Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
951 FXUS64 KHUN 250529 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1229 AM CDT Sun Jun 25 2017 .UPDATE... For 06Z TAFS. && .NEAR TERM...(Tonight) Issued at 808 PM CDT Sat Jun 24 2017 Significantly quieter weather across the Tennessee Valley this evening as opposed to the last couple of evenings as "drier" air continues to the filter into the region. The latest surface analysis shows a frontal boundary stretching from the NC/SC coastal plain across central Georgia and into southern AL/MS. In its wake, high pressure continues to slowly build across north Alabama with light northerly flow and dewpoints in the lower to middle 60s. Infrared imagery and the last few visible images for today show scattered to broken mid/high clouds streaming across the area so not expecting completely clear skies overnight. Given some continued surface gradient and cloud cover along with drier air filtering in not anticipating too many fog issues. Will issue quick update to account for temp/sky trends but no major changes are planned. One quick hydro note, the Paint Rock at Woodville crested early today below action stage and is now falling steadily. However, we are monitoring the Flint River at Brownsboro which has risen to 16.6 feet or about 1/2 a foot below flood stage. .SHORT TERM...(Sunday through Tuesday) Issued at 240 PM CDT Sat Jun 24 2017 The forecast area will remain beneath a broad cyclonic flow regime on Sunday/Sunday night, although mid-level winds are expected to veer more to the west-northwest as the subtropical ridge weakens and retreats to the east while the Great Lakes vort max dampens and ejects northeastward into New England. At the surface, a reinforcing dome of high pressure will build southeastward across the Great Plains on Sunday...providing a steeper pressure gradient and a maintaining north-northeast flow around 10 knots. Although CAA will not be particularly strong, forecast soundings from the NAM/GFS/ECMWF all indicate that an early morning inversion will be slow to mix out through the day...and this should translate to high temps a few degrees cooler than those observed today. Scattered mid and high- level clouds will prevail through the day, but may diminish sufficiently tomorrow night to allow for stronger radiational cooling. Lows on Monday morning have been adjusted to reflect this, with most locations falling into the m50s-around 60. Conditions will also be favorable for early morning fog development...especially in valleys and near large bodies of water...and this has been included in the forecast. A slightly stronger mid-level wave forecast to dig into southern Ontario by 12Z Monday should lead to gradual amplification of the broader longwave trough Monday night/Tuesday. The base of this trough will likely spread southeastward across the region on Tuesday...but with synoptic scale ascent expected to be maximized late Monday night a low chance POP for light showers has been included for the northern half of the region between 27/06-12Z. Based on the dry nature of the boundary layer, the coverage of any shower activity should be quite low. Regardless, an increase in cloud cover during the same period should result in slightly warmer low temperatures on Monday night/Tuesday morning. Any lingering precipitation/cloud cover will rapidly clear the region by 18Z Tuesday...with afternoon temps warming into the l80s once again. .LONG TERM...(Tuesday night through Friday) Issued at 240 PM CDT Sat Jun 24 2017 The TN Valley will be on the western periphery of a departing longwave trough, with northwest flow over much of the region at the start of the long term period. This trough will shift off the Atlantic coast early Wednesday morning as a broad upper ridge builds into the central CONUS. After a rather cool start on Wednesday morning, with temps dropping into the upper 50s, a moderating trend will begin and persist through the end of next week. The subtropical ridge tries to build northward into the region, with winds shifting to the south. This will filter in warm and moist Gulf air to the TN Valley, bringing us our more typical conditions expected for late June. Temperatures will generally warm into the mid to upper 80s each afternoon, and overnight lows will drop into the 60s. Rain returns to the forecast area beginning on Thursday, as moisture continues to advect into the region. This will bring a return of diurnally driven thunderstorms Thursday and Friday afternoon, which will diminish after sunset each night. The better rain chances look to be on Friday, as a trough digs through the Central Plains and into the MS and TN Valleys, helping aid in the diurnally driven convection. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1130 PM CDT Sat Jun 24 2017 High pressure continues to build slowly into the region on the heels of a cold front sinking toward the Gulf Coast. The result will be VFR conditions across the Tennessee Valley over the next 24 to 48 hours with primarily middle and high clouds through the day on Sunday. Northerly winds may be briefly gusty at times on Sunday during peak mixing. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...15 SHORT TERM...70/DD LONG TERM...73 AVIATION...15 For more information please visit our website at weather.gov/huntsville.