Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
432 FXUS64 KHUN 201729 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1129 AM CST Mon Nov 20 2017 .UPDATE... For 18Z TAFS. && .NEAR TERM...(Rest of Today) Issued at 847 AM CST Mon Nov 20 2017 With an exception of locations just downwind of large bodies of water, a growing season hard freeze affected nearly all of the Tennessee Valley last night. The lowest temperature noted thus far was 19 in Winchester, with just about all other locations having lows of at least 28 degrees. As of the present, temperatures across the forecast area have risen above 32 degrees. As such, a Non- Precipitation Warning for Freezing temperatures was allowed to expire at 8 AM. The forecast otherwise for the rest of the day should feature slightly warmer temperatures, as generally sunny skies prevail across the the southeast CONUS. A shield of high clouds associated with a slight dip in the upper jet should persist through the day. High temperatures later this afternoon should rise into the low/mid 50s, a category or two warmer than yesterday. Lighter winds from the southeast and south will make for more comfortable conditions for those working outdoors today. The removal of the Freeze Warning and minor forecast updates for today were recently sent. .SHORT TERM...(Tuesday through Wednesday night) Issued at 233 AM CST Mon Nov 20 2017 By this point in the forecast (Tuesday), a sheared mid-level shortwave moving within the northwesterly flow over the northern Plains will rapidly move underneath a deepening shortwave trough over the Great Lakes. Meanwhile, low-level clouds are expected to develop just off the coast of GA and move northwest towards eastern Alabama. Antecedent southeasterly flow will advect modified air towards the TN Valley on Tuesday which combined with the daytime heating will mean daytime highs should reach into the low 60s. It is possible that some very light precipitation could reach the ground over northeast Alabama on Tuesday afternoon within the 'warm air' advection zone, but due to the very dry airmass in place, not confident enough to include in the forecast. A reinforcing cold front moving ahead of the shortwave trough moving over the Midwest on Tuesday is expected to arrive over the TN Valley on Tuesday night into Wednesday morning. Forecast soundings and moisture transport products do show the potential for cloud cover both at the low-levels (above 850 mb) and mid-levels pre- and post- frontal. Nevertheless, these same profiles also show very dry surface layers. So, will keep the dry forecast. The primary change will be to the temperatures on Wednesday. Current guidance is cooler with the daytime highs post-frontal passage on Wednesday morning. Given the source region and speed of this front, incorporating highs in the mid to upper 40s (NW) and low 50s (SE). In addition, northerly winds of 10-15 MPH will make it feel cold on Wednesday. After sunset, temperatures should drop quickly below freezing again which will given a cold start to Thanksgiving Day. .LONG TERM...(Thursday through Sunday) Issued at 233 AM CST Mon Nov 20 2017 A dry and seasonably cool weather pattern will remain over the region from days 4-7. The trough in the eastern Gulf of Mexico will be enhanced by another shortwave dropping south on Thu-Fri with a Gulf surface low becoming more defined and lifting northeast across the FL peninsula on Friday into Saturday. The surface ridge planted across the southern into the east central CONUS will narrow and weaken during this time as another cold front drops southeast through the OH into the TN valley. This as amplification of the upper trough over the eastern CONUS occurs. Timing of this frontal passage looks to be on Saturday afternoon and will likely be precip- free. After highs in the 50s Thursday and Friday, we may reach the lower 60s just before this front passes, then decline again into the upper 40s to lower 50s for highs on Sunday, followed by another freeze Sunday night into Monday morning. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1129 AM CST Mon Nov 20 2017 Surface high pressure moving eastward across the region will continue to produce VFR weather for the TAF period. Scattered to occasionally broken high altitude clouds will affect the region into Tuesday morning, as a weak upper system moves across the SE States. Light SE winds today will become light/variable tonight, then light from the south a few hours after daybreak on Tuesday. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...RSB SHORT TERM...SL.77 LONG TERM...17 AVIATION...RSB For more information please visit our website at weather.gov/huntsville.