Area Forecast Discussion
Issued by NWS Birmingham, AL

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200 FXUS64 KBMX 191834 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 134 PM CDT Mon Apr 19 2021 .UPDATE... Midday Update and 18Z Aviation. && .SHORT TERM... /Updated at 0120 PM CDT Mon Apr 19 2021/ Through Tuesday. Very pleasant weather is ongoing across much of the Southeastern US this afternoon with dry and cool northerly surface flow. The air mass that has advected southward is a bit cooler than expected and temps are actually lower than they were yesterday at this time, despite full sunshine. I`ve reduced highs a bit for this afternoon as a result of the cooler air mass, but certainly not a significant change. Upper 60s to lower 70s should be widespread by later this afternoon. Tranquil conditions will continue through the day on Tuesday and temperatures will modify. An upper level shortwave will move to our south during the day, but still expecting too much dry air in the lower levels to produce any rainfall with this feature. High clouds should be the only weather to mention as the shortwave quickly moves off to the east by Tuesday afternoon with mild afternoon temps. 56/GDG .LONG TERM... /Updated at 0330 AM CDT Mon Apr 19 2021/ Tuesday night through Sunday. Broad troughing will rotate across the eastern CONUS Tuesday night while an elongated surface low tracks from the Ohio Valley to the Northeast with a cold front extending into the Lower MS Valley. Deep- layer winds will remain westerly due to the strong positive tilt of the trough, so moisture does not rebound sufficiently ahead of the front as it passes through the area early Wednesday morning. There will be a deck of low to mid-level clouds along the boundary, but most of the area should remain dry with cool air returning behind the front. Skies will clear during the afternoon with highs in the lower 60s north to lower 70s south. A chilly start is expected Thursday morning as a surface ridge builds over the Deep South. Conditions will be favorable for patchy frost generally north of I-20 where temperatures could fall as low as 34-36 degrees and even colder in localized areas. The surface ridge will shift towards the east coast on Friday, and low-level winds will become southerly between the ridge and a deepening shortwave trough over the Central CONUS. Moisture advection will overspread the area ahead of a surface low which will move into the ArkLaMiss Friday night then track across the Tennessee Valley on Saturday. Guidance is in better agreement regarding the evolution and ejection of this system, but there are still some small differences that appear to be improving with each model run. The rain should remain west of the area on Friday, but widespread showers and thunderstorms will spread across the area on Saturday, some heavy at times. This activity will collocate with a 50 kt low-level jet with progged eff. bulk shear values as high as 70 kts indicating potential for organized, sustained updrafts. However, there remains plenty of uncertainty regarding the efficacy of the thermodynamic environment as elevated thunderstorms look to be ongoing quite early in the morning as a warm front lifts northward from the Gulf coast. This early morning activity could hamper inland destabilization during the afternoon once the cold front moves into the area, especially if the surface low were to track closer to the coast which would prevent a sufficient warm sector from establishing far enough north. These uncertainties preclude me from introducing a severe threat into the forecast at this time. Won`t see much of a cool down behind the system as a subtropical ridge builds into the Southeast. Temperatures begin trending upwards heading into next week. 86 && .AVIATION... 18Z TAF Discussion. VFR conditions can be expected through the forecast period with clear skies and light northwesterly surface winds in the short term. Only high clouds can be expected during the morning on Wednesday with no restrictions. Surface winds will try to shift around to southerly by Tuesday afternoon, but remain very light. 56/GDG && .FIRE WEATHER... Rain free conditions through Friday. Light northwest surface winds will prevail today with minimum RH values 30 to 35 percent. Surface winds will become light southwest on Tuesday as a strong cold front approaches Alabama. Much cooler and drier Wednesday and Thursday with patchy frost possible Thursday morning. RH values Thursday afternoon could fall into the 25-30 percent range. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 45 75 42 59 35 / 0 0 10 0 0 Anniston 47 76 46 61 36 / 0 0 10 0 0 Birmingham 51 76 45 61 38 / 0 0 10 0 0 Tuscaloosa 49 76 44 62 38 / 0 0 10 0 0 Calera 50 75 46 61 38 / 0 0 10 0 0 Auburn 51 74 51 64 40 / 0 0 10 0 0 Montgomery 52 77 50 67 40 / 0 0 10 0 0 Troy 52 78 53 69 39 / 0 0 10 0 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$

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