Area Forecast Discussion
Issued by NWS Birmingham, AL
Issued by NWS Birmingham, AL
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257 FXUS64 KBMX 041755 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1255 PM CDT Sat May 4 2024 ...New SHORT TERM, AVIATION... .SHORT TERM... (This evening through Sunday) Issued at 1233 PM CDT SAT MAY 4 2024 High pressure over the Atlantic will keep weak southerly flow over the state with low level warm air and moisture advection present through the short term. Today, isolated showers and thunderstorms are possible in the afternoon across much of the area. Instabilities will be decent, though PW values will struggle to be at 90% for this time of year. A few storms could produce moderate showers, but overall coverage of activity should be low. Tonight, all activity is expected to weaken. Fog development is likely in the areas that receive rainfall this evening. However, visibilities and coverage will depend on the evening rainfall so will hold off on any confidence wording for now. Sunday, PW values are expected to increase through the afternoon with a greater coverage of diurnal showers and thunderstorms expected. Instabilities will be between 1500 and 2000 J/kg and there will be a small amount of shear present. By the evening, high res models show a feature moving into the state from the east. with a weak mid level jet. Coverage of activity is expected to increase through the late evening as more scattered showers and thunderstorms move into northwest Alabama. Temperatures will be several degrees above normal for high temperatures today and Sunday, with low temperatures several degrees above normal tonight. 24 && .LONG TERM... (Sunday night through next Friday) Issued at 322 AM CDT SAT MAY 4 2024 A weak southern stream shortwave currently along the Arizona/Mexico border will trigger considerable convection along the West Texas dry line today, eventually growing upscale into an MCS across Central Texas. The resulting MCV/shortwave trough will reach Alabama by Sunday evening, triggering scattered to numerous showers and storms with PWATs near 1.75 inches, though any heavier rainfall will be very isolated. Some of this activity may linger into Monday morning in the northeast counties. Depending on how quickly the shortwave exits to the east, subsidence may suppress convection across much of Central Alabama Monday afternoon or at least keep it isolated to widely scattered. This may warrant a decrease in PoPs in later updates. Another shortwave moves through Monday evening but will be much weaker as ridging builds over the eastern CONUS, with only slight chance PoPs in the forecast. Meanwhile a deep trough will be digging across the western CONUS and Plains with ridging building further east. A subtropical ridge will also be strengthening over the southwestern Gulf. Rising 500mb heights across Central Alabama will be a limiting factor for convection on Tuesday, though some guidance does indicate a pre- frontal moisture axis that could trigger isolated to widely scattered convection. Strengthening low-level southwesterly flow will result in warming temperatures. The mid-level ridge axis pushes east of the area Wednesday as the trough becomes positively tilted from Ontario towards the Four Corners, but mid-levels remain warm and fairly dry limiting convective development. Meanwhile a stalled out front just northwest of the Ozarks may begin to advance as a cold front Wednesday night in the wake of low pressure moving through the Ohio Valley. One or more MCSs will probably develop off to our northwest. Will have to keep an eye on them towards the overnight hours given increasing bulk shear, though they may remain just north of the area given westerly flow aloft and better height falls remaining north of the area. Mid-level troughing remains over the Midwest and Great Lakes Thursday while weakening further to the west. The ridge over Central Alabama will begin to flatten by Thursday night. A fairly strong cold front for May will begin to move in by Thursday night. A strong EML and associated steep mid-level lapse rates will result in a very unstable air mass south of the front with 0-6km bulk shear values around 50 kts. This will result in the potential for large hail and damaging winds with any storms or MCSs that develop. Limiting factors will be whether any leftover cold pools from Wednesday night`s MCS(s) limit destabilization, and a tendency for better forcing to remain north of Central Alabama. Still, will need to monitor the potential for severe storms and heavier rainfall as we get closer and the mesoscale details become clearer. Models vary regarding how quickly the front clears the area Friday, but it does look like we should see some pleasant spring weather by next weekend after we get through summer-like conditions the next few days. 32/Davis && .AVIATION... (18Z TAFS) Issued at 1233 PM CDT SAT MAY 4 2024 Isolated to scattered convection is possible this afternoon. Due to low confidence in coverage and timing of any activity over a TAF site, have left in VCSH for now, and will amend if needed. Tonight, activity should weaken, though there should be plenty of low level moisture for fog development. Have included MVFR visibilities for now, and will watch for areas of rainfall in the evening to better determine the best coverage for fog development. 24 && .FIRE WEATHER... Periods of showers and storms are forecast through Monday. Given the scattered nature of the activity, rain amounts will average near one-half inch, with higher amounts where thunderstorms track. With increasing moisture, minimum RH values will be above 40 percent each afternoon. 20-foot winds should average less than 10 mph from the south to southwest, though could gust to around 25 mph and be variable in direction in or near thunderstorms. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 61 86 63 84 / 30 30 60 50 Anniston 63 86 64 85 / 30 30 60 50 Birmingham 64 88 66 85 / 20 40 60 40 Tuscaloosa 64 88 66 86 / 20 40 60 30 Calera 64 86 66 85 / 20 40 50 40 Auburn 65 85 66 84 / 30 30 40 40 Montgomery 65 88 66 87 / 20 30 40 30 Troy 64 88 65 87 / 30 30 30 30 && .BMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...24 LONG TERM....32 AVIATION...24