608 FXUS64 KBMX 260506 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1206 AM CDT Thu Apr 26 2018 .UPDATE... Aviation Discussion. && .SHORT TERM... Through Thursday. Those pesky low clouds have finally cleared for areas along and west of I-65. The remaining clouds over east Alabama will clear out by sunset. On its heels are high clouds associated with a quickly evolving storm system over the Southern Plains States. Rain will likely reach northwest Alabama late this evening and spread into west Alabama by 3 am. Expect the rain to reach the I-65 corridor just before sunrise. Despite stable near surface conditions, moderate mid level lapse rates and strong forcing could produce some embedded thunderstorms in the rain shield, mainly for areas west of I-65. This is a quick moving system, and the leading edge of the heavier rain band will be near the Alabama and Georgia state line by late morning. A dry slot on the back edge of the rain shield will likely bring some clearing of the cloud cover across the southern counties Thursday afternoon, but deeper moisture associated with the upper low will keep skies mostly cloudy across north Alabama. The center of the 500mb low will track across north Alabama Thursday afternoon. Models show temperatures near -20C near the center of the upper low. This will produce a band of moderate instability across east Alabama in the afternoon. However, bulk shear values will be deceasing in the afternoon and forcing will be limited. 1000-850mb flow will also be unidirectional, so air mass will not be very supportive for parcel ascent to produce updrafts for robust storms. For now will not mention any severe text in the HWO. 58/rose .LONG TERM... Thursday Night through Wednesday. The surface low and associated cold front will slide off to our east fairly quickly, and by Friday morning, rain chances across Central AL look limited as dry air moves in behind the departing low. Surface high pressure builds in over the weekend as an upper level ridge slides over the eastern half of the CONUS. This will in a warming trend for our afternoon highs over the weekend with mostly clear skies. The first half of the next week looks to follow a similar trend as the weekend. Synoptic scale ridging persists over the Eastern CONUS as a trough digs into the Pacific NW and into the Great Basin by Monday evening. The high pressure over the Southeast US blocks the trough to our west through at least mid-week, resulting in warm and dry weather. 25/Owen && .AVIATION... 06Z TAF Discussion. Rain and possibly thunderstorms will spread into Central Alabama late overnight. Expect reductions in vis and cigs to MVFR, and possible brief periods of IFR, with this activity. Will need to watch for light fog ahead of the rain at MGM and TOI, but for now have not included reduce vis for that area. Boundary layer winds will gradually increase through the remainder of the night, which should prevent widespread fog. Behind an area of more persistent rain, showers are likely to continue through the day tomorrow, with cigs slowly rising. However, do not anticipate any cig heights above 3kft through the day tomorrow. Winds will be the most problematic part of the forecast, as the surface low with this system will move across the area. Generally, winds will be light and variable to begin the forecast period, and gradually shift to the southeast ahead of the approaching low, and as rainfall arrives from west to east. Winds will increase and gradually turn to the south and then west as the rainfall ends. Due to a tightened pressure gradient, wind gusts up to 20kts are possible Thursday afternoon. No amendments are scheduled for KASN due to unreliable wind data being reported at that site over the past few days. 14 && .FIRE WEATHER... A break in rain chances will occur during the day today. A cold front moving through late tonight and Thursday will then bring wetting rains. Afternoon minimum relative humidity values will remain above 50 percent through Thursday. There are no fire weather concerns at this time. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 52 64 48 70 46 / 50 90 20 10 0 Anniston 54 66 49 72 47 / 30 90 20 10 0 Birmingham 55 67 50 72 49 / 50 90 10 10 0 Tuscaloosa 56 68 50 72 49 / 80 90 10 10 0 Calera 56 67 49 71 48 / 50 90 10 10 0 Auburn 54 69 51 71 50 / 10 80 20 10 10 Montgomery 56 72 51 73 50 / 20 80 10 10 0 Troy 55 73 52 73 51 / 10 70 10 10 10 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$