Area Forecast Discussion
Issued by NWS Birmingham, AL
Issued by NWS Birmingham, AL
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619 FXUS64 KBMX 071831 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 131 PM CDT Tue May 7 2024 ...New SHORT TERM... .SHORT TERM... (This evening through Wednesday) Issued at 131 PM CDT TUE MAY 7 2024 This afternoon. The mid-level longwave ridge axis will move further to the east of the area this afternoon while a zonal flow aloft with some shortwave disturbances will move east over the area through the afternoon and evening hours. Surface high pressure is centered well offshore of the Southeast Atlantic Coast but is elongated and extends west across much of Florida. Expect shower activity to continue to develop across our western and central counties and expand east with time. Some of the showers may build into thunderstorms will be possible later this afternoon and into early evening if enough instability materializes. Winds will be from the southwest at 7-14 mph. High temperatures will range from the mid 80s far north and northeast to the low 90s far south. Tonight. A more southwest flow develops over the area tonight as longwave ridging moves further east over much of the Mid Atlantic and Southeast Coastal areas while a large upper low spins over the Western Dakotas. Surface high pressure will remain centered over the Southwest Atlantic Basin, but will continue to nose eastward toward the Wiregrass Region. A few weak shortwaves in the mid levels will continue to move east over the area, providing enough uplift for a continuation in shower and storm chances, though this will largely be concentrated across the northwest half of the area. Showers will remain the predominant element, but a few thunderstorms will remain possible. Some patchy fog may develop across portions of the south and southwest before daybreak. Winds will be from the south to southwest at 4-8 mph. Low temperatures will range from the upper 60s far east to the low 70s far southwest. Wednesday. The sprawling upper low will become centered over the South Dakota and Nebraska border on Wednesday while little change occurs at the surface with the forecast area remaining between high pressure to our southeast and lower pressure across Texas, extending northeast into the Midwest. Chances for showers and some thunderstorms will be greatest generally along and north of the Interstate 20 corridor with a scattered coverage, with isolated coverage expected across the northern half of the forecast area with isolated activity south. Winds will be from the south to southwest at 7-14 mph. Highs will range from the mid 80s in the higher terrain east to the low 90s across the southwest and far south. 05 && .LONG TERM... (Wednesday night through next Monday) Issued at 356 AM CDT TUE MAY 7 2024 A rex block over the western CONUS will be transitioning to an omega block across the Western CONUS and Eastern Pacific to start the period. Meanwhile a subtropical ridge will strengthen over the Bay of Campeche. The upper low over the Central Plains will break up into a couple pieces, with the strongest vort max moving east across the Midwest Wednesday night and getting absorbed into the trough over the Great Lakes by Thursday, while another piece retrogrades back to the southwest CONUS. A middle piece may linger across the Central Plains before digging southeastward across the Ozarks Thursday night. At the surface, a disorganized but sub-1000mb area of low pressure will move eastward across the Ohio Valley, while a cold front will sag southeastwards, eventually moving into Central Alabama on Thursday. Pre-frontal convection across the Mid-South is expected to grow upscale into an MCS or QLCS Wednesday evening. This will eventually move towards our northern counties late Wednesday evening or overnight. Southerly winds will help keep temperatures warm Wednesday night, so CAPE values should still be at or above 1000 J/kg as the MCS comes in, also aided by steep mid-level lapse rates associated with an EML. 50 to 60 kts of 0-6 km bulk shear will also aid storm organization. There continues to be a typical amount of spread in the guidance regarding timing. A quicker timing would have better instability and better dynamics, while veering low- level flow after midnight should result in some weakening with a later timing. Main threat looks to be damaging winds, with hail possible in any embedded strong updrafts. Will have to monitor any cells developing ahead of the MCS as shear profiles would be potentially supportive of tornadoes. However, this probability of development is too low to message at this time, and 0-3km shear vectors will be parallel to the MCS limiting tornado potential with the MCS itself. Will continue to monitor trends closely. The MCS or new storms developing along its outflow may continue to pose an isolated severe threat Thursday morning as a subtle shortwave moves through, though continued weakening/veering flow should keep it from restrengthening too much. A volatile air mass will remain in place Thursday afternoon with 3000+ J/kg of CAPE and 55 kts of 0-6km bulk shear as well as continued steep mid- level lapse rates. However, models show little in the way of activity during the afternoon as the front moves in. This is probably due to some subsidence in the wake of the subtle shortwave as 700-500mb flow becomes more anticyclonic and moisture also dries out in that layer. Additionally, veering winds will limit convergence along the front. Any storm that can remain sustained Thursday afternoon would quickly become severe with large hail and damaging winds, but currently expect that to be an isolated occurrence. Meanwhile, another subtle shortwave/mid- level speed max may trigger convection upstream over Mississippi and Louisiana. This could result in an MCS tracking across southern Alabama Thursday evening, potentially impacting some of our southern counties in an environment very favorable for damaging winds. However, some guidance keeps the bulk of the activity south of our area Thursday night. Bottom line is stay tuned to the latest forecasts for Wednesday night through Thursday night as changes will probably occur as the mesoscale details become more clear. Cooler, much less humid air will move in behind the front for the weekend. A clipper system will pass to our northeast Saturday, resulting in a secondary frontal passage Saturday night into Sunday, but rain chances remain 10 percent or less. 32/Davis && .AVIATION... (18Z TAFS) Issued at 1254 PM CDT TUE MAY 7 2024 Expect scattered to broken mid level clouds today with isolated showers and a few thunderstorms to develop through the afternoon and into the evening. Thunder potential is too low to include at any terminal but shower activity potential is high enough to include at all northern sites generally from 18 to 23z with lingering shower potential at most northern sites through 04z Wednesday morning. Chances for showers with a few thunderstorms will become great enough to mention toward 15z Wednesday late morning across the northern sites. Clouds will continue to increase tonight into Wednesday with some MVFR conditions overnight. Some reduction in visibility is possible across portions of the southern portion of the area before daybreak Wednesday. 05 && .FIRE WEATHER... Isolated to scattered showers and storms are possible each day through Wednesday, with greater rain chances Wednesday night and Thursday. Rainfall amounts will average 0.5-1.0 inch under heavier storms. Afternoon minimum RH values will be above 40-45 percent each afternoon through mid week. 20-foot winds will average less than 10 mph from the south to southwest today, increasing to 8-12 mph Wednesday. Wind gusts to around 25 mph are possible near convection. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 68 88 68 85 / 50 50 60 80 Anniston 68 87 70 86 / 40 50 50 80 Birmingham 70 89 71 87 / 50 40 60 80 Tuscaloosa 71 90 72 88 / 40 40 50 70 Calera 70 88 71 85 / 40 40 40 80 Auburn 68 87 71 85 / 20 30 10 70 Montgomery 70 91 72 88 / 20 20 10 60 Troy 69 90 71 88 / 10 20 10 50 && .BMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...05 LONG TERM....32 AVIATION...05