798 FXUS64 KBMX 231727 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1227 PM CDT Mon Sep 23 2019 .UPDATE... For 18Z Aviation. && .SHORT TERM... /Updated at 0347 AM CDT Mon Sep 23 2019/ Through Tonight. A shortwave trough is sliding east across the Great Lakes to the Northeast. At the same time the ridge has elongated and will flatten a touch of Central Alabama. This combined with the mid-level flow becoming northwesterly, will allow a cold front to move towards the Tennessee Valley by afternoon. A narrow, moist axis will work into the area ahead/along the front and could allow isolated to scattered showers to develop across the northern third of the area. Despite high forecast PWATs, forcing will be weak with warm temperatures aloft, limiting the instability and keeping thunder limited to just the far northwest. Really do not see much of a difference between the rain chances at 4 pm compared to 7 pm, other than the loss of daytime heating. With that in mind will keep the scattered activity through 10 pm, before decreasing coverage through Midnight as the front approaches the I-59 corridor. Elsewhere, rain- free conditions will continue with pre- frontal westerly flow causing temperatures to warm well into the lower 90s. Lows will be a touch warmer than previous nights as the added moisture and clouds will keep the temperatures in the upper 60s to low 70s. 16 .LONG TERM... /Updated at 0347 AM CDT Mon Sep 23 2019/ Tuesday through Sunday. Westerly flow aloft will continue Tuesday/Wednesday as a trough amplifies over central Canada and the north-central CONUS, a cutoff low spins over the northern Baja, and ridging temporarily becomes suppressed over the Gulf. The cold front and associated moisture axis will continue to sink southward across the southern half of the area, serving as a potential focus for shower and thunderstorm activity. But warm and dry air aloft combined with anticyclonic flow aloft should keep coverage isolated to widely scattered at best. Highs will range from the upper 80s to around 90F north to the low to mid 90s south. Will continue to side with the coolest guidance for Tuesday night across the northern half of the area given calm winds and low post-frontal dew points along with drought conditions. So most of the cooler spots will see lows in the 50s similar to the past couple of days. The front will begin to lift back to the northeast Wednesday ahead of a Canadian low pressure system with a trailing cold front extending back to the Central Plains. The GFS appears to be too aggressive with moisture advection from the west on Wednesday, and will go with the model consensus moisture forecasts which just barely support slight chance PoPs in the far west Wednesday afternoon as a few weak waves move through in the westerly flow aloft. Deep layer westerly flow will signal the beginning of the next heat wave. Current thinking is that convection that develops along the cold front should dissipate entirely before reaching our northwest counties late Wednesday night, but will continue to monitor. The cold front should stall out north of the area as it becomes parallel to the westerly flow and additional waves of low pressure develop over the Plains. Moisture levels may be trending upward slightly for Thursday/Friday afternoon, but chances of an isolated shower/storm are only around 10 percent for now, mainly for orographic effects in the northeast counties. The warming trend continues with highs in the mid to upper 90s. Record highs will be in jeopardy; see the climate section for more details. There will be a little bit of humidity with southerly winds developing by Friday, allowing heat indices to approach 100F in the southern counties. Amplified western trough/eastern ridge pattern is still on track to be in place for the weekend. Anomalous 595 decameter heights at 500 mb and ongoing drought will continue to support potential for record highs. Only limiting factor will be the potential for easterly flow to develop across our eastern counties by Sunday depending on the exact placement of the low and mid-level ridges. 32/Davis && .AVIATION... 18Z TAF Discussion. A weak cool front will push thru central Alabama overnight and stall out near the I-85 corridor on Tuesday. Scattered showers and a few tstms will spread across areas north of I-59 between 21z and 03z, but probably not make it far enough south to impact northern TAF sites. The air mass is relatively dry across central Alabama which will cause the pcpn to erode as it pushes southward. Sct-bkn clouds with bases arnd 6k ft agl will increase in areal coverage and lower slightly overnight, but stay above 3000 feet agl. 58/rose && .FIRE WEATHER... A cold front will bring isolated to scattered showers and thunderstorms to northwestern portions of Central Alabama this afternoon and evening, and southern portions of Central Alabama Tuesday afternoon. Afternoon relative humidity values will drop into the 30-35 percent range in southeast Central Alabama this afternoon and in far northern portions of Central Alabama Tuesday afternoon. These low humidity values and high KBDI values will result in continued elevated fire danger, but with light winds red flag conditions are not expected. && .CLIMATE... Record high temperatures: Thursday 9/26: Birmingham: 95 (1897) Montgomery: 94 (2016, 1984, 1954) Tuscaloosa: 97 (1955) Anniston: 97 (1931) Friday 9/27: Birmingham: 94 (1998, 1898, 1897) Montgomery: 96 (1954) Tuscaloosa: 97 (1954) Anniston: 97 (1954) Saturday 9/28: Birmingham: 94 (1986, 1911, 1904) Montgomery: 96 (1986) Tuscaloosa: 96 (1986, 1954) Anniston: 95 (1954) Sunday 9/29: Birmingham: 96 (1904) Montgomery: 96 (1904) Tuscaloosa: 96 (1986) Anniston: 95 (1904) && .PRELIMINARY POINT TEMPS/POPS... Gadsden 67 89 58 92 65 / 20 10 0 10 10 Anniston 68 90 60 93 66 / 10 10 0 10 10 Birmingham 70 90 62 93 69 / 20 10 10 10 10 Tuscaloosa 71 91 64 93 70 / 20 10 10 10 10 Calera 69 91 62 94 68 / 10 10 10 10 10 Auburn 69 90 64 92 67 / 10 20 10 0 0 Montgomery 70 95 66 96 68 / 10 20 10 10 10 Troy 67 94 65 94 67 / 10 20 10 10 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$