358 FXUS64 KHUN 050458 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1058 PM CST Tue Feb 4 2020 .UPDATE... For 06Z TAFS. && .NEAR TERM...(Tonight) Issued at 845 PM CST Tue Feb 4 2020 An amplifying upper trough now moving across the Desert SW and NW Mexico, was helping to bring unsettled weather to our region. This trough extended southward from the central High Plains to the Baja, bringing a substantial mid/high altitude moisture flow from the subtropical Pacific, rounding the southern part of the trough to across the eastern seaboard. There was somewhat of a break in the action, regarding showers impacting the Tennessee Valley. An area of heavier showers (with some thunder) was affecting areas over the LA/AR border to near Memphis. Other more widespread showers continued moving to the NE from the Mid south to the Ohio Valley. Another area of more scattered showers with a few rumbles of thunder were moving from the mouth of the Mississippi to across southern MS/AL/GA. Unseasonably mild or warm temperatures continued across the area, with 9 PM temperatures in the low/mid 60s. New 00Z model guidance was in good agreement suggesting that more showers should reform to our SW, and move across the Valley in the overnight. Did trim back on shower coverage in the early evening update, but left it alone for the midnight and beyond. The precipitation character should be mainly showers, but could have a few rumbles of thunder embedded within some of the heavier echoes. Temperatures should only cool to around 60 by daybreak Wednesday. Normal high/low temperatures this time of year are around 53/33 for reference. New guidance coming in is suggesting a potentially active day on Wed, as a developing surface low to our west brings even deeper moisture and better chances for showers and thunderstorms. .SHORT TERM...(Wednesday through Thursday) Issued at 300 PM CST Tue Feb 4 2020 There looks to be a break in activity Wednesday morning, as more mid-level dry air becomes entrained in the atmospheric column. Also, expect some stabilization from the recently departed convection moving northward into Tennessee and Kentucky. However, a more pronounced period of strong to severe thunderstorms looks to be in the cards later Wednesday afternoon into Wednesday night. This activity from along a fairly strong shortwave trough axis ahead of the main cold front over Mississippi. Given bulk shear values over 60 knots, MUCAPE between 500 and 1000 J/KG, SBCAPE values from 400 to 1000 J/KG in most guidance, and strong forcing with the shortwave and front, severe thunderstorms look possible. Given good PWATS and strong forcing, heavy rainfall between 1 and 3 inches also looks possible through Thursday morning, with locally higher amounts possible. Given ample helicity, it looks as though as modes of severe weather are possible. One or two models hint at the area possibly being cut off from better surface instability, but even if that is the case, modest elevated instability and just enough surface based instability look to be in place for a quick tornado spin up, large hail, or damaging winds. Models seem to be in better agreement that this round of severe weather will move into northwestern Alabama after 3 PM on Wednesday. This then move east across northern Alabama Wednesday night. How long this lasts into the late night hours is a bit more uncertain, but some form of a severe threat will likely preserver into northeastern Alabama given elevated instability. Models do show some post-frontal light precipitation on Thursday. The much cooler air moves into the area late Thursday afternoon into Thursday night. Keep isolated to widely scattered precipitation in the forecast overnight. This will likely change over from rain to a brief period of snow around daybreak on Friday. However, due to warm ground temperatures and the brief period of temperatures dropping to 32 degree celsius no snowfall accumulation is expected. .LONG TERM...(Thursday night through Monday) Issued at 300 PM CST Tue Feb 4 2020 The extended portion of the forecast period begins 12Z Friday with an upper low departing the area well N/E across the Ern Great Lakes, with lingering wraparound moisture still exiting the area at sunrise. Flurries are definitely possible during this timeframe with lingering moisture in place with stout CAA infiltrating the area from the NW. Thankfully, no accumulations are expected due to warm ground temps and dwindling moisture vacating the area to the E. Friday will be a cooler day, with daytime highs in the middle/upper 40s with a mix of sun and clouds. Another quick-moving disturbance will impact the area on Saturday as a piece of energy rapidly traverses the OH River Valley. This will lead to some light to moderate (at times) rainfall Saturday/Saturday evening, before a repeat of Thu/Fri occurs once again. Colder air rushing into the area in the wake of the departing shortwave will cause a quick/brief rain/snow mix Saturday night into Sunday morning. Again, no accumulations are expected due to warmer ground temps, but it should be another shot at seeing a few flakes around sunrise Sunday morning. Morning lows at this time will be in the lower 30s (but several degrees above freezing). The story for Sunday and beyond is the gradual warmup into early next week and the potential for heavy rainfall. It won't quite be like February 2019 all over again, but if the GFS verifies thru midweek next week, we'll definitely be looking at river flooding galore across the area. A stalled frontal boundary looks to set up from SW to NE across the area, sending moisture plumes a-plenty NE across the Southeastern U.S. Multiple disturbances will ride NE up this boundary, providing numerous rounds of moderate/heavy rainfall from Monday through Wednesday (at least). Some discrepancies exist between the GFS/ECMWF this far out, with the ECMWF not quite as bullish as the GFS, but still noteworthy with likely 2-4" of rainfall possible. I'm not going to entertain the amounts with the GFS just yet, but it's much worse, and this part of the forecast period will need to be adjusted in the coming days. The trend during this timeframe is for daytime highs in the lower/middle 60s and morning lows gradually warming into the lower to middle 50s (at least). Stay tuned! && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1058 PM CST Tue Feb 4 2020 There will not be ideal flying conditions tonight through tomorrow night as cigs will be low and showers and thunderstorms will be prevalent starting overnight tonight and lasting until 06Z Thursday. Expect a mix of MVFR and IFR/LIFR conditions overnight tonight as showers move into the area along a line currently to our west. Could see a few thunderstorms with this line. This line will hang over our area through the morning hours, and try to lift north midday. When it lifts north, we may see improvement to mostly MVFR cigs during this time, but this will help develop more heavier showers and thunderstorms that will move through during the afternoon and evening hours. Under heavier showers and thunderstorms, expect IFR/LIFR conditions. Could even see some severe weather, mainly between 21Z- 04Z, with the potential for strong winds, hail, and a few tornadoes. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...RSB SHORT TERM...KTW LONG TERM...CA AVIATION...McCoy For more information please visit our website at weather.gov/huntsville.