070 FXUS64 KBMX 042325 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 625 PM CDT Sun Oct 4 2020 .UPDATE... For 00Z Aviation. && .SHORT TERM... /Updated at 1241 PM CDT Sun Oct 04 2020/ Analysis. A longwave trough remains over the Ohio River Valley region aloft while deep-layer ridging is building over the Desert Southwest. In the lower levels, ridging is now displayed to our east while ridging was analyzed over the Central Plains. A surface cold front was analyzed from near Nashville, TN to just west of Tupelo, MS and further southwest into Northern Louisiana. The airmass remains fairly dry across the area with the 04/12z BMX sounding only containing a precipitable water value of just over 0.80 inches. Forecast. Expect the upper pattern to begin to shift later today as a longwave ridge propagate east in the amplified flow. This will help force the longwave trough to prograde eastward with time as deep- layer ridging expands over the Desert Southwest Region. Most modeling suggests precipitable water values increasing to near 1 inch across the west and southwest with values otherwise in the 0.85-0.90 range in the vicinity of the front as it moves southeast across the area. Expect a gradual increase in mainly high level clouds this afternoon and overnight as the front nears from the northwest and moves across the area. The airmass remains too dry for precipitation in the low to mid levels. Today. Expect mostly sunny skies north early this afternoon, followed by partly cloudy skies late this afternoon and into the evening north. Partly cloudy skies will persist across the southern and central counties as clouds stream northeast over the Gulf of Mexico from Tropical Storm Gamma. Highs will range from the mid 70s north and east to near 80 southwest. Winds will shift out of the northwest 6-12 mph later this afternoon northwest with the frontal passage with speeds decreasing 4-8 mph this evening. Tonight. Look for partly cloudy skies as the front continues moving southeast across the area. The front is expected to begin to decelerate overnight and will gradually become more diffuse with time. Lows will be cooler northwest with lows in the mid to upper 40s generally northwest of Interstate 59. The rest of the forecast area will experience lows in the low to mid 50s elsewhere. Winds will become northwest with the frontal passage 3-6 mph overnight. Monday. Expect mostly sunny skies north with partly cloudy skies south on Monday. Highs will range from the low to mid 70s generally north of the Interstate 20 corridor while readings will reach to around 80 along and south of the Interstate 85 corridor. Winds will be out of the northeast 5-10 mph. 05 .LONG TERM... /Updated at 0152 PM CDT Sun Oct 04 2020/ Made some changes to the later portion of the extended forecast with guidance continuing to trend on the wetter side in advance of the tropical disturbance currently south of Jamaica. The NHC is forecasting the disturbance to become a tropical depression in the next day or two as it moves towards the northwestern Caribbean Sea. Made some small raises to PoPs Friday through Saturday since we may begin to see the reintroduction of tropical moisture into the area as the disturbance moves into the Gulf, but still did not go as high as some guidance suggests due to the model spread and uncertainty. This will be the feature to watch through this next week, however, since Tropical Storm Gamma will move towards Mexico and have no impact on the eastern Gulf Coast region while most of Central AL stays in the dry airmass through at least mid week. 86 Previous long-term discussion: /Updated at 0349 AM CDT Sun Oct 04 2020/ Tuesday through Saturday. Moisture associated with Tropical Storm Gamma is expected to be slowly drawn northward on Tuesday due to a ridge near Bermuda and a shortwave trough moving through the Ohio Valley. For now it appears the northern edge of this moisture and the possibility for showers may stay just south of our coverage area. A warm day is expected with highs mainly in the lower 80s. The moisture gradient to our south is expected to remain in place near the Gulf Coast for Wednesday and Thursday. High 500 mb heights will promote warm and dry conditions across our area. A shift in the forecast appears to be taking shape for Friday and Saturday. There is good agreement for an unsettled pattern across the Gulf of Mexico and the potential for additional tropical development. At the same time, a shortwave is expected to move eastward from Texas. This should result in the northward movement of the disturbance or potential tropical cyclone. Placement of the heaviest rain and high rain chances is uncertain, but rain chances should increase in the Friday to Saturday period. 87/Grantham && .AVIATION... 00Z TAF Discussion. VFR and rain-free conditions are expected for the next 24 hours and beyond with light northerly winds as a weak cold front moves through. Very high clouds continue to stream across the area originating from Tropical Storm Gamma near the Yucatan Peninsula. 32/Davis && .FIRE WEATHER... Dry weather and light northeast winds will persist through Monday. Minimum RHs will be in the 35-45 percent range. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 49 75 50 80 53 / 0 0 0 10 0 Anniston 51 77 53 80 56 / 0 0 0 10 0 Birmingham 52 78 54 82 57 / 0 0 0 10 0 Tuscaloosa 53 79 53 83 57 / 0 0 0 10 0 Calera 53 78 54 81 58 / 0 0 0 10 0 Auburn 54 78 57 77 61 / 0 0 10 10 0 Montgomery 54 81 58 81 61 / 0 0 10 10 10 Troy 53 79 59 77 62 / 0 0 10 20 10 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$