Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
000 FXUS64 KHUN 132335 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 635 PM CDT Sat Oct 13 2018 .UPDATE... For 00Z TAFS. && .NEAR TERM...(Tonight) Issued at 314 PM CDT Sat Oct 13 2018 In wake of a cold front that moved through the region last night, a cool northeast flow has reinforced an autumn air mass. Still, the morning status deck has mostly dissipated, allowing temperatures to climb from the mid 60s to around 70 degrees. A mostly clear evening will allow for some decent radiational cooling initially as temperatures fall into back into the 50s. However, clouds will be on the increase by 03-06z as an upper-level disturbance will move out of the South Plains into the mid to lower Mississippi Valley overnight. Ahead of this feature, a shortwave trough and its associated LLJ will lift from the ArkLaMiss and into Northwest Alabama and Middle Tennessee late tonight into Sunday morning. This feature will serve as lifting mechanism for isolated to scattered rain showers overnight, especially areas north of the Tennessee River and the Mississippi border (closer to a weak boundary). This activity should be light, however, as the heaviest activity will remain to the northwest of the region. With winds veering to the southeast/south later tonight, some warm air advection may actually occur late, especially across the southwest zones. Regardless, lows will run in mid 50s to around 60 degrees in most spots. .SHORT TERM...(Sunday through Monday) Issued at 314 PM CDT Sat Oct 13 2018 With a weak front just to the north and west of the region early this week, opportunities for scattered showers (and perhaps a few isolated storms, especially Monday) will be possible. Essentially, the region will be caught in the middle between a building subtropical ridge over Florida and an amplifying upper-trough over the Great Lakes. A series of weak disturbances will rotate along the southeast edge of the trough, helping to initiate this activity. There is a bit of model uncertainty as to how far to the southeast the front will sag. However, the latest model trends suggest that it will remain across Western and Middle Tennessee, allowing for more southerly flow across North Alabama, and thus warmer temperatures (mid 70s to around 80 degrees) and more scattered precipitation chances. As one would expected, the highest chances will exist across far northwest Alabama (closest to the boundary), with more widely scattered to isolated chances further to the south and east over Marshall and DeKalb Counties. .LONG TERM...(Monday night through Friday) Issued at 314 PM CDT Sat Oct 13 2018 A piece of energy over Canada will help shove the longwave trough east into the Northeastern US and thus the cold front into the region late Monday night into Tuesday. Another round of scattered showers and perhaps a few isolated storms will accompany this frontal passage during this period. However, the biggest headline will again be a push of cooler and drier air in its wake as high temperatures will fall into upper 50s to 60s, with lows back into the mid to upper 40s by Tuesday night. The rest of the extended period will be characterized by generally clear conditions and a cool, dry air mass with highs in the 60s to low 70s -- thank to a subtropical ridge building in from the Gulf of Mexico. There is a significant difference in the models by Friday, with the GFS showing a strong upper-trough moving into the Ohio Valley and the ECMWF maintaining the upper- ridge. For now, have not altered much from the previous forecast of slight chance PoPs and 60s temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 635 PM CDT Sat Oct 13 2018 VFR conds prevail for now at both main terminals this early Sat evening. Mid/high clouds though will begin to spread into the area from the west later this evening in advance of a storm system forming over the wrn Gulf states. Some light/occasionally mod shra may also begin to develop/move into the area from the SW later tonight, and a prevailing VCSH has been added to the forecast starting near 06-07Z. With the shra/associated cloud cover, mid level cigs may lower to around 5-7K ft Sun morning, but should remain well above VFR criteria thru the remainder of the TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...AMP.24 SHORT TERM...AMP.24 LONG TERM...AMP.24 AVIATION...09 For more information please visit our website at weather.gov/huntsville.