101 FXUS64 KBMX 062347 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 647 PM CDT Tue Oct 6 2020 .UPDATE... For 00Z Aviation. && .SHORT TERM... /Updated at 1035 AM CDT Tue Oct 06 2020/ Just a few minor updates to the afternoon forecast with some rain showers continuing in the extreme southeast along a moisture boundary. Otherwise, Central Alabama remains high, dry and warm. Summer-like conditions are expected to return by tomorrow as we approach the upper 80s to near 90. 17/KLAWS Previous short-term discussion: /Updated at 401 AM CDT Tue Oct 06 2020/ Today and Tonight. Currently, a broad footprint of high pressure extends from the Northeast to along the East Coast and southwestward into the TN Valley/Deep South. A subtropical ridge is positioned to our southeast with a synoptic trough moving east across the Upper Midwest/Great Lakes Region. The result is an area of southwesterly flow aloft across Central AL which overlaps our rather dry, continental airmass. PWs are quite low, on the order of 0.6-0.8" for most places across Central AL this morning per mesoanalysis and our most recent RAOB. The exception is the far southeast where PWs exhibit an increase to ~1.2" near TOI/EUF (PWs further increase to 1.9-2.1" across portions of FL). This increase is along an axis of moisture extending from the remnants of 'Gamma' across the Gulf of Mexico. With evidence of at least weak isentropic ascent near here, our southeast counties may see an isolated shower this afternoon, though I only kept PoPs at a generous 15%. We'll be hard-pressed to see any measurable rainfall with the generally stable/dry airmass. Otherwise, look for a warm day with highs in the upper 70s to mid 80s. I kept warmest temps in areas north of I-85 as much less cloud cover & dry air will combine for a strong diurnal temperature increase. These temperatures should quickly fall this evening with lows forecast in the 50s & 60s, just above respective dewpoints. Wednesday morning and afternoon. Once the trough to our north exits off the East Coast Wednesday morning, guidance suggests a period of broad, low-amplitude height rises across the Southern CONUS which becomes more prominent farther west. With Hurricane 'Delta' across the southern Gulf, a rather warm/dry day is forecast in response to ample sunshine and subsidence across the Deep South. I bumped up high temps a degree or two over previously advertised as a result, generally in the low to upper 80s. Trends in deterministic & MOS guidance both support this increase and I'm not too surprised given the overall setup and antecedent dry low-level conditions and progged 1000-850 mb thickness values. 40/Sizemore .LONG TERM... /Updated at 1235 PM CDT Tue Oct 06 2020/ Overview. Hurricane Delta will be the primary feature of concern over the long-term forecast period. Ridging aloft, centered to the east of the area over the Bahamas along with an additional area of low- latitude ridging will prevail over the Southern Baja California Region. A weakness in the H500 pattern continues to be depicted by global modeling which will support the northward advancement of Delta from the West-Central Gulf of Mexico into Louisiana late Friday into Saturday. There is loose overall model consensus with a shortwave trough digging over the Central Plains that will help to pull the system northeast with time. The system looks to become absorbed into the shortwave trough during the day on Sunday. The system is expected to initially travel northward after landfall, roughly along the Mississippi River, followed by a gradual turn more to the northeast, with the track taking the system across Northern Mississippi and into Central Tennessee during the day on Sunday. The progressive rather zonal flow pattern depicted will help move the system quickly further northeast as we head into Monday next week with shortwave ridging quickly becoming established over the area. Breezy Conditions Expected impacts will be breezy conditions with winds generally from 15-25 mph across the western portion of the forecast area from south to north starting Saturday afternoon and continuing into early Sunday morning. Rainfall Heaviest rainfall is expected with general amounts in the 2-4 inch range with the highest potential closer to the Alabama/Mississippi state line. The relatively quick storm motion will help keep rainfall amounts lower though even values of this magnitude still may contribute to localized flooding concerns in low-lying, poor drainage areas and along area rivers and streams. Tornado Risk Portions of our western counties are expected to be within the right front quadrant of the tropical system, which experiences the worst conditions and where tornado potential is typically highest. Wind profiles will be favorable for a few fairly weak and short- lived tornadoes. The conditional environment will be dependent on surface-based instability which at this time appears to be supportive of a few stronger updrafts that could support a tornado risk across portions of the western portion of the forecast area mainly on Saturday. Overall Forecast Outlook The rest of the forecast generally will involve decreasing high temperatures as cloud cover and precipitation chances increase from Thursday through Sunday. A warming trend will develop as shortwave ridging moves into the area on Sunday and Monday Overnight lows will increase as we develop a more southeasterly low-level flow with lows in the 60s becoming common by Friday followed by a few places across the southern third of the forecast area experiencing lows in the 70s. While we will initially experience subsidence being on the periphery of the system, cloud cover and rain chances will both increase from the south on Thursday through Saturday. Expect a gradual decrease in activity from the southwest as we move into early Sunday with the best chances across the north and the east. Winds will initially be out of the northeast 4-8 mph to start the period followed by more easterly flow on Friday with speeds 5-10 mph. Winds will gradually increase out of the southeast during the day on Saturday 6-12 mph. A more southerly component to the winds is forecast across the southwest later in the day southwest with winds increasing 10-20 mph. A more southerly flow will overspread much of the area by Saturday night with winds 15-25 mph with highest speeds west and southwest. Highest winds 15-25 mph will be experienced by the west and northwest counties as we move through early in the day on Sunday. A southwest flow is expected to develop as the system moves to the north of the area later in the day on Sunday with speeds 10-15 mph. Winds will gradually decrease to 4-8 mph Sunday night with south winds 5-10 mph on Monday. 05 and 56 && .AVIATION... 00Z TAF Discussion. All but south TAFs (MGM/TOI) in C AL should remain VFR through the 24 hour forecast period. Mainly high clouds are expected across the northern half of the state if any. Winds should remain light for all. With moisture expected to continue to flow across the southern half of the state from the Gulf of Mexico and Delta, some MVFR cigs are possible tonight into the early morning hours for MGM/TOI. However, no precipitation is anticipated. 08 && .FIRE WEATHER... Dry weather and light east-northeast winds will persist through Wednesday. Minimum RHs will be in the 35-50 percent range. Rain chances will increase for Thursday through the weekend as a result of Hurricane Delta. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 53 85 56 84 63 / 0 0 0 10 20 Anniston 56 86 58 86 65 / 0 0 0 10 20 Birmingham 58 87 60 85 66 / 0 0 0 10 20 Tuscaloosa 57 88 61 86 67 / 0 0 0 20 30 Calera 58 86 61 84 66 / 0 0 0 20 20 Auburn 62 85 63 83 67 / 10 0 0 20 20 Montgomery 63 88 66 85 70 / 10 0 0 30 30 Troy 64 87 67 84 70 / 10 0 0 40 30 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$