Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
458 FXUS64 KHUN 171741 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1241 PM CDT Tue Jul 17 2018 .UPDATE... For 18Z TAFS. && .NEAR TERM...(Rest of Today) Issued at 939 AM CDT Tue Jul 17 2018 Low stratus clouds and fog are finally beginning to lift/dissipate across the area this morning, with visibilities slowly improving attm. An SPS remains in effect through 10am for the low ceilings/patchy fog (especially in the terrain locations of NE AL/Srn Middle TN). Otherwise, a look at regional radars shows some shower activity bubbling up/dissipating upstream over Srn TN and SEwrd into NW AL. This activity is in response to a sfc cold front sprawled NE to SW across portions of Central/Wrn TN. This boundary will slowly meander Swrd through the day, increasing the coverage of showers and storms this afternoon. As in days past, locally heavy rainfall and gusty winds will be the primary hazards, and the forecast handles this well. The only changes made to the current forecast were to adjust current temps downward a bit thanks to the lower clouds hanging around a little longer than anticipated this morning. Once they break up, temps are expected to rebound nicely to the current temp trend to top out in the upper 80s. .SHORT TERM...(Tonight through Thursday) Issued at 447 AM CDT Tue Jul 17 2018 As this front pushes further south this evening, can not rule out some lingering scattered showers or storms into the early evening hours before ending. As this front stalls to our south, drier and cooler air should push into the area. Lows should drop into the mid 60s to around 70 degrees on Wednesday morning, before warming into the 85 to 90 degree range in most areas (with abundant sunshine). An even cooler night looks to be in store on Wednesday night into Thursday morning. Clear skies and light winds should allow lows to dip into the lower to mid 60s. A bit warmer temperatures are expected on Thursday, as highs climb into the upper 80s to lower 90s, with lows rising back to around 70 degrees. .LONG TERM...(Thursday night through Monday) Issued at 447 AM CDT Tue Jul 17 2018 Upper blocking over the eastern Europe/western Asia region will be a player regarding the extended forecast. This Rex-type block should transition to an Omega style into early next week. Output from the GFS/ECMWF (in comparison to each other) become notably different in the northern stream, regarding positions of systems further east and in the future. Over the North American domain, the main feature noted include a strong and warm upper ridge over the SW CONUS and troughing over the Great Lakes (with the trough amplifying to the SE along the Appalachians next week). A slow transition of the eastern trough to the east will bring unsettled weather across the Tennessee Valley for the weekend. On Friday, chances for convection will continue as the boundary that moved south of the area today, returns northward as a warm front. This will place the area back into the warmer, more unstable sector for Sat/Sun time frame. The ECMWF in comparison to the last nights run, has become aggressive and depicted a sharper trough in the westerlies, similar with the GFS ensemble. This trough amplifying across the Ohio Valley will bring a another cold front across the area during Sunday. Given lift with this front, have raised PoPs to the likely range to end the week. Drier air filtering in behind the front will bring drier weather to start the new work week. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1227 PM CDT Tue Jul 17 2018 Convection in the vicinity of the terminals will increase through the afternoon as a cold front approaches from the N. Vsby reductions and an increase in winds is expected if storms directly affect the terminals, and has been handled with a TEMPO group for a few hours this aftn. Otherwise, convection will end and skies will clear from N to S shortly after sunset. This will set the stage for fog development across the area by midnight, with MVFR vsbys expected by this time. Further reductions are likely by sunrise, with at least IFR (1-2SM) conds by sunrise. As mixing ensues after sunrise, conditions will improve to VFR by 18/13-14Z, lingering through the end of the TAF period Wednesday. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...12 SHORT TERM...KTW LONG TERM...RSB AVIATION...12 For more information please visit our website at weather.gov/huntsville.