Area Forecast Discussion
Issued by NWS Birmingham, AL
Issued by NWS Birmingham, AL
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541 FXUS64 KBMX 071136 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 636 AM CDT Tue May 7 2024 ...New AVIATION... .SHORT TERM... (Today through Wednesday) Issued at 251 AM CDT TUE MAY 7 2024 Another warm day across Central Alabama as the main ridge remains to our east. With high pressure centered over the Atlantic, southerly flow will continue to pump moisture into the lower levels. Meanwhile a cold front will begin to advance eastward through the day and into the evening hours. With the tightening pressure fields, the added lift will allow for showers and storms to develop ahead of the front during the peak heating of the day. With the abundance of moisture in place and added instability, any storm that develops this afternoon will be strong to marginally severe. Will keep the severe mention for areas along and north of the I-59 corridor right now as the highest rain chances are in this area. However, any isolated storm south and east of this area will also need to be monitored, but the probabilities remain low in these areas. Highs today will be in the upper 80s to low 90s. The front never makes it into the area before it retreats back to the north as a warm front, awaiting the next shortwave in the extended period. With that said a MCS will likely develop this evening to our north along the front and slide southeast, clipping the northeast by sunrise. Look for activity to spread south and east through the morning, although it will be decaying as it spreads. A few strong storms will be possible in the morning, but we should see a lull in storms as the showers spread. By the afternoon, isolated to scattered showers and a few storms will be possible. Most of the storms in the north should be on the weaker side as the area will be a tad more stable that the south. Areas in the south will reach the low 90s by the afternoon, so any shower/storm that develops down here certainly will be strong. Right now it does not appear that there will be any organized severe weather during the daytime hours of Thursday. 16 && .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... (12Z TAFS) Issued at 630 AM CDT TUE MAY 7 2024 The MVFR ceilings will rise and become VFR by 15-17z. Scattered thunderstorms will be possible in the afternoon for the northern terminals. Starting off with a PROB30 mention. Winds will be south southwest 5-10 kts. Low clouds will build in again tonight and drop to MVFR/IFR by 8 to 10z. 16 && .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 86 67 88 68 / 40 50 50 60 Anniston 87 69 88 70 / 40 40 40 50 Birmingham 88 70 88 71 / 50 30 40 60 Tuscaloosa 87 70 89 72 / 50 30 20 50 Calera 87 69 88 71 / 50 30 30 40 Auburn 87 69 88 71 / 20 20 40 10 Montgomery 90 71 92 72 / 30 10 20 10 Troy 90 69 91 71 / 20 10 20 10 && .BMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...16 LONG TERM....32 AVIATION...16