627 FXUS64 KBMX 251721 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1221 PM CDT Sun Aug 25 2019 .UPDATE... For 18Z Aviation. && .SHORT TERM... /Updated at 0342 AM CDT Sun Aug 25 2019/ Today and Tonight. The active weather pattern continues today and tonight across Central AL. A weak frontal boundary is currently stretched through our south-central counties and has been helping generate some isolated to scattered shower activity early this morning. I would expect this to continue through much of the morning hours. To our northeast, we have a backdoor cold front moving through Northern Georgia, denoted by the low 60s dewpoints and mid 60s temps. It's not much of a frontal boundary, but is expected to move westward into eastern and northeastern Central AL by the early afternoon. To our northwest, we have a trough deepening into the Mid- MS Valley, which will lead to height falls across our area. This should help slightly enhance convection along the stalled frontal boundary, and along with daytime heating and the backdoor front, will generate more widespread showers and thunderstorms. The best chances will be generally west of I-65 where there will be more abundant moisture. The drier, easterly flow could help limit thunderstorm coverage in our far eastern counties this afternoon, but I still think there's a chance for some activity, so I'll leave roughly 50% PoPs in the forecast for those areas. PWATs remain on the upper end of climatology (97.5th percentile for this time of year), so we should see very efficient rainfall with these storms again today. If any develop and remain stationary over urban areas, or locations with poor drainage, we could once again see flooding impacts. I'll hold off mentioning any flooding concerns in the HWO for now because of the low confidence in whether the storms will set up over urban areas or over rural areas, where vegetation would mitigate the flood impacts. Meanwhile, an area of convection in the western portions of the Gulf of Mexico has developed a weak surface low. As the trough dips into the Mid-MS Valley this afternoon, the surface low gets picked up and lifted northeastward. It is expected to move through MS and approach our western counties late this evening into the overnight hours. PWATS begin to increase from the 2.00" that we've seen the past couple of days to 2.30"+, which would be near the max climatology for this time of year. Therefore, rain chances likely won't diminish much after sunset like we typically see in a summer pattern. Instead, showers and thunderstorms should continue for much of the area through the overnight hours. Instability increases quite a bit during the afternoon today, especially west of I-65, where values could 2000-3000+ J/kg. This could produce some stronger storms capable of gusty winds that could bring down trees. With the dry weather we've had so far this summer, we could see some weakened trees being brought down with sub-severe winds. 25/Owen .LONG TERM... /Updated at 0342 AM CDT Sun Aug 25 2019/ Monday through Saturday. On Monday, widespread showers and storms continue as an upper-level trough moves across the forecast area. At the surface, an area of low surface pressure is expected to track northeast through southern Mississippi and ultimately make its way through portions of western Alabama. This disturbance, arriving from the Gulf coast, will drive southerly winds across the region which will advect a very tropical- like airmass into Central Alabama. PWATs may rise to as high as 2.2 to 2.3 inches such that heavy downpours may lead to continued flooding issues in poor drainage and urban areas. Severe weather is currently not expected on Monday since instability will have a difficult time increasing within a rain-cooled airmass, but we will need to monitor for any enhancements in low-level helicity as the surface low moves across. More thunderstorms are expected on Tuesday as a cold front approaches from the northwest, but should see a bit of dry air work in behind the shortwave trough from Monday with shortwave ridging also noted in the low-levels which will help reduce the overall rain coverage. Temperatures are forecast to remain below 90F on Monday with highs in the low/mid 80s and upper 80s on Tuesday as widespread rain and cloud cover keeps us a bit cooler although humid. A northeast-southwest oriented cold front, associated with broad deep-layer troughing over Ontario, will pass through Central Alabama late Tuesday afternoon into Wednesday. As noted above, the presence of drier mid-level air from 700-500mb ahead of the front may hinder the spatial development of rain during the overnight hours. However, latest guidance diverges a bit on the timing of the frontal passage and amount of dry mid-level air. Therefore, decided to keep PoPs around 20-40 percent for Wednesday due to the lower confidence with highest chances along and southeast of I-20. A much drier airmass sets in behind the front for Thursday through Saturday with ridging amplifying back over the Southeast. May see a small increase in rain chances for our southeastern counties on Saturday as a low-level inverted trough develops over the Gulf Coast, but confidence on this solution remains low at this time. Therefore, plentiful sunshine is expected for the end of the work week with highs in the upper 80s/low 90s and overnight lows in the mid/upper 60s. 86 && .AVIATION... 18Z TAF Discussion. Persistent cloud cover will continue over most sites with exception at TCL/MGM/TOI. TSRA potential will be greatest at TCL/EET/MGM/TOI with best timing from 25/21z through 26/01z. Non- zero risk elsewhere but confidence too low to include in this issuance. Easterly low-level flow is well established across the eastern sites with more of a Southeast influence across central and western terminals. SHRA potential will persist after sunset through much of the evening hours. 05 && .FIRE WEATHER... Shower and thunderstorm chances remain elevated through Tuesday as we remain in a moist tropical airmass. With the increased moisture, minimum relative humidity values will be elevated as well. Gusty winds will be possible in close proximity to any thunderstorms that do develop. A surface frontal boundary is expected to move through Wednesday into Thursday. Although drier air will arrive, minimum relative humidity values for the end of the week should still remain above critical levels. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 68 81 69 87 69 / 70 80 60 60 40 Anniston 69 82 70 86 71 / 60 80 60 60 40 Birmingham 71 84 72 89 72 / 70 80 60 70 40 Tuscaloosa 71 84 73 90 73 / 70 80 40 70 40 Calera 69 83 71 89 71 / 70 80 60 60 40 Auburn 70 82 71 86 72 / 60 80 60 70 30 Montgomery 71 85 73 90 73 / 70 80 50 70 30 Troy 70 84 71 88 71 / 70 80 50 70 30 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$