520 FXUS64 KBMX 100929 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 429 AM CDT Sat Oct 10 2020 .SHORT TERM... /Updated at 0427 AM CDT Sat Oct 10 2020/ Today and Tonight. Delta continues north-northeastward this morning and is generally centered near the ArkLaMiss and is forecast by the NHC to continue northeast into Central MS later today. As such, PoPs will be quite elevated for the majority of the short-term as both mesoscale and synoptic forcing mechanisms foster periods of shower and thunderstorm development near and downstream of the remnant circulation. This currently includes a linear band now underway near an axis of low-level confluence in southern MS. This is tracking northeastward at this time along with some gusty winds. Potential impacts for today are discussed below. * Severe Weather & Tornadoes: Due to the positioning of Delta and the presence of wedged easterly flow stemming from the Southern Appalachians & East Coast, Central AL is in an area where a favorable low-level and deep-layer shear environment will exist throughout the day. With these favorable kinematic variables in mind, as well as the consideration of a tropical moisture reservoir now nudging northeastward along the 40-50 kt low-level jet, any thunderstorm activity today could exhibit supercellular characteristics. As a result, a few tornadoes and damaging wind gusts are possible across Central AL, generally from 11 AM to 11 PM. By the afternoon, diurnal heating will only add to a more quality boundary layer in some areas, particularly areas south of I-20 per latest HREF mean guidance. SBCAPE could increase to <1,250 J/kg as a result, as well as fostering 3CAPE values in the 80-120 J/kg range. As this area of slightly better boundary layer thermodynamics is possible in association with good kinematics (200-300 0-1 km SRH) & 0-3 km shear vector crossover, a 'Slight Risk' was implemented. A 'Marginal Risk' resides elsewhere. With two separate bands of showers and storms possible, the forecast scenario for severe weather today is somewhat complex. With northwestward extent, forcing increases along with slightly better lapse rates. However, sustained updrafts may struggle here as thermodynamics become weaker and 3CAPE values decrease. This should reduce the severe & tornado threat for the northern portion of the first band and potential second band of convection. Overall, all of Central Alabama is in some degree of risk today as Delta approaches the TN Valley. Severe threats gradually decrease this evening with decreasing buoyancy and the departure of the LLJ. * Rainfall: 2-3" with locally higher amounts is possible across the northwest portions of Central Alabama. 1-2" with locally higher amounts is forecast generally along and south of I-59 and further decrease south of I-85. Any higher totals could lead to minor flooding of low-lying or poor drainage areas. Due to antecedent drier conditions and the somewhat transient west-to-east progression of these features, flooding probability is too low for issuance of a Flash Flood Watch. * Winds: 20-30 mph wind gusts are possible outside of shower and thunderstorm activity. Isolated gusts up to 35 mph are possible across the southwest portions of the area through the early afternoon. Thus, a Wind Advisory is in effect in those areas through 1 PM. Thereafter, the wind field & pressure gradient from Delta should have weakened enough for gusts to drop below advisory criteria. By tonight I show a decreasing trend in PoPs to the northeast as well as rainfall intensity. With the remnant low of Delta lingering near the TN Valley along with the right entrance region of the upper-level jet stream to the north, periods of light rain could persist across the area into tomorrow as well. PoPs remain somewhat elevated as a result, but rain amounts should be on the lighter side with mostly cloudy skies. Drier air and a transition to more westerly flow takes place tomorrow night. Stay tuned for forecast updates. 40/Sizemore .LONG TERM... /Updated at 0427 AM CDT Sat Oct 10 2020/ Sunday night through Friday. As Delta's remnants move away to the east, subsidence and drying is expected Sunday night and Monday morning ahead of an approaching front. A shortwave moving through the Great Lakes and Ohio Valley will drive this moisture-starved front through our region Monday afternoon and Monday night. A few sprinkles may occur over our northern counties, but no measurable rainfall is expected. Under persistent west-northwest flow at 500 mb and high pressure, fair conditions will be prevalent on Tuesday and Wednesday. A bit of southwest flow may develop on Thursday in response to strong vorticity moving through the Northern Plains and Great Lakes. This may be the last in a series of warm days as a sprawling area of high takes shape from the Plains to the Deep South. The associated front will probably have little moisture to work with and appears poised to move through on Thursday night, with much cooler conditions to follow on Friday. 87/Grantham && .AVIATION... 06Z TAF Discussion. Generally MVFR to IFR conditions are in place across Central Alabama terminals with 5-10 kt surface winds out of the E to ENE. Low overcast cloud bases will likely stick around through around sunrise where I begin transition back to MVFR with an increase in easterly winds and higher gusts. This is due to the pressure gradient and remnant wind circulation of Delta to our southwest which will track more toward our area. Through this morning, I expect ceilings to further lift with perhaps a few breaks in the clouds due to mixing. VFR could make a return by the early to late afternoon, though periods of showers and thunderstorms could present flight category issues with gusty winds and reduced visibility. There's never an easy way to make these complicated and messy systems fit in a TAF in a good way. With the overall nature of the forecast, all terminals should expect flight impacts in some fashion throughout the afternoon and perhaps the evening. After heavier rainfall & convection moves east into GA, light rain and lowering cloud bases are forecast overnight and into upcoming TAF period. 40/Sizemore && .FIRE WEATHER... High rain chances and moisture content will continue through Sunday as Tropical Storm Delta moves through the region. Drier air will move in behind the system Sunday night and again Monday night behind a front. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 77 68 76 65 84 / 100 90 80 20 10 Anniston 79 70 77 66 85 / 90 90 70 20 10 Birmingham 78 69 77 67 86 / 90 90 70 10 10 Tuscaloosa 79 69 78 66 88 / 90 80 50 10 0 Calera 78 69 77 66 86 / 100 80 60 10 10 Auburn 79 69 78 67 83 / 90 90 60 10 10 Montgomery 82 72 81 67 88 / 90 60 40 10 0 Troy 82 70 82 67 85 / 90 60 30 10 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... Wind Advisory until 1 PM CDT this afternoon for the following counties: Greene...Hale...Marengo...Pickens...Sumter. && $$