Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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419 FXUS64 KHUN 191955 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 255 PM CDT Wed Jun 19 2024 ...New NEAR TERM, SHORT TERM... .NEAR TERM... (Tonight) Issued at 255 PM CDT Wed Jun 19 2024 A large area of high pressure is currently centered off the eastern seaboard and extends west into the Mid-Atlantic area. This continues to bring the worst of the heat over the eastern U.S. to northeastern portions of the country. Further south, quite a bit of mid/high cloud cover is helping to keep conditions a bit cooler. Here over the Tennessee Valley, this cloud cover has become more widespread over the last few hours and has kept temperatures in the lower to mid 80s. Not sure we will see more breaks in cloud cover later this afternoon, so will lower highs a bit to keep forecast closer to what observations would suggest later today. Likely highs will only reach the mid to upper 80s. Most guidance suggest that the surface high doesn`t move much overnight. This should keep enough of a pressure gradient over the area to keep winds around 5 mph, except in sheltered valley locations (could be light and variable there). Given prevalent low level advection from the east, not expecting dewpoints to change much. Guidance continues to show cloud cover dissipating later tonight. Winds should help keep low temperatures up a bit though. This should allow temperatures to only drop into the 65 to 70 degree range (lower valeus likely in spots that are sheltered valley locals). && .SHORT TERM... (Thursday through Saturday) Issued at 255 PM CDT Wed Jun 19 2024 During the day on Thursday, the center of the upper level ridge associated with the surface high shifts southwest into the Tennessee Valley. Not confident models are handling cloud cover caught up in this ridge, but kept with low sky coverage guidance is presenting at this time. It should get hotter again in response to the building upper ridge Thursday afternoon, but how much is the question. Given the uncertainty with cloud cover, the forecast only included highs in the 90 to 95 degree range mostly. This should keep heat index values 95 to 100 degrees. The upper ridge drops further southwest and sets up right over the area late Thursday night through Saturday. With that feature right over the area and little cloud cover expected Friday and Saturday, these may be our hottest days during that period. Highs on one or both of those days could climb into the mid to upper 90s. However, kept temperatures and heat index on the lower side on Friday again given uncertainty with cloud cover. By Saturday though, heat index values could climb just over 100 degrees again. && .LONG TERM... (Sunday through Wednesday) Issued at 355 PM CDT Wed Jun 19 2024 Guidance from the 12Z suite of global models suggests that a strong mid-level high will continue to be centered across the TN Valley at the beginning of the extended forecast period. Although this evolution will result in a gradual increase in NW flow aloft for the TN Valley. Given the a continued increase in 925 mb temperatures, thinking highs still could reach the mid to upper 90s again in some areas. However, confidence is low this will happen given some of the model guidance as subsidence weakens and possibly a weak shortwave approaches the area on Sunday. Thus, low chances of afternoon/evening showers and thunderstorms were introduced into the forecast. If highs do reach the mid/upper 90s, then heat index values could climb to between the 98-102F range with dewpoints in the 65 to 70 degree range. There is reasonably good agreement among the models that a weak cold front (attached to the northern stream trough) will drop southward through the region on Monday, and we have indicated our highest POPs for the extended period on this day. Frontal convection will likely end south of the TN River Monday evening, with the front expected to decelerate and become increasingly oriented in a NW-SE fashion to the west of the forecast area on Monday night/Tuesday. Although a slightly drier airmass may spread into the northeastern portion of the region, there is some uncertainty regarding precisely where the front will lie, and we have kept a low (~20% POP) intact for Tuesday. High temperatures will change little (if at all) in the wake of the front, but may be a couple of degrees cooler due to an increase in cloudiness both days. && .AVIATION... (18Z TAFS) Issued at 122 PM CDT Wed Jun 19 2024 VFR conditions are expected throughout the TAF period with on and off mainly high cloud cover over the next 24 hours. Wind gusts from the east will drop off this evening, but remain around 5 knots much of the night. This should keep fog at bay. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...KTW SHORT TERM....KTW LONG TERM....70 AVIATION...KTW