 0.5". Models continue to struggle a bit with the temperature profile during the day on Monday as well with the NBM warming us into the mid 40s. This would subsequently change snow back over to rain much faster and minimize any possible societal impacts. However, these temperatures are likely being overdone, especially with a stout northeast surface flow progged to remain in place throughout the event. Thus, while some warming is probable during the day, think highs in the upper 30s to lower 40s might be a little more reasonable (though these values might be overdone depending on the track of the system). This is one of the most critical details we will need to figure out in the coming days, so stay tuned -- these numbers could change a little bit. There may also be a narrow window for some light wintry precipitation on the backside of this system. The main concern here would be that moisture could be more limited. This might constrain our snow chances to a brief window -- and mainly for localized areas on the Plateau of southern middle Tennessee and northeast Alabama. To summarize: feel reasonably confident in a brief window for some light accumulating snowfall on Monday given the overall pattern, but confidence is quite low for widespread accumulations above 0.5" or that we'll have any appreciable societal impacts. IF the right combination of factors come together, there is a chance we could out perform this forecast, especially in some of our western areas. However, these details are not well enough resolved at this time. Beyond the system Monday and Monday night, expect dry and benign weather as high pressure builds in from the west. We should see some air mass modification by Wednesday/Thursday as winds veer to the southwest. As a result, temperatures will warm back up into the mid to upper 50s (to go along with mostly sunny conditions). && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1055 PM CST Thu Jan 7 2021 Most of the winter weather has moved on from both terminals, but scattered light mixed precipitation will be possible overnight. Because of low confidence, this has been covered by a TEMPO with prevailing no precipitation. IFR to brief LIFR ceilings are likely to continue overnight and lift to MVFR by the afternoon with continued overcast skies. Moderate north winds may gust near 15 to 20 kts in the afternoon and become light overnight. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...Winter Weather Advisory until 6 AM CST early this morning for TNZ076-096-097. && $$ NEAR TERM...09 SHORT TERM...09 LONG TERM...AMP.24 AVIATION...30 For more information please visit our website at weather.gov/huntsville.