Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
000 FXUS64 KHUN 221954 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 254 PM CDT Mon Apr 22 2019 .NEAR TERM...(Tonight) Issued at 254 PM CDT Mon Apr 22 2019 Upper level ridging continues to amplify this afternoon as we warm into the upper 70s to low 80s. Satellite imagery shows mostly clear skies, thanks to surface high pressure over the Northern Gulf blocking us off from moisture and keeping dew points in the 40s. Calm winds and mostly clear skies continue tonight, but increasing ridging aloft will also increase warm air advection. As the surface high begins to slide eastward, weak south to southwesterly flow will resume and dew points will increase to the low 50s. Some convective blowoff cirrus from strong storms over the Southern Plains will increase coverage of high clouds tonight, further limiting the potential for radiational cooling. Therefore, lows tonight will only get down to the mid 50s. .SHORT TERM...(Tuesday through Wednesday) Issued at 254 PM CDT Mon Apr 22 2019 Above average temperatures persist through midweek with highs each day in the upper 70s to low 80s and lows in the upper 50s. A cutoff low at 500mb will remain over the Southern Plains through Wednesday, as it will be blocked by the ridging aloft over the Southeast. Southwesterly flow at the surface will allow moisture to gradually return, as seen by dew points reaching the upper 50s, causing cloud cover to steadily increase Wednesday. Winds remain fairly light both Tuesday and Wednesday. .LONG TERM...(Wednesday night through Sunday) Issued at 254 PM CDT Mon Apr 22 2019 Late Wednesday into Thursday, the cutoff low over the Southern Plains will phase with a shortwave crossing the Great Lakes region late next week. This trough will then progress through the Tennessee Valley on Thursday. A surface low will develop over the Western Gulf and deepen ahead of the trough, as the trough begins to lift and weaken into an open wave. Ahead of the surface low, a boundary will stall over the Ohio Valley late Wednesday into early Thursday. Moderate southwesterly flow at 850 mb will raise PWATs above 1" as moisture pools south of the stalled boundary. Combined with weak isentropic lift and vorticity advection, rain chances increase on Thursday ahead of an approaching cold front. Fitting with the summer- like pattern this week, instability will increase Thursday, implying at least a slight chance for thunderstorms to develop Thursday afternoon. These are expected to increase in coverage through Thursday night as the low and cold front approach the TN Valley. While there are still discrepancies with timing of the front and where the low will track, forecast precipitation remains between 0.5" and 1" total with this event. Some lingering showers, perhaps an isolated thunderstorm, are possible Friday morning and early afternoon as the weak cold front passes through the area. Overall air mass changes will not be significant behind the front, as lows Friday night will be in the mid 50s, approximately five degrees cooler than Thursday night. Saturday should be a warm, pleasant day with highs again reaching the low 80s, mostly clear skies, and low chances for rain. Another shortwave will enter the NW Pac on Sunday morning and rapidly traverse into the Midwest by Sunday afternoon. The marginal PVA and lee surface cyclone tracking toward the Great Lakes may be enough to bring a second chance of rain Sunday morning, with an isolated threat for thunderstorms. Confidence in this is low and will need to be monitored over the next several days. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1212 PM CDT Mon Apr 22 2019 VFR conditions will prevail through the TAF period across the region. Light winds will become calm this evening as they back to southeasterly, then increase between 5 and 10 knots tomorrow from the southwest. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...30 SHORT TERM...30 LONG TERM...30 AVIATION...30 For more information please visit our website at weather.gov/huntsville.