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Area Forecast Discussion
505 FXUS64 KHUN 301537 AAB AFDHUN Area Forecast Discussion...UPDATED National Weather Service Huntsville AL 1037 AM CDT TUE AUG 30 2016 .UPDATE... Morning update. && .DISCUSSION... Radar and visible satellite are clear across the forecast area this morning. Lack of cloud cover has allowed temps to warm up into the lower 80s so far, heading towards the lower 90s by this afternoon. Added in isolated showers/thunderstorms for this afternoon in NE AL and southern middle TN, mainly for the higher terrain. Weak convergent winds and a weak disturbance moving in from the NE combined with daytime heating may be just enough. Some short-term guidance is hinting at some isolated convection too. However, will have to see if dry air will win. Otherwise, the rest of the forecast is on track for today. JMS && .AVIATION... (Issued 607 AM CDT TUE AUG 30 2016) For 12Z TAFs: VFR conditions will continue today at HSV, but patchy fog will result in tempo MVFR fog conditions at MSL until around 13z this morning. VFR conditions will be the rule at both HSV and MSL after 13z. Some more patchy fog is expected at the terminals at the end of the TAF period. Added in a tempo 5sm br at both HSV and MSL after 10z Wednesday. TT && .PREV DISCUSSION... (Issued 233 AM CDT TUE AUG 30 2016) As of 0730Z not much has changed when comparing current Water Vapor imagery to the same time yesterday. The high to our north, the low off the GA/SC coast and the low off the TX coast have shifted ever so slightly westward. Regional 00Z soundings and satellite derived PWATs indicate drier air in place across the southern Appalachians with PWAT values around 1.2 inches. This region is in an area of subsidence between the high to our north and the low along the GA/SC coast. Latest guidance has both the high and the low shifting further W/SW with time today. As a result the drier air mainly in the mid- levels will be advected into the TN Valley. Not quite buying into the upper 50s dewpoints across the eastern half of the area this afternoon shown by a few of the short- term guidance. But do think dewpoints will lower an additional 1-3 degrees compared to yesterdays values. This should all translate into a dry forecast for today with any shower/thunderstorm activity remain outside of the TN Valley. A weak shortwave evident in WV across NE TN may provide just enough lift to spark an isolated storm over the higher terrain in TN/GA but think our area will remain storm free. Temperatures this afternoon will again climb into the low to mid 90s but due to the drier air it should feel less humid today. Tonight in Wednesday a low pressure system is forecast to drop SE out of northern Canada towards the NE US sending a pre-frontal trough towards the the TN Valley. While this is occurring the dry air in place today gets shifted back to the east and we will see a slight increase in low/mid-level moisture. Latest guidance differs to some degree on the timing of the pre-frontal trough on Wednesday. But believe that with the slight uptick in moisture, strong diurnal heating, and lift with the trough, we should see isolated showers and thunderstorms develop Wednesday afternoon. The best chances for storms will likely come on Thursday as the main front rolls through the area. Nudged up PoPs and kept the chance wording for the eastern half of the area as they will be closer to the upper level trough axis and better lift. At this point not expecting other than a few isolated strong storms as shear (20kts) and CAPE (1200 J/kg) aren`t supportive of anything beyond that. The remainder of the forecast Friday through the Labor Day weekend is shaping up nicely. We remain in northerly flow through the period, which will help to keep dewpoints near the 60 degree mark. Highs are forecast to range from the mid to upper 80s with overnight lows in the low to mid 60s! Should be a nice weekend for outdoor activities. Stumpf && .HUN Watches/Warnings/Advisories... AL...NONE. TN...NONE. && $$ For more information please visit our website at weather.gov/huntsville.