Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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963 FXUS64 KHUN 230258 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 958 PM CDT Wed May 22 2024 ...New NEAR TERM... .NEAR TERM... (Rest of tonight) Issued at 958 PM CDT Wed May 22 2024 A belt of moderately strong (30-40 knot) WSW flow aloft will persist across the TN Valley region overnight, maintaining an overcast coverage of high-level convective debris clouds across the region (originating from multiple clusters of thunderstorms currently in progress from southeastern AR into central TX). Recent high- resolution model guidance suggests that light rain along the northeastern flank of the loosely organized MCS to our WSW will spread east-southeastward through northern AL between 3-9Z, perhaps bringing some measurable precipitation to mainly the southwestern corner of the forecast area. We have left a low- medium (20-40% POP) in the grids during this timeframe to address this scenario, with chances for rain lower across the northeastern corner of the CWFA as coverage should diminish with eastward extent. Although elevated CAPE in the 500-1000 J/kg range would normally support a risk for thunderstorms, lightning activity has recently been on a downward trend from the Arklamiss region northeastward, and we will only include a very low probability for embedded thunderstorms overnight. Present indications are that the greatest concentration of nocturnal convection should be displaced to our northwest, where a convectively-induced vort max will shift northeastward and interact with a subtle low-level convergence boundary. Due to the presence of thick clouds and abundant low-level moisture (dewpoints in the mid 60s), lows will be very mild and in the 65-70F range. && .SHORT TERM... (Thursday through Saturday) Issued at 255 PM CDT Wed May 22 2024 Thursday morning we will be greeted again by the lingering front promoting more widespread showers and perhaps a few rumbles of thunder across the area. Rain and thunder chances will decrease through mid day as the front moves on. Chances for storms will then transition to being driven by day time heating. If we can clear out and heat up, strong to severe storms will be again possible Thursday afternoon. Beyond Thursday afternoon, several shortwaves will ripple NE through the area and promote high chances for rain overnight on Thursday and through the day on Friday. This will be mostly rinse and repeat into Saturday as rain and storm chances again pick back up in the afternoon. Each day storms will pose a threat for hail, gusty winds, and frequent lightning. Those with outdoor activities this weekend will need to remain vigilant. Aside from storm chances, our temps will remain in the mid to high 80s making for very muggy conditions during the dry slots of the day. && .LONG TERM... (Saturday night through Tuesday) Issued at 255 PM CDT Wed May 22 2024 No big changes made to the extended portion. A powerful system moving from the south/central Plains to the southern Great Lakes will keep chances of showers and thunderstorms in the forecast for the Tennessee Valley this weekend into Tuesday. More numerous, and possibly strong to severe storms look more probable Sunday into Memorial Day. These will be preceding, and possibly accompanying a cold front moving across the area Monday. Dry weather and slightly cooler conditions return late Tuesday into Wednesday. Previous discussion... Issued at 354 AM CDT Wed May 22 2024 A more vigorous shortwave will pivot from the central/southern Plains into the Ohio Valley/Great Lakes on Sunday, bringing widespread convection to portions of the Mid South and lower Ohio Valley -- including the potential for a regional outbreak of severe weather over those regions. Closer to home here in the Tennessee Valley, a threat for strong to severe thunderstorms will also exist. Guidance hints at an initial wave of prefrontal convection during the morning hours on Sunday, followed by an additional round during the evening hours (into portions of the overnight hours) directly along the cold front has it pushes through the area. This second round would be more likely to pose a threat for severe weather given the potential storm environment in place. However, it is too early to get too specific on timing given uncertainties in the evolution of this system and what exactly the storm environment would support. Still this bears close watching in the coming days, especially given that it will occur during the busy Memorial Holiday weekend. Additional chances for showers and storms will exist Monday (40-60%) and Tuesday (20-30%) before ridging helps to dry us out by the middle of next week. By Tuesday, guidance favors a subtle air mass chance as drier air works its way in and highs in the upper 70s to lower 80s will be common. && .AVIATION... (00Z TAFS) Issued at 709 PM CDT Wed May 22 2024 Convection which initiated earlier today in the vicinity of a subtle low-level convergence axis (positioned to the immediate N/W of the local area) will continue to spread northeastward and away from the terminals early this evening. However, bkn-ovc layers of As/Cs debris clouds will remain in place across the region for much of the evening/early morning period. Models suggest that thunderstorm coverage may begin to increase once again, perhaps as early as 8-10Z, as a convectively-induced vort max (originating from storms currently in progress from southern AR into north- central TX) begins to spread east-northeastward and interact with the stalled sfc boundary to our NW. Although timing may need to be adjusted, we have included PROB30 groups at both airports btwn 10-15Z to account for this scenario. In the wake of any early morning storms, overcast mid-level clouds will likely keep the local airmass somewhat stabilized for the remainder of the period, with only partial clearing expected after 20Z. Sfc winds will remain from the SSE at night and SSW during the day, with prevailing speeds of 5-10 kts. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70/DD SHORT TERM...RAD LONG TERM...AMP AVIATION...70/DD