Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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253 FXUS64 KHUN 071145 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 645 AM CDT Fri Jun 7 2024 ...New AVIATION... .NEAR TERM... (Today) Issued at 420 AM CDT Fri Jun 7 2024 Current surface observations suggest that winds have begun to veer to NW across the TN Valley as a weak cold front progresses southeastward through the region. Dewpoint temperatures will likely fall into the u50s-l60s for much of the forecast area by 12Z, and with light winds and lingering cloudiness across the eastern half of the region expected to dissipate, patchy fog will continue to develop in our more fog prone locations as temps descend into the l-m 60s. As for the rest of the day, NNW flow aloft of 30-40 knots will persist across the region within the gradient between an upper low shifting eastward across southern Ontario and a subtropical high that will develop southeastward from the southern Rockies into TX. At the surface, NW winds will strengthen later this morning to the east of a ridge (currently centered across the Ozarks), but with only a minor impact from thermal advection, abundant insolation this afternoon will yield highs in the l80s (elevated terrain) and m-u 80s (valley). && .SHORT TERM... (Tonight through Sunday night) Issued at 420 AM CDT Fri Jun 7 2024 The center of the surface ridge (discussed above) will migrate eastward across the TN Valley and into the southern Appalachians tonight. Although the combination of light/variable winds and dewpoints in the m50s would normally be optimal for radiational cooling, high-level clouds will likely begin to spread southeastward into the region from a thunderstorm complex that will originate across eastern NE/KS late this afternoon and spread southeastward through MO before decaying upon reaching the Lower OH Valley by 12Z Saturday. Thus, we have indicated lows in the u50s-l60s for most of the region. Latest guidance from the CAMs and global models suggest that the remnants of the decaying MCS to our northwest will largely bypass our region to the north late Saturday morning, but due to some uncertainty regarding the southward extent of peripheral shower activity, we have included a very low POP for our southern TN zones between 12-18Z. Otherwise, mostly sunny skies and a light southwesterly return flow during the afternoon should boost temps into the u80s-l90s. By late Saturday afternoon, redevelopment of thunderstorms is expected across southern MO in the vicinity of a cold front that will receive a nudge southward as a northern stream vort max diving across the Upper MS Valley induces development of a weak surface low over the Lower Great Lakes. This convective regime will likely expand in coverage Saturday evening, as should spread east-southeastward with time as mid-level winds back to WNW along the edge of the subtropical ridge, which will build progressively eastward into the central Gulf Coast states. However, due to some uncertainty regarding how far south/east storms will spread early Sunday morning, we have only included a low-medium (20-30%) POP for locations north of the TN River. Pending impacts from morning convection, it appears as if redevelopment of at least scattered thunderstorms (30-50% coverage) will occur on Sunday afternoon as a frontal wind shift drifts southward into the forecast area. Should this occur, mid-level westerly flow of 35-45 knots and temps in the 85-90F range (supporting CAPE of 2000-3000 J/kg) could support a few stronger cells capable of producing strong winds and hail. A few showers and thunderstorms will likely continue into the evening hours, before gradually dissipating early Monday morning as a drier airmass is advected into the region. && .LONG TERM... (Monday through Thursday) Issued at 420 AM CDT Fri Jun 7 2024 Forecast uncertainty increases considerably toward the beginning of next week, as the 0Z suite of global models offers a wide array of solutions regarding both the upper flow pattern across the eastern CONUS and eventual position of a cold front that is expected to drift southward through the region early Monday morning. Due primarily to uncertainties regarding frontal location, we have left a low (20-30%) chance POP in the forecast from Monday-Tuesday, especially as the projected orientation and proximity of the boundary (and resultant thermal gradient) may support impacts from additional clusters of thunderstorms that could originate across OK/AR and spread east-southeastward into the central Gulf Coast. By the end of the forecast period, a blocking mid-level ridge is likely to become established across the TN Valley to the north of a 500-mb trough that will drift southeastward into the northern Gulf of Mexico before stalling. This should result in warmer temperatures on Wednesday/Thursday, along with a transition to mainly isolated thunderstorm activity during the afternoon hours. && .AVIATION... (12Z TAFS) Issued at 645 AM CDT Fri Jun 7 2024 VFR/SKC conditions prevail at the HSV/MSL terminals this morning, with patchy but locally dense fog confined to the valleys of northeast AL. Redevelopment of a diurnal Cu field is anticipated around 16Z, with NNW winds expected to increase to 8G16 kts by this time as well. Sfc flow will become lgt/vrbl prior to sunset as a ridge of sfc high pressure build eastward into the region, with sct Ci expected overnight and development of patchy BR/FG possible in a few valley locations once again btwn 4-6Z. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70/DD SHORT TERM...70/DD LONG TERM...70/DD AVIATION...70/DD