Area Forecast Discussion
Issued by NWS Birmingham, AL
Issued by NWS Birmingham, AL
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974 FXUS64 KBMX 281721 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1221 PM CDT Sun Apr 28 2024 ...New AVIATION... .SHORT TERM... (Today through Monday) Issued at 246 AM CDT SUN APR 28 2024 One more day with high pressure in control of the area. Of course the center of the high pressure is off the coast of Virginia, so it will continue to lose its grip over the area. With that said and southerly flow, there should be just enough lift this afternoon to generate a shower/storm or two in the southwestern portions of the area. Highs will generally be in the low to mid 80s once again. Skies clear up some tonight, but the southerly flow continues, so low clouds will likely develop again overnight. On Monday, the front continues to slowly work its way east. By the afternoon, there should be an ongoing complex of storms to our west. This MCS should begin to accelerate in the afternoon and approach our western counties. Problem with the forecast is what will happen to the MCS? Could it hold its trajectory and slide through the southern half of the area, or will it pull out and then shift to the south of our area? Each scenario is plausible, so the confidence and placement of the best rain chances Monday afternoon is low. Ultimately the placement of the high pressure system to our west, weaknesses on the western edge of the high pressure, and amount of the rain in the resultant cold pool, will all play a part, so the mesoscale features will be really important as we approach this time frame. Typically this pattern results in more of a southern push with the cold pool and thus we would be cut off from the main action. As we see some more model runs we should get a better feel of the likely path. For now the best rain chances will be in the west by Monday afternoon, with the best potential for strong storms would be in the southwest. 16 && .LONG TERM... (Monday night through next Saturday) Issued at 310 AM CDT SUN APR 28 2024 A mid-level shortwave trough and associated sharp upper-level trough will move through Alabama Monday night into Tuesday morning, accompanied by an axis of PWATs around 1.6 inches. As mentioned above, there is uncertainty over whether an MCS will be over the area to start the period or if it will be southwest of the forecast area. If there is an MCS over the area it should weaken and eventually dissipate as it encounters a drier low-level air mass. With MLCAPE less than 1000 J/kg and 0-6km bulk shear only around 25-30kts, while some gusty winds will be possible the probability of severe storms is very low. Meanwhile, what may be a separate area of showers and storms will move across the northern counties Monday night due to forcing associated with the upper trough and the right entrance region of the upper-level streak. The uncertainties carry over into Tuesday regarding how quickly subsidence and dry northwesterly flow put an end to the rain chances. Overall the model consensus supports chance PoPs during the morning decreasing through the afternoon. Lingering clouds could take a couple of degrees off of the high temperatures. Ridging will build over the Gulf up the East Coast Wednesday and Thursday, downstream of a trough over the northern Rockies eventually reaching the Northern and Central Plains. A few weak convectively generated shortwaves move through in relatively weak westerly flow aloft while moisture attempts to move in from the west, but with the ridge PoPs remain only 10-20%. Temperatures warm into the upper 80s with some highs around 90 in the southeast counties. A cold front eventually approaches from the northwest Friday into Saturday, but models vary with how much progress it makes before stalling, depending on the amplitude of the trough moving through the north-central CONUS. Some increase in rain chances will occur as moisture increases ahead of the front. 32/Davis && .AVIATION... (18Z TAFS) Issued at 1214 PM CDT SUN APR 28 2024 Ongoing cumulus level cloudiness early in the period should mix out and up through the first 3-4 hours of the forecast, keeping conditions at VFR. Based on the latest computer model low level moisture projections, it appears there should be less cloud coverage tonight/Monday morning compared to last night/this morning. I went ahead and kept conditions VFR overnight based on this idea. If the strato-cumulus clouds do form tonight, I don`t foresee them getting much below 3000 ft (if even that low). Precipitation should hold off in our area until after 1800 UTC Monday. /61/ && .FIRE WEATHER... Southerly low level flow will keep afternoon RH values well above critical values. No wetting rain through Monday morning, with increasing rain chances across west Alabama late Monday afternoon into Monday night and again on Tuesday. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 58 84 60 80 / 0 10 70 50 Anniston 60 84 62 81 / 0 10 50 40 Birmingham 62 84 62 81 / 0 20 70 40 Tuscaloosa 62 84 62 83 / 10 40 70 40 Calera 61 83 63 81 / 0 20 60 40 Auburn 61 83 63 81 / 0 10 20 40 Montgomery 61 85 64 83 / 0 20 40 40 Troy 60 85 62 83 / 0 10 20 40 && .BMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...16 LONG TERM....32 AVIATION...61