Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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911 FXUS64 KHUN 050913 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 413 AM CDT Fri Jul 5 2024 ...New NEAR TERM, SHORT TERM, LONG TERM... .NEAR TERM... (Today) Issued at 413 AM CDT Fri Jul 5 2024 A flat subtropical ridge (centered over the Lower MS Valley yesterday evening) will continue to weaken over the course of the early morning hours in response to a northern stream shortwave trough digging southeastward across southern MN. At the surface, an area of low pressure related to the aforementioned trough will shift slowly eastward across southern WI, with a trailing cold front extending southwestward through the Mid-MS Valley and Red River Valley region of OK/TX. We are currently monitoring the progress of a large area of prefrontal convection to our NW (which originated across southern MO/northern AR yesterday evening), but present indications are that this activity will not reach our CWFA prior to 12Z. Nevertheless, a few showers and thunderstorms may develop through sunrise in the strengthening low-level warm advection regime downstream from the MCS, and we have maintained a 20-30% POP to account for this possibility. Low temperatures will be quite warm due to the high moisture content of the boundary layer, and may only reach the u70s-l80s in many locations, with haze and fog possible (especially in the wake of fireworks yesterday evening). Latest high-resolution model guidance suggests that the southwestern edge of the MCS will likely spread southeastward across our forecast area during the late morning hours, with our highest POPs (80-90%) reserved for the 12-18Z timeframe. However, depending on the quality of airmass recovery that can occur in the wake of this system, additional thunderstorms may redevelop this afternoon as the slow-moving cold front begins to enter the region from the northwest. With mid-level southwesterly flow predicted to strengthen into the 20-25 knot range as the northern stream trough shifts into the western Great Lakes and the subtropical ridge becomes more centered along the Atlantic coast of GA/northern FL, a few strong storms will be possible given CAPE in the 2000-2500 J/kg range. Finally, although the max temperature forecast is a bit uncertain due to the anticipated coverage of clouds and precipitation early in the day, it seems reasonable to believe that most locations will at least briefly touch the lower 90s, which (coupled with dewpoints in the mid 70s) will achieve Heat Advisory criteria once again, and we will maintain the NPW at the present time. && .SHORT TERM... (Tonight through Sunday night) Issued at 413 AM CDT Fri Jul 5 2024 Showers and thunderstorms will likely begin to diminish in coverage and intensity around sunset this evening, but with the cold front still to our northwest at 0Z, we will maintain a low- medium POP for most of the region through late this evening (highest in the southeast). Latest model consensus indicates that the cold front will indeed clear our region early Saturday morning, with only a low (15-20%) POP maintained for our southeastern counties during the day to account for some uncertainty regarding the precise location of the boundary. Although dewpoints may fall into the l-m 60s in the postfrontal airmass, highs should still manage to reach the lower 90s Saturday, with lows falling into the u60s-l70s Sunday morning. Present indications are that the front will begin to retreat northward at some point Sunday afternoon/evening, ushering a warmer and more humid airmass into the region once again, and we have increased POPs both periods to account for this. && .LONG TERM... (Monday through Thursday) Issued at 413 AM CDT Fri Jul 5 2024 By Monday, we will be back in a warm sectored airmass with upper ridging centered off the Atlantic Coast and an upper trough making its way through the central Plains and into the Midwest. The upper ridge over the Atlantic looks to remain dominant over a large portion of the Southeast through at least the mid-week period, as the upper trough becomes less amplified as it moves across the Great Lakes and into Canada. This will keep near seasonable temperatures (highs in the upper 80s/lower 90s) in place with daily chances for rain and storms, peaking (40-60%) during the afternoon diurnal heating hours. The track of the eventual remnants of Hurricane Beryl is still pretty uncertain at this time, and low confidence exists regarding whether or not the Tennessee Valley will see any rain from this system or not. For that reason, have stuck with blended guidance for PoPs given that it is at the 6-7 day range which suggest a 30-50% PoP Wednesday and Thursday. Overnight lows will be in the upper 60s to mid 70s each night. && .AVIATION... (06Z TAFS) Issued at 116 AM CDT Fri Jul 5 2024 VFR conditions will prevail through the early overnight hours before showers and thunderstorms arrive over the area around sunrise. Expect showers and thunderstorms to persist on and off through much of the TAF period, with reductions to MVFR conditions likely although confidence in timing remains low. Brief reductions to IFR conditions will be possible during heavier showers and thunderstorms, and gusty winds may also accompany the heavier shower/storm activity. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Heat Advisory until 7 PM CDT this evening for ALZ001>010-016. TN...Heat Advisory until 7 PM CDT this evening for TNZ076-096-097. && $$ NEAR TERM...70/DD SHORT TERM...70/DD LONG TERM...26 AVIATION...25