928 FXUS64 KHUN 030359 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 959 PM CST Mon Dec 2 2019 .NEAR TERM...(Rest of tonight) Issued at 959 PM CST Mon Dec 2 2019 Latest guidance continues to indicate that north-northwest flow aloft will slowly weaken and back to the west-northwest overnight, as a mid-level trough accelerates northeastward off the coast of New England. Thus, although moderately strong subsidence along the 290/300K surfaces in this regime will continue to slowly erode the stratus deck from the northwest, there is some concern that low clouds may tend to backbuild into the region after a brief period of clearing late this evening-early Tuesday morning. We have indicated this trend in the updated sky cover grids, but have also lowered the minimum temperature forecast to indicate at least a brief window for the favorable overlap of clear skies and calm winds to support radiational cooling. If stratus clouds do not backbuild into the region, temperatures in the upper 20s will be quite favorable for the development of both widespread frost and patchy freezing fog (in our larger river valleys), but there is too much uncertainty to include these elements in the forecast at this point. .SHORT TERM...(Tuesday through Wednesday) Issued at 132 PM CST Mon Dec 2 2019 A narrow mid-upper ridge will shift southeast Tuesday before another northwest flow trough axis drops southeast through the MS valley Tuesday afternoon and into the TN valley Tuesday evening. Highs will only be in the middle to upper 40s Tuesday afternoon, but an improvement over today. This next trough will produce a brief period of mid-high clouds and no precipitation. In addition, a narrow ridge of warmer air will occur along and immediately behind the trough passage, so morning lows Wednesday will remain in the lower to middle 30s. Temp advection will transition to briefly cool then back to neutral by Wednesday afternoon. High level clouds will increase rapidly Wednesday night with a fast moving impulse moving through the upper ridge position. .LONG TERM...(Wednesday night through Sunday) Issued at 132 PM CST Mon Dec 2 2019 Northwest flow will persist through the day on Thursday as a weak upper disturbance/shortwave tracks east over the Southern Plains. An increase in moisture aloft will lead to an increase in mid to high level clouds late Thursday afternoon into the overnight hours. High temperatures will approach 60 degrees across much of the area Thursday, and overnight lows will drop into the upper 30s/low 40s. Clouds will help keep high temps a few degrees cooler on Friday, and the aforementioned disturbance will bring chances for showers on Friday. Have maintained likely PoPs in NW AL and counties south of the TN River for now, but these may need to be tweaked down some if guidance continues to trend drier and farther south. Thermodynamic profiles do not support thunder at this time, and PW values < 1" indicate this will not be an efficient rain producer. Rain will come to an end by Friday evening, and clouds will begin thinning overnight. Not much change in the way of temperatures over the weekend, as we look to remain a degree or two above seasonal norms. A stronger system looks to be in store toward the end of the weekend and beginning of the work week, resulting in a return of cloud cover and rain chances. With that said, inconsistencies within long term guidance prohibit anything higher than likely PoPs at this point. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 623 PM CST Mon Dec 2 2019 Recent trends in satellite imagery suggest that an overcast stratus deck will remain intact across the region overnight, and perhaps for much of the morning on Tuesday due to lack of appreciable boundary layer mixing beneath an inversion. Using a blend of data from forecast soundings, we have indicated rapid clearing of the stratus deck to occur in the 03/16-18Z timeframe, but this may need to be adjusted by an hour or so in either direction. Although cigs will predominately be in the low-VFR range (3000-3500 ft AGL), they will periodically descend to MVFR levels beginning late this evening. An overcast cirrostratus layer will be in place as the stratus deck begins to clear, with VFR cigs at FL200 expected for the remainder of the TAF period. NNW sfc flow arnd 10 knots will become lgt/vrbl overnight, before assuming a WSW component tomorrow in advance of an approaching cold front. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...70/DD SHORT TERM...17 LONG TERM...25 AVIATION...70/DD For more information please visit our website at weather.gov/huntsville.