Area Forecast Discussion
Issued by NWS Birmingham, AL
Issued by NWS Birmingham, AL
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300 FXUS64 KBMX 260846 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 346 AM CDT Wed Jun 26 2024 ...New LONG TERM... .SHORT TERM... (Today through Thursday) Issued at 158 AM CDT WED JUN 26 2024 Key messages: - Rain chances will return today, along with the opportunity for strong to severe storms across the western half of Central Alabama this afternoon through the early evening hours. Gusty downburst-type winds will be the main hazard. - Very hot temperatures will moderate, at least temporarily through Thursday returning closer to normal. Following the blast furnace of Tuesday in which several locations hit the 100 degree mark, we`ll start to trim back on high temperatures over the next couple of days. We`ll even add in some rain chances into the mix (which we greatly need) but we`ll have to keep an eye out for a few strong to severe storms across roughly the western half of Central Alabama during the afternoon and early evening hours today. Looking out the window this morning, the most notable feature present is the MCS across the bootheel of Missouri moving southward into western Tennessee. As expected, this feature will continue moving southward and eventually decay as it approaches northern Alabama. Outflow boundaries are expected to move southward out ahead of the old MCS and will be an additional trigger for storm development later today. 500mb flow has shifted toward the northwest as the ridge builds over the desert southwest. An upper level shortwave will dive southward today and provide synoptic lift, coupled with decent shear aloft and strong instability at the surface. There`s a good chance that another MCS will develop somewhere in the vicinity of eastern Arkansas and northern Mississippi this afternoon. If an MCS doesn`t fully develop, we`ll at least see scattered to numerous storms which may become more organized clusters through the late afternoon and early evening hours. Best available moisture coupled with strong surface heating will exist across the western half of Central Alabama, especially across the far western counties. Some of the CAMs are suggesting the possibility of temperatures warming into the mid to upper 90s before storms start to develop, producing SBCAPE values between 3000 and 4000 J/kg. With dry air aloft, DCAPE values will be 1000+ J/kg. Microburst/downburst ingredients appear sufficient for severe wind gusts with just enough effective northwesterly shear to keep updrafts sustained longer. The farther east you go, the more dry air will be present, especially from the surface to 700mb. Although a few strong storms will certainly be possible along and east of I-65, severe chances will be reduced, along with overall coverage of showers and storms. Highs today will remain very hot, but about a degree or two "cooler" than yesterday, topping out in the upper 90s to near 100 degrees before storms develop during the afternoon. Storms are expected to push southward through the evening hours, with high-res guidance now indicating that most activity will diminish through the overnight hours. A stray shower or storm can`t be ruled out as a surface front slowly moves southward into Tennessee and northern Mississippi, but trends are much drier. As the 500mb trough axis continues to move slowly southward on Thursday, drier air will begin to advect into the region from the north, which will help to suppress rain chances to the south. More numerous showers and storms are possible across the U.S. 80/I-85 corridors with isolated to scattered convection across the north. We`ll turn the thermostat down on the blast furnace, as widespread clouds will initially keep temperatures cooler Thursday morning before mixing out during the afternoon. Highs will top out in the lower 90s Thursday afternoon with light northerly surface flow. 56/GDG && .LONG TERM... (Thursday night through next Tuesday) Issued at 346 AM CDT WED JUN 26 2024 - Hot and increasingly humid conditions are expected this weekend into next week, with heat indices at or above 105 degrees at times, especially Sunday. Scattered showers and storms will also be possible each afternoon. Subtropical ridging will continue to build eastward into northern Alabama Friday, while a weakness in the ridge will remain along the Gulf Coast and up into Central Georgia. Weak low-level flow will become southwesterly, helping maintain lower 70s dew points. PWATs look to range from around 1.6 inches in West Alabama to near 2 inches in East Alabama. Scattered showers and storms are expected to develop with daytime heating, with the highest chances in East Alabama where the best moisture will be and near the weakness in the ridge, and near possible remnants of an MCV. Updraft intensity should be muted by warm mid-level temperatures (500mb temps near -2C) which may limit lightning activity. Guidance has trended slightly lower on highs with the ridge not building in as quick, so heat indices look to remain less than 105 degrees. Subtropical ridging strengthens to around 596 decameters on Saturday. Despite the strength of the ridge, PWATs at or above 2 inches should still allow for some scattered showers and (weak) storms to develop, highest chances once again east. With the moisture, guidance has trended slightly less hot, but with elevated dew points a few spots could see heat indices approaching 105 depending on the competing factors of increasing Gulf moisture and dry ground conditions. Meanwhile a shortwave moving through the Great Lakes will cause a cold front to sink southward into Tennessee on Sunday. Slight height falls occur over Central Alabama as the ridge retrogrades a bit westward. Higher dew points pooling south of the boundary will result in the potential for heat indices to reach 105 degrees across much of Central Alabama depending on how quickly convection initiates in the tropical-like air mass. Latest guidance is suggesting the lower dew points with the front may slip southward into our northern counties Monday and Tuesday. This would result in some reduced rain chances in the north, with a less humid but still hot air mass. Meanwhile, enhanced dew points along and south of the boundary will result in the potential for heat indices in the 105-110 range. Exact placement of this boundary is subject to change, though. Meanwhile, the ridge looks to build back to the east Tuesday resulting in increasing temperatures as we go through the holiday week. 32/Davis && .AVIATION... (06Z TAFS) Issued at 158 AM CDT WED JUN 26 2024 VFR conditions will continue through much of the forecast period. SHRA/TSRA development will be possible across western Alabama today, expected to affect KTCL with a potential for prevailing TSRA between 18z and 00z this afternoon and into the evening. Storm chances are less at BHM and EET, but still warrants the inclusion of PROB30 during that timeframe. Storms will be capable of producing variably gusty downburst-type winds with rapid reduction of visibility due to heavy rains. Prevailing winds this afternoon will be from the west between 5 and 10 knots. Storms will diminish during the overnight hours with VFR conditions and generally calm winds. Looking into the planning period, MVFR or IFR stratus may begin to develop after 06z Thursday morning. That may be included in subsequent TAF cycles. 56/GDG && .FIRE WEATHER... Moisture and chances for showers and storms increase across West Alabama today, while RH values in East Alabama will still drop into the 25 to 35 percent range. Scattered, mainly afternoon and evening showers and storms are expected Thursday into the weekend, with the highest coverage in the southeast. RH values will stay above 45 percent in most areas. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 99 69 93 70 / 30 40 40 10 Anniston 98 71 93 72 / 30 30 40 10 Birmingham 99 73 93 73 / 40 30 40 10 Tuscaloosa 97 72 93 73 / 60 40 40 10 Calera 99 73 94 73 / 40 30 40 10 Auburn 97 73 91 72 / 20 20 50 20 Montgomery 98 73 93 73 / 40 40 60 20 Troy 98 71 93 71 / 40 40 60 30 && .BMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...56 LONG TERM....32/Davis AVIATION...56