268 FXUS64 KBMX 142348 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 548 PM CST Wed Nov 14 2018 .UPDATE... For 00Z Aviation. && .SHORT TERM... Through Tonight. Inverted surface troughing across east Central Alabama is beginning to close off as a surface low over north Alabama, in response to a deepening upper level low crossing Arkansas. Deep southerly to southwesterly flow continues to bring moisture northward, over top a cold surface layer, as evident by the inversion seen below 900mb on this morning's sounding from KBMX. As this system lifts northeastward tonight toward the Ohio River Valley, rainfall will slowly end from west to east. Made some adjustments to temperatures trends tonight, and now expect temperatures near or below freezing across the northwest as early as 9PM. Also added St.Clair county to the Freeze Warning. It could take a while for locations across the north to warm above freezing Thursday, and have extended the Freeze Warning til Noon. While temperatures will be cold, wind chill values in the morning (around sunrise) will be in the 20s for most of the area, and in the low 20s for locations west of I-65. What about the potential for frozen precipitation tonight? Temperatures across the northwest have hovered in the mid 30s this afternoon, and at times, observation sites there and in northeast Mississippi have reported unknown precip. The inversion just above the surface dips as low as -4 degrees C through the afternoon, and a few sleet pellets are possible. That cold layer will deepen this evening as a mid and upper level dry slot pushes eastward, eroding deeper layer moisture. As temperatures above the surface become more favorable for a wintry precipitation mix, moisture will be quickly pulling away from the area. Did add a mention of sleet (now carrying a low chance of a rain shower/sleet mix) for portions of the far north as the rainfall ends. Expect the rain/moisture to exit in the east before the cooler air has a chance to advect that far into the area. Do not expect accumulation of frozen precipitation, as ground conditions remain relatively warm. 14 .LONG TERM... Thursday through Tuesday. Models have trended a little colder on Thursday with strong cold advection ushering in 925mb temperatures as low as -8C. Steep surface to 925mb lapse rates will help maintain a deck of stratus through the morning hours. Some clearing is expected during the afternoon across the western and southern counties as the core of the strongest cold advection shifts eastward. This should allow temperatures to rise into the 40s in those areas, but clouds are likely to linger in our northern and eastern counties, where afternoon highs have been lowered into the upper 30s. Wind chills in the 20 to 28 degree range are expected for the vast majority of the forecast area through noon Thursday. If the temperature at Birmingham fails to reach 40F, this will tie a record for the earliest day in the fall for a maximum temperature below 40F (11/15/1940 at 35F). High pressure will be centered near the MS/AL border at 12Z Friday, and low temperatures in the 28-32F range appear likely across the entire forecast area. A heavy frost is expected, especially across our western half, where winds should become calm. A warming trend is expected for Friday afternoon through Sunday with high pressure and dry conditions prevailing. A weakening front may arrive on Monday with limited moisture. No rainfall is expected, and temperatures should remain mild on Monday and Tuesday. 87/Grantham && .AVIATION... 00Z TAF Discussion. A deep cold core upper low over Arkansas was producing widespread low cigs across Mississippi and Alabama. The back edge of the rain has pushed into west Alabama, and the mostly light rain will end for areas west of I-65 by 02z and east of I-65 by 04z. Surface winds have become westerly at all TAF sites except KANB. KANB should become westerly by 02z. Strong cold air advection and cyclonic flow around the upper low will keep low cigs in across central Alabama through the overnight hours. However, relatively drier low level air will advect into the area from the west, and cigs will likely rise overnight, possibly above 1000 feet agl at most sites by 12z. The clouds will begin to clear across west Alabama by 18z, with sct conds at most sites between 18z and 21z. 58/rose && .FIRE WEATHER... Light to moderate rain will continue through tonight. ending from west to east after midnight. Cooler and drier air will move into the area for Thursday and Friday, but relative humidity values will remain above critical thresholds. Rain-free conditions continue through the weekend and at least the beginning of the work week. There are no fire weather concerns at this time. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 35 38 27 54 32 / 100 10 0 0 0 Anniston 35 38 28 55 34 / 100 10 0 0 0 Birmingham 32 38 29 56 36 / 90 10 0 0 0 Tuscaloosa 30 43 29 58 35 / 60 0 0 0 0 Calera 32 40 29 56 34 / 90 0 0 0 0 Auburn 37 42 31 55 37 / 100 10 0 0 0 Montgomery 34 44 30 58 36 / 90 0 0 0 0 Troy 35 44 30 57 34 / 100 0 0 0 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... Freeze Warning from 9 PM this evening to noon CST Thursday for the following counties: Autauga...Bibb...Blount...Chilton... Dallas...Fayette...Greene...Hale...Jefferson...Lamar...Lowndes... Marengo...Marion...Perry...Pickens...Shelby...St. Clair... Sumter...Tuscaloosa...Walker...Winston. && $$