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Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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314 FXUS64 KHUN 151925 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 225 PM CDT Thu Aug 15 2024 ...New NEAR TERM, SHORT TERM... .NEAR TERM... (Tonight through midday Friday) Issued at 203 PM CDT Thu Aug 15 2024 The forecast for Northern AL and Srn Middle TN hasn`t changed much in the past 24hrs; we still have a stalled sfc frontal boundary draped from the ArkLaMiss SE into the Nrn GOMEX, with high pressure in control aloft across the area. This ridge will set the stage for the change in pattern expected for our area as it retrogrades W, allowing our area to be in more NW flow. This will allow MCS activity upstream to divert SE toward the local area on Friday and again on Saturday. Before we get to that just yet, the rest of today will be warm but heat index values will remain below Advisory criteria this afternoon. Any convection today will be relegated to our far Ern zones on the edge of the ridge. Tomorrow ahead of the developing storms, a Heat Advisory will be issued from 11am to 5pm for Heat Index values in the 105-107F category along and west of a Lincoln TN/Madison/Morgan/Cullman AL Counties line. The impacts from the heat will dissipate when the storms arrive toward the end of that timeframe. Daytime highs will top out in the 95-98F range. && .SHORT TERM... (midday Friday through Sunday) Issued at 203 PM CDT Thu Aug 15 2024 The threat for storms tomorrow is the big question, and moreso where convection will develop. An MCS ongoing upstream of us tonight will dive SE tonight and eventually dissipate. This will throw an outflow boundary toward N AL/Srn Middle TN. The uncertainty in this portion of the forecast is precisely where this boundary ends up, and therefore, pinpoints the area that will have convective initiation first tomorrow. Most HIRES models show a wide range of time of arrival of the storms; as early as 14z or as late as 21/22z. The best consensus shows convection firing up right on top of us between 18-20Z and then scooting off to the SE thru the evening. Like yesterday, thermodynamic elements support a gusty to damaging wind threat (50-60mph) with these storms, combined with low level lapse rates between 7-8C/km. When these storms form, they`ll rapidly grow with the potential to produce wind gusts quickly. Heavy rainfall is another threat tomorrow with PWats in the 90th percentile for climatology. Widespread 1-1.5" rainfall amounts seem reasonable, with isolated higher amounts in excess of 2" less likely, but possible in areas where storms slowly move. Hail is also a possibility, but I think with the excess moisture in the atmosphere, enhanced melting will help keep this threat at bay. Saturday now holds another shot at strong/severe storms and heavy rainfall. Like Friday, an MCS upstream of the local area will dive SE Friday night into early Saturday morning. Unlike Friday, some light rain may overspread the area as the MCS decays early Saturday morning. This will delay any redevelopment until later in the afternoon/early in the evening on Saturday, making for storms more likely after ~21z the most probable scenario then. Regarding the thermodynamics Saturday, a similar atmosphere will be in place with perhaps a bit more shear (30-35kts) and instability (with the later arrival time/peak heating), translating to a 50-60mph wind threat and more locally heavy rainfall. This activity should linger through midnight or a little after before the same scenario is repeated Sunday, though thankfully south of our CWFA (Birmingham and points south). The cold front will push through our CWFA overnight Saturday into Sunday, with rain chances finally dwindling and more calm and dry weather expected to start the new work week. && .LONG TERM... (Sunday through Wednesday) Issued at 419 AM CDT Thu Aug 15 2024 The upper trough centered just to our east will continue to dig south through the second half of the weekend, and will lead to a cooler, drier pattern to start the work week. Will keep low chances (20-30%) for showers/storms Sunday with the cold front expected to push south through the area Sunday afternoon/evening. By then, expect the better strong/severe thunderstorm environment to be to our south where the axis of better moisture lies. Dry weather will return by late Sunday, and northerly flow will begin to advect cooler temperatures into the area. The remainder of the long term forecast looks very nice for mid to late August, with daily highs in the 80s and lows in the low to mid 60s. High pressure will help us maintain a dry forecast through Wednesday. && .AVIATION... (18Z TAFS) Issued at 1236 PM CDT Thu Aug 15 2024 VFR conditions will prevail through the duration of the TAF period. After sunrise tomorrow winds will shift from SE to SW with a slight increase in winds speed to around 6 KTS. There is a low chance of rain and storms from 12-18Z tomorrow however confidence was too low to include in the TAF. In confidence increases rain and thunder will be added to the TAF during additional issuances. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Heat Advisory from 11 AM to 5 PM CDT Friday for ALZ001>007-016. TN...Heat Advisory from 11 AM to 5 PM CDT Friday for TNZ096. && $$ NEAR TERM...12 SHORT TERM....12 LONG TERM....25 AVIATION...RAD