318 FXUS64 KBMX 062018 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 318 PM CDT Tue Aug 6 2019 .SHORT TERM... /Updated at 0304 PM CDT Tue Aug 06 2019/ This Afternoon and Tonight. Temperatures are quite warm this afternoon with readings in the lower to middle 90s. However, with surface dewpoints below 70 degrees, heat indices are mainly in the 95-100 degree range. Showers and thunderstorms will remain isolated into the early evening hours. A MCS will likely move across eastern Tennessee late tonight and brush northeast Alabama early Wednesday morning, probably after sunrise. 58/rose .LONG TERM... /Updated at 0307 AM CDT Tue Aug 06 2019/ Wednesday through Monday. The mid-level anticyclone which has been parked over the Four Corners region for many days will move eastward into Texas through the week due to a Pacific trough moving onshore along the West Coast. The associated subtropical ridge will build eastward over the northern Gulf. Meanwhile a deep upper low for early August in the Hudson Bay vicinity will result in an amplifying trough over eastern Canada and the northeastern CONUS. The tightening height gradient between these two features will place Central Alabama along the southern fringes of enhanced northwest cyclonic flow aloft, with various convectively enhanced shortwaves moving through. As the trough lifts out this weekend, the ridge will continue to move eastward and become centered over the ArkLaTex. On Wednesday, a shortwave trough will move quickly eastward from eastern KY/TN to the Central Appalachians. Meanwhile, the associated weak cold front will begin to stall out near the TN/AL border with a pre-frontal trough located over our northern counties. Despite the presence of the front and pre-frontal trough, convective development is uncertain as synoptic-scale subsidence will move in behind the departing shortwave, and mean mid-level RH values will be limited. Therefore convective development will be dependent on any boundaries/MCVs leftover from any upstream convection that develops tonight. Will also need to monitor an MCS that develops in the Central Plains and will be moving through the Ozarks Wednesday morning, but currently only the 12km NAM indicates it reaching our area. Will keep low-end scattered PoPs in the forecast, slightly higher across the northern counties near the pre-frontal trough and the far southeastern counties closer to slightly better moisture and the sea breeze. With SBCAPE values potentially near 4000 J/kg, high DCAPE, and effective bulk shear potentially as high as 25-30 kts, the environment will be conditionally favorable for strong to isolated severe storms across the northern half of the area. However, this would be very conditional upon updrafts overcoming the subsidence/dry air entrainment to become sustained. Mid-level lapse rates are also forecast to weaken during the day as the ridge tries to build in. Heat indices may reach 105 degrees in West Alabama Wednesday afternoon, and will add a mention of this to the HWO. Additional MCS development will probably occur over KS/western MO Wednesday night, but guidance is not very bullish on this activity reaching our area on Thursday with gradually rising heights. PWATs do begin to increase from the west and some widely scattered showers/storms will be possible. Heat indices may reach 105 degrees in some of the southern and far western counties Thursday afternoon, and will add a mention of this to the HWO. An axis of 2-2.25 inch PWATs will set up from the Central Plains southeastward to Georgia Friday through the weekend, ahead of another cold front. This front should stall out just north of our area due to the ridge, though the eastern portions of the front may approach our far eastern counties from Georgia as a back door front. The increased moisture should result in an increased coverage of showers/storms during this period, with the possibility of one or more MCSs as convectively enhanced waves rotate around the ridge. Warm mid-level temperatures (-5 to -4C at 500mb), will limit potential storm strength, but some locally heavy rainfall may be possible. Will have to continue to monitor heat indices, but the increased precipitation/potential cold pools will hopefully keep them below advisory criteria. Heat indices may reach advisory criteria during the first half of next week depending on how strongly the ridge builds in. 32/Davis && .AVIATION... 18Z TAF Discussion. VFR conds will be the prevailing flight category thru the period. Lcl IFR conds possibly at KTOI thru 00z due to diurnal storms. A weak low level trof was located between KMGM and KTOI. Sfc winds were mainly from the west-northwest north of this boundary, with west-southwest flow south of the boundary. Better coverage of convection will be south of the boundary, and included VCTS at KTOI thru 01z. Low cigs and fog possibly overnight at KTOI between 09z and 13z. 58/rose && .FIRE WEATHER... A few showers and thunderstorms through the early evening hours, otherwise mostly clear. Low clouds and fog are possible south of I-85 from 3 am through 8 am Wednesday. A decaying convective complex will pass across northeast early Wednesday morning. This system will push an outflow boundary into north Alabama on Wednesday and trigger scattered thunderstorms, mainly north of I-20. No critical fire weather conditions are anticipated. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 70 92 69 93 71 / 10 40 20 30 30 Anniston 71 92 70 93 72 / 10 40 30 30 20 Birmingham 73 93 73 95 75 / 10 30 30 30 20 Tuscaloosa 73 95 74 95 75 / 10 20 30 30 20 Calera 71 94 71 94 72 / 10 20 30 30 20 Auburn 71 91 72 93 72 / 20 20 30 30 10 Montgomery 73 95 74 96 74 / 20 20 20 30 10 Troy 71 93 72 94 72 / 20 30 20 30 10 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$