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Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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364 FXUS64 KHUN 141927 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 227 PM CDT Wed Aug 14 2024 ...New NEAR TERM, SHORT TERM... .NEAR TERM... (Tonight) Issued at 226 CDT Wed Aug 14 2024 Aside from shower activity affecting NW AL this afternoon, much of the forecast for tonight revolves around humid conditions coming back to the area after a brief reprieve from it over the last few days. What convection is ongoing now will dissipate shortly after sunset this evening, with morning lows falling into the lower 70s. Some patchy fog is possible tomorrow morning, especially in locations that received some light rainfall today. && .SHORT TERM... (Thursday through Saturday) Issued at 226 PM CDT Wed Aug 14 2024 Low chances (10-20%) for showers and storms exist again on Thursday, with hit or miss convection around the area. The bigger story for tomorrow will be daytime highs and potential heat index values. Daytime highs tomorrow will top out in the middle 90s with HI values in the low 100s. The area is highlighted on the HeatRisk maps with a Moderate Heat Risk for Thursday, but this threat ramps up Friday ahead of the convection that may/may not impact Northern AL and Southern Middle TN. A Heat Advisory will likely be needed Friday (ahead of storms) for areas along/W of Interstate 65 with the HeatRisk map advertising Major impacts with daytime highs in the upper 90s and Heat Index Values at/above 105F (Heat Advisory Criteria). The bulk of the focus on the forecast package this afternoon revolves around this potential for strong/severe storms on Friday afternoon/evening (despite the threat for dangerous heat earlier in the day). There is some uncertainty of storms forming to the N of the local area ahead of a cold front sprawled across the OH Valley. Models indicate an outflow boundary from a remnant MCS pushing SE toward the area during Friday afternoon/evening. While the CAMS are notorious for dissipating MCS activity too prematurely, the atmosphere does have decent thermodynamic support for the threat of strong/severe storms during this time. MUCAPE north of 3000 J/kg combined with lapse rates approaching 8C/km should allow for anything that develops along the outflow boundary to grow rapidly, and with higher PW values in the 90th percentile for climatology, this poses a gusty/damaging wind and heavy rainfall threat. For this reason, we`ve messaged this to partners and in the public graphics this afternoon. Can`t discount a hail threat either during this time, but the thinking is that with the high moisture content in the atmosphere, this should enhance melting before it reaches the ground. Storms will move through the area into Friday evening, making way for a muggy start to the day Saturday. Morning lows will start out in the 72-76F range, climbing into the lower 90s (a few degrees lower than Thu/Fri thanks to cloud cover from recent convection). A cold front will be approaching the area at the end of the short term portion of the forecast, slated to enter the area Sat night. More details to follow in the Long Term section of the AFD from the midnight shift crew below... && .LONG TERM... (Saturday through Tuesday) Issued at 156 AM CDT Wed Aug 14 2024 An upper shortwave trough is shown to traverse the Ohio and Tennessee valleys to begin the long term. At the surface, anticipating the passage of a cold front overnight on Saturday, with high pressure moving into the region through early next week. There are some discrepancies with regards to the evolution of the upper trough (how far south the trough digs) and how quickly it moves east through the weekend and into early next week. This would affect how much the upper ridge to the west pushes into the Southeast. A drier forecast is anticipated with a more eastward nudge of the ridge. Otherwise, we`d be more under the influence of northwest flow aloft, which would be conducive for potential MCS activity (increased chances for showers/storms). Overall, we`ll continue to monitor model trends, but the forecast currently calls for low to medium chances (20-45%) of showers and storms on Saturday ahead of the cold front, with some low chances (20-30%) of showers and storms lingering into Sunday. We`ll need to keep an eye on Saturday, as models indicate that there will be sufficient instability and increasing bulk shear from the afternoon into the evening (ahead of the cold front) for stronger storm development. At this point, drier weather is then expected to take hold for early next week. Highs will generally hover between the upper 80s to lower 90s each day, with lows decreasing into the mid to upper 60s by Sunday night. The warmest day of the long term will be Saturday, as moisture remains elevated (dew points in the lower to mid 70s) for most locations during the day. While Heat Advisory criteria is not likely to be reached, it`ll still be warm. Heat indices are expected to reach the upper 90s to around 102 degrees and NWS HeatRisk outlooks our local area in a minor to moderate risk of heat-related illness. Ultimately, please make sure to stay hydrated and take frequent breaks in the shade if you have outdoor plans next Saturday. && .AVIATION... (18Z TAFS) Issued at 1239 PM CDT Wed Aug 14 2024 VFR conditions are expected at both KMSL and KHSV thru the TAF period. A few showers are in the vicinity of KMSL, but its a very low chance that one directly impacts the terminal. For this reason, retained the PROB30 for the afternoon, but confidence is low in this scenario. Patchy fog is possible at KMSL tomorrow morning with the rain in the local area today, but will reassess this with the 00Z TAF cycle. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...12 SHORT TERM....12 LONG TERM....26 AVIATION...25