562 FXUS64 KMOB 222101 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 401 PM CDT Tue Sep 22 2020 .NEAR TERM UPDATE /Now Through Wednesday/...Tropical Depression Beta has moved inland and continues to drift across southeast TX early this afternoon, while a strong surface ridge of high pressure continues to extend across the Appalachians, Tennessee Valley, and the adjacent southeastern U.S./northern Gulf Coast states. A plume of moisture continues to extend across our forecast area well to the east of Beta, resulting mainly broken to overcast low to mid level clouds, though a few places around the CWA have seen some breaks early this afternoon. Radar has been fairly quiet this afternoon, with only a few sprinkles or very light rain showers developing across parts of our area. Beta should remain a depression and is forecast to gradually lift northeast across southeast TX tonight through Wednesday. The surface ridge of high pressure should gradually shift eastward and extend eastward from the Tennessee Valley to the western Atlantic by Wednesday afternoon. Surface winds should gradually turn more southeasterly across our forecast area during the day Wednesday, with low level warm advection bringing increased surface dewpoints in the upper 60s to lower 70s across southeast MS into southwest AL and the western FL panhandle late Wednesday morning into Wednesday afternoon. In terms of the rainfall forecast, expect a fairly quiet night tonight with fairly limited coverage of showers over our region. The latest HRRR and WRF-ARW mainly hint at weak isentropic ascent near the immediate coast through the overnight period with mainly dry conditions inland. The deterministic guidance show a bit more in the way of isentropic ascent inland, particularly over southeast MS/southwest AL, so will keep a low (20-30%) chance of light rain showers in the forecast through the overnight period. A more pronounced southwesterly flow aloft develops over our region on Wednesday as the ridge axis shifts east and as an upper trough over east Texas shunts moisture associated with Beta into Louisiana and the MS Valley region. Weak shortwave impulses in the flow aloft and an increase in boundary layer moisture will support an increase in rain coverage, especially going into Wednesday afternoon. We have kept the highest POPs (likely) coverage over our southeast MS and adjacent southwest AL counties going into Wednesday afternoon. QPF amounts trended slightly lower through Wednesday afternoon over our western zones (0.25" to 0.50", maybe locally over 1"). Any limited flooding threat will probably be quite minimal over southeast MS considering the drier soil conditions and lower QPF, but we will still monitor given some uncertainty in the deep moisture placement (see below for additional comments on the flood threat Wednesday night into Thursday). Instability remains quite weak, but there be just enough for a slight chance of thunder in the region of highest moisture over southeast MS and adjacent southwest AL by Wednesday afternoon. Lows tonight range in the lower to mid 60s inland and in the upper 60s to around 70 near the immediate coast. Highs on Wednesday should reach into the mid 70s to around 80 degrees. A HIGH risk of rip currents continues along area beaches through the remainder of the week. /21 && .SHORT TERM /Wednesday night Through Friday night/...A warmer and more unstable airmass will begin to move into the area Wednesday into Thursday as what's left of Beta move northeast into north Alabama by Thursday afternoon. This will drag a warm front northward during the morning and north of the area by late morning and early afternoon. The focus of the heavier rainfall is expected to be along and north of the warm front from central Mississippi into northern Alabama. As a result rainfall amounts have been adjusted downward, however total rainfall amounts of 1 to 2 inches cannot be ruled out through Thursday night. This could still result in some minor flooding especially in areas that remain saturated from previous rains from Sally. Therefore a limited threat of flooding will remain in place across the area Wednesday night into Thursday. While instability values will increase especially near the coast on Thursday, wind fields will be weakening with time and the threat of any strong storms is expected to remain low. An upper trough slides east on Friday finally sweeping the remains of Beta well to the northeast with a lingering trough axis extending into southern Texas. This will maintain scattered to numerous showers and thunderstorms during the day on Friday with decreasing chances in the afternoon as some drier air works in from the northwest. Highs on Thursday will be in the upper 70s and low 80s with low to mid 80s expected on Friday. A high risk of rip currents continues along area beaches through the period. /13 && .EXTENDED TERM /Saturday Through Tuesday/...The base of the upper trough pinches off over Texas on Saturday and drifts southward as the main part of the trough moves off the east coast. This will push the deep layer moisture to the east of the area by late in the weekend. Early next week a much stronger trough is forecast to dig across the eastern states through midweek. This will send a strong cold front southward across the area late in the period, potentially delivering the first true taste of fall weather by the middle of next week. /13 && .MARINE...A pressure gradient between a strong surface ridge of high pressure building from the New England states to the northern Gulf of Mexico and Tropical Storm Beta approaching the central Texas coast will continue to result in moderate to strong easterly to northeasterly winds over the marine area through tonight. Winds turn more southeasterly to southerly Wednesday and Thursday. Seas remain elevated 4-6 feet through Thursday. && .MOB WATCHES/WARNINGS/ADVISORIES... AL...High Rip Current Risk through late Thursday night for ALZ265-266. FL...High Rip Current Risk through late Thursday night for FLZ202-204- 206. MS...None. GM...Small Craft Advisory until 10 PM CDT Wednesday for GMZ655-675. Small Craft Advisory until 4 AM CDT Thursday for GMZ650-670. && $$ This product is also available on the web at: http://weather.gov/mob