706 FXUS64 KHUN 232015 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 215 PM CST Mon Dec 23 2019 .NEAR TERM...(Tonight) Issued at 214 PM CST Mon Dec 23 2019 The broad low pressure system moving along the Gulf Coast will continue moving off to the east, gradually clearing skies west to east across Northern Alabama and southern Middle Tennessee. High pressure starts to build in, weakening northerly winds. This will allow for temperatures to drop down into the low-to-mid 40s by Tuesday morning. .SHORT TERM...(Tuesday through Wednesday) Issued at 214 PM CST Mon Dec 23 2019 High pressure building over the southeastern U.S. will mean sunny skies and warming temperatures starting on Tuesday. The ridge positions itself well centered over Alabama on Tuesday, with increasing geopotential heights leading to warming temperatures across the region. Highs starting on Tuesday will be well above normal for this time of year, with high temperatures forecast to be in the mid-to-upper 60s. The ridge starts to break down on Wednesday, and moisture starts to stream up from the southwest. This will bring in some high clouds, but with the warmer air mass still in place, and no cold air advection, expect warmer than normal temperatures to continue through Wednesday. .LONG TERM...(Wednesday night through Sunday) Issued at 214 PM CST Mon Dec 23 2019 The long-term portion of the forecast period begins Christmas night, with temperatures a degree or two milder than Wednesday morning, with temperatures only falling into the middle to upper 40s. This is thanks to the upper ridge pushing across the area, with clouds beginning to overspread the area through the day ahead of the next approaching storm system over the Desert SW. S/SW winds aloft will pump in a warmer and more moist airmass as well, making for a cloudy (but warm) Thursday across the TN Valley as clouds increase in earnest. Dry weather will continue during this time frame, with temperatures soaring about 15-20 degrees above normal for this time of year (typically in the low 50s for mid/late Dec.). It's at this point that models diverge with their solution for the weekend rainfall associated with the Desert SW system. Yesterday, we had two completely different solutions, with the GFS (Sat/Sun) being about 24-36 hours ahead of the ECMWF (Sun/Mon). Today, those solutions have come together a little better, with the ECMWF speeding up just a tad (tracking further S) and the GFS slowing down a little (tracking further N), making for better consistency in the evolution/timing of the approaching system. Though I truly believe that the GFS evolution will mostly win out given the strength of the upper level ridging strengthening over the W Coast and pushing the system through the CONUS/to the Great Lakes faster, some compromise was made to blend in with surrounding offices to blend the GFS/ECMWF for the weekend timeframe. While a dry forecast is expected Friday, WAA will increase across the area as the low deepens to the NW, and a few showers are possible Friday night into Saturday (though the brunt of the precip will hold off until after sunset Saturday). The heaviest rainfall will occur Saturday night into Sunday, further aggravating any lingering tributary/river flooding ongoing from earlier in the week. Soils will be nearly saturated, so a flooding threat will need to be monitored this weekend. The cold front will have pushed E of the area by Sunday night into Monday, with the upper trof swinging thru the region by Tuesday morning. Morning lows will fall to within 5-7 degrees of normal by this time in the wake of the front, falling into the middle to upper 30s (with normal values hovering the lower 30s). More adjustments will be warranted for this timeframe this week as model guidance comes into better agreement, so stay tuned for future forecast updates! && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1225 PM CST Mon Dec 23 2019 Predominantly VFR conditions to continue. Occasional sprinkles still could possibly bring cigs down to MVFR at HSV, but probably won't. Therefore, have left this out of the TAF. With gradually clearing skies this afternoon, VFR conditions will continue. Clear skies and calming winds could mean some fog develops overnight and lasts into Tuesday morning, especially in river valleys. Fog could possibly impact MSL, but confidence is not high enough to include in the TAF at this time. We will continue to investigate and may include in later TAF package. Any fog should lift and clear out by around 15-16Z. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...12/McCoy SHORT TERM...12 LONG TERM...12 AVIATION...McCoy For more information please visit our website at weather.gov/huntsville.