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Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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084 FXUS64 KHUN 290233 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 933 PM CDT Fri Jun 28 2024 ...New NEAR TERM... .NEAR TERM... (Rest of tonight) Issued at 933 PM CDT Fri Jun 28 2024 Showers have largely come to an end across the area with the loss of diurnal heating, but sfc temperatures are slow to cool this evening. Sky cover will start as mostly clear tonight but do expect to see an increase in cloud cover from east to west through the morning hours. This combined with southerly flow will help keep temperatures on the warmer side, only falling into the low to mid 70s. The increasing clouds should also help mitigate any fog concerns, but will monitor through the overnight hours just in case any patchy fog does develop. && .SHORT TERM... (Saturday through Sunday night) Issued at 202 PM CDT Fri Jun 28 2024 Latest model consensus suggests that a zone of subtle low-level streamline confluence (likely related to the transition to southwesterly flow ahead of an approaching cold front) will continue to serve as a focusing mechanism for the development of showers and thunderstorms through much of the day on Saturday. Although there is uncertainty regarding the precise location of this boundary, we have placed our highest POPs across the southeastern portion of the CWFA given indications of southwesterly steering flow in the lower/middle troposphere that will support east- northeastward movement of showers and thunderstorms with time. With indications of a typical early summer shear and thermodynamic profile (featuring MLCAPE in the 1500-2500 J/kg range), strong outflow winds (perhaps up to 40-50 MPH) and frequent lightning will be concerns with the strongest storms. Although morning low stratus clouds and afternoon convective debris clouds will have an impact on high temps, heat indices will still manage to reach 98-102F for most of the valley (and perhaps close to 105F in larger urban locations). Present indications are that afternoon convection will diminish quickly once again around sunset, providing for a warm/humid evening and perhaps early development of fog across portions of northeast AL that experience wetting rains during the afternoon. By early Sunday morning, we will be monitoring the progress of thunderstorms to our northwest, which should initiate along a cold front dropping into southeastern KS/southern MO late in the afternoon. Most of the 12Z CAMs and global models indicate that this convection may expand in coverage and spread southeastward with time early Sunday morning, perhaps sending an outflow boundary southeastward into the TN Valley after Midnight. Should this occur, redevelopment of a few showers and thunderstorms may occur during the early morning hours. However, the most likely scenario is for redevelopment of convection to occur on Sunday afternoon as the actual synoptic cold front shifts southward into the local area. Although NW flow aloft will increase a bit by Sunday as the subtropical ridge begins to amplify across the southern Plains, shear will remain fairly weak but may be sufficient for a few strong storms given comparable levels of instability. Showers and thunderstorms should end from NW-to-SE Sunday evening with frontal passage, and a drier airmass will begin to spread into the region by Monday morning providing for cooler lows in the m-u 60s. && .LONG TERM... (Monday through Thursday) Issued at 1258 AM CDT Fri Jun 28 2024 Excessive heat will be the main story going into the latter half of the forecast period. A large upper ridge axis over the Plains states will begin to gradually move eastward heading into the new work week. At the sfc, high pressure will build eastward across the upper Midwest/Great Lakes regions in the wake of a departing cold front to the south. Lingering showers/tstms will also taper off to the south providing for a dry forecast at least thru Mon night. The passing frontal boundary should also translate into slightly cooler temps, with lows Sun night in the upper 60s/near 70F, before temps rebound into the upper 80s/near 90F later in the day Mon. The upper ridge pattern will then become entrenched across the Gulf Coast region starting Tue, with afternoon temps climbing into the mid/perhaps upper 90s. High pressure moving into the northern/mid Atlantic Basin will also result in SFC flow veering to the SE/S, thereby ushering moisture back into the central TN Valley. Max heat indices likewise may climb near/above 105F, especially on July 4th. Subsequently, Heat Advisories may be needed Wed and Thu. In addition to the excessive heat, diurnally driven showers/tstms (around a 20-40% chc) are possible starting Tue. Any convective activity will likely be pulse driven given ample buoyant energy, but little in the way of deep layer shear. && .AVIATION... (00Z TAFS) Issued at 652 PM CDT Fri Jun 28 2024 VFR conditions have prevailed this afternoon into this evening, despite a few isolated showers. This activity should come to an end shortly with the loss of diurnal heating, but some light to moderate rain may briefly impact KHSV within the next hour. Additional showers/storms are forecast tomorrow, and have added PROB30 groups in for showers and storms during the morning and afternoon hours. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...25 SHORT TERM....70 LONG TERM....09 AVIATION...25