Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
810 FXUS64 KHUN 201056 AAA AFDHUN Area Forecast Discussion...UPDATED National Weather Service Huntsville AL 456 AM CST Tue Feb 20 2018 .UPDATE... For 12Z TAFS. && .NEAR TERM...(Today) Issued at 347 AM CST Tue Feb 20 2018 Mild temperatures were observed at 07Z in the middle to upper 60s for most locations. This was due to southerly flow holding at at 5-10kt. The exception is along the GA border where the western edge of weak cold air wedging was occurring. Low clouds have edged into far northeast AL, but do not expect the dense fog now over north central and northeast GA to reach this area (with the exception of mountaintop fog due to the clouds). As as been advertised, a mid and upper level ridge has built off the southeast U.S. coast, enabling a large southerly fetch of warm and moist air to flow into the TN valley. Record highs will be neared or set again today as a result, with forecast soundings supporting 80-81F in the HSV/MSL areas, and upper 70s elsewhere. The low clouds this morning will likely keep the 4A9/Lookout Mountain area in the middle 70s. .SHORT TERM...(Tonight through Thursday) Issued at 347 AM CST Tue Feb 20 2018 The short range models continue to indicate a weak upper impulse rotating northward from the Gulf of Mexico around the western portion of the anti-cyclone. This will generate isolated light showers or sprinkles tonight into early Wednesday, mainly for areas of eastern AL into GA. Meanwhile, the NAM/SREF and ECMWF remain constant in the upper ridge holding the frontal band precipitation to our northwest and west through Wednesday and possibly into Thursday as well. Forecast soundings indicate a strong capping inversion in the warm sector further southeast. In this scenario, the northwest corner of AL into western portions of southern middle TN will stand the best chance of showers reaching their areas late Wednesday into Thursday as the cold front edges close to these areas, but unlikely through the area. The GFS continues to be the outlier, and aggressively driving a cold pool and the precipitation band more fully into the TN valley. Will be siding with the NAM/ECMWF/SREF in this regard to PoP, with low chances southeast and likely just touching the northwest tip of AL. Temperatures on Wednesday should still reach the upper 70s to lower 80s in the warm sector. Thursday is a bit more questionable with the rain/cloud area north and west, so went with low to middle 70s north, and upper 70s south of the TN River. .LONG TERM...(Thursday night through Monday) Issued at 347 AM CST Tue Feb 20 2018 The lingering frontal boundary and warmer than normal temperatures highlight the extended forecast. The upper ridge is still anchored in the Western Atlantic, stalling the front to our NW. There is still some model disagreement on if the front will start to enter the TN Valley Thurs before lifting back northward Thurs Night/Fri or if it will remain stalled out to our NW. The GFS is still the one who lets the front dip into the TN Valley and has the earliest timing with front compared to the ECMWF, Canadian and NAM who will not let the front budge until this weekend. Kept in the chance for a few showers Thurs night with weak lift, the amount of moisture in place and WAA. Overnight lows will be mild around 60 degrees. The stubborn ridge starts to break down on Friday as a upper level trough digs into the Four Corners region. As southerly flow picks up with the increased pressure gradient, the additional WAA will help afternoon temps into the upper 70s. Precip chances still linger into Friday, however just looking at isolated showers. As the trough ejects from the Four Corners this weekend it will develop a sfc low near TX/OK that will lift into the MS Valley on Saturday. Temperatures will be warmer than normal and plentiful moisture already in place across the region ahead of the front. Highs on Saturday will be in the lower 70s. The front will push into the TN Valley Sat Night/Sunday with showers and thunderstorms possible along and ahead of the front. Models are in better agreement with the weekend set up, but it is still too early to list any potential hazards. The front will move out of the area Sunday night/early Monday, with cooler and drier air filtering in behind it. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 456 AM CST Tue Feb 20 2018 VFR flight weather conditions are expected today. Multi-layer clouds will develop by late morning into early afternoon. The clouds will be scattered at 030-035agl with ceilings around 050agl. Isolated light showers or sprinkles will be possible from these clouds as they lower to around 020agl (MVFR) tonight, but have left out of the terminals at this time. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...17 SHORT TERM...17 LONG TERM...JMS AVIATION...17 For more information please visit our website at weather.gov/huntsville.