Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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651 FXUS64 KHUN 242338 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 638 PM CDT Tue Sep 24 2024 ...New AVIATION... .NEAR TERM... (Rest of Today and Tonight) Issued at 233 PM CDT Tue Sep 24 2024 The remainder of the day will see increasing rain and storm chances as a cold front creeps in from the west. SPC mesoanalysis indicates 2500-3000 J/KG of CAPE present in NW AL, with totals decreasing to the east. This, coupled with 40-45 KTS of bulk shear will certainly be sufficient enough to support more organized storms and maintain our severe threat this afternoon. Current idea is that scattered showers and storms will develop across the area from 1-3 PM and begin to combine into multicell clusters. Main threats will be damaging winds and frequent lightning. The severe threat looks to greatly diminish after sunset with the loss of daytime heating. The cold front looks to slowly continue to push east and will likely bisect a portion of our area for much of the night. The lingering boundary will support continued rain through the night along and east of the front, which will likely be roughly east of I-65. Enough CAPE may linger to support some thunder overnight but the concern will quickly transition to heavy rainfall and localized flooding. The flooding concern is driven by the high possibility for training storms overnight. While cold front driven rain will come to an end tomorrow, a bulk of the rainfall will likely fall tonight with 1-3 inches possible with highest totals in the east. If on the roads tonight or early tomorrow morning make sure to watch out for localized flooding and ponding of water. && .SHORT TERM... (Wednesday through Friday) Issued at 233 PM CDT Tue Sep 24 2024 Rain is likely to start the day on Wednesday with continual support from the frontal boundary. The front looks to stall over our area as it begins to interact with Tropical Storm Helene. A medium chance of showers and thunderstorms, scattered in nature, are likely through most of the day tomorrow, however the severe threat will be significantly less than today. Rain chances will decrease through the evening however with Tropical Storm Helene continuing to move NE, a brief period of low rain chances will be our only relief between monitoring the cold front and the transition to monitoring the tropics. Tropical Storm Helene is forecast to make landfall as a major hurricane on Thursday evening. While the center and worst of the storm itself is forecast to move east of us, Helene is forecast to be very large, thus its impacts will be felt well beyond the center of the storm. For the TN Valley, we will begin to transition into Helene`s influence Thursday during the day. Rain chances and wind speeds will gradually pick up as Helene pushes north. Current forecast has wind gusts 20-30 MPH from Thursday during the day through Friday evening. NE AL overnight on Thursday will see the highest gusts. While current forecast does not warrant a Wind Advisory, it would still be a good idea to bring in loose objects. Rainfall will be our main concern as Helene moves through. Current forecast supports widespread rain totals of 2-5 inches of rain from Wednesday night through Saturday morning. While this amount alone is likely manageable, we have two concerns regarding the rainfall forecast. The first is that this rain is in addition to the 2-4 inches of rain we are expecting with the cold front from Tuesday (today) into Wednesday. It is very likely that soils will be very saturated by the time tropical rain from Helene gets here and make NE AL much more prone to flooding than it otherwise would be. The second concern related to how Helene will interact with the upper level low. As Helene pushes NE, the upper level low is forecast to retrograde across our area. This will place us squarely between the upper low and Helene, creating an enhanced area of convergence as both will be contributing to SE flow. SE flow will continue to pull in warm, moist tropical air and could support an additional threat for very efficient rainfall production. The impacts from this could lead to an increased flash flooding threat Friday morning, yet this threat materializing remains uncertain. We will be monitoring how both of these concerns play out over the next several day yet the bottom line up front front is concerns for flash flooding and river flooding from Helene with our area of highest concern being NE AL. Make sure to have multiple ways to receive warnings. Rain will continue for most of the day on Friday yet chances will quickly drop off Friday evening as Helene continues on her northward journey. Lingering SE flow will support a low chance of rain through the remainder of the short term but the flash flooding threat will likely have ended. && .LONG TERM... (Friday through Monday) Issued at 233 AM CDT Tue Sep 24 2024 The forecast going into the Long Term portion will of course be dependent on the eventual track of the tropical system, but the rainfall impacts to the area may transition more to the upper low over the Mid South/lower MS Valley regions as opposed to the remnant tropical system exiting to the ENE. Medium chances for showers/tstms (30-50%) are expected on Fri, as the upper low begins to drift eastward. However, given the slower movement of this feature, rain chances look to taper off this weekend to around 20-30%. In fact, any additional rainfall looks to remain as showers, although an isolated storm cannot be ruled out Sun afternoon. With less cloud cover/rainfall, highs this weekend look to climb back into the lower 80s/near 80F. Those rain chances increase slightly on Mon, as the upper low begins to lift into the OH Valley area. Highs on Mon also look to trend more in the upper 70s/near 80F. Lows this weekend and into next week look to remain in the lower/mid 60s. && .AVIATION... (00Z TAFS) Issued at 638 PM CDT Tue Sep 24 2024 VFR conditions continue at both KMSL and KHSV with vicinity thunderstorms through the overnight hours. Wednesday morning, ceilings and visibilities begin to decrease and MVFR to IFR conditions are forecast to occur as a result. With continued thunderstorm chances, AWWs will likely be needed during this TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...RAD SHORT TERM....RAD LONG TERM....09 AVIATION...HC