Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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103 FXUS64 KHUN 080937 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 437 AM CDT Wed May 8 2024 ...New NEAR TERM, SHORT TERM, LONG TERM... .NEAR TERM... (Today) Issued at 437 AM CDT Wed May 8 2024 Conditions remain warm, humid and dry across the TN Valley early this morning, with mild temperatures in the l-m 70s as of this writing. We are currently watching two areas of convection, with the first located across KY (which initiated late yesterday evening in the vicinity of a surface trough/remnant dryline sagging southeastward into the OH Valley). Present indications are that this activity should spread generally eastward and will not have a direct impact on our CWFA through 12Z. The second area of convection (currently across eastern AR) also developed late yesterday evening in the vicinity of a separate surface trough extending southeastward into northern MS/central AL from an area of low pressure dropping southeastward into western OK. Latest high-resolution model data suggests that this activity will gradually weaken as it shifts east-northeastward through 12Z and should also not have a direct impact on our CWFA aside from providing high-level anvil debris clouds. Over the course of the morning, the surface trough to our south will lift northward through the TN Valley and should become the effective warm front of the surface low to our west as it ejects northeastward into central MO by 0Z Thursday. Widespread severe thunderstorms are expected along and north of this boundary during the afternoon hours, which will likely lie along an axis from the Ozarks east-southeastward into the Smoky Mountains. However, aside from a few morning showers that may occur as the warm front tracks northward, our region should remain capped and dry for much of the day, with highs in the mid 80s. That said, we will need to keep any eye to the southwest late this afternoon, as a few warm sector supercells may develop across northeastern MS. && .SHORT TERM... (Tonight through Friday night) Issued at 437 AM CDT Wed May 8 2024 The forecast for tonight remains rather complicated, largely due to the weak nature of deep-layer forcing for ascent across our region and fact that thunderstorms will be tied to processes occurring well to our northwest. However, at this point, the most likely scenario seems to be that the risk for severe thunderstorms across our CWFA may increase as early as the 0-3Z timeframe, either from isolated cells that develop to our southwest late this afternoon and spread northeastward, or with development of new storms along outflow from widespread convection to our north that may drift southwestward into southern TN/northeast AL. A separate MCS may also evolve this evening out of convection that develops late this afternoon along the cyclones cold front (extending from the low southwestward into north central TX). Precisely where this system will develop and track is still uncertain, but present indications are that it would not arrive in our forecast area until the 6-9Z timeframe at the earliest (and perhaps as much as 3-6 hours later than this). The combination of 40-50 knot WSW flow aloft and steep mid-level lapse rates atop a moist boundary layer (featuring dewpoints in the u60s-l70s) will support a risk for large hail and damaging winds, with a modest SW low-level jet of 25-35 knots providing sufficient shear in the 0-3km layer for a lower-end risk for tornadoes. Several CAMs suggest that convective outflow will eventually outrun the MCS as we move forward in time, with extensive trailing stratiform rain and embedded thunderstorms expected to gradually spread southeastward and out of the region by 18Z Thursday. The actual cold front should shift southeastward late Thursday afternoon and exit the forecast area during the evening hours, as another broad complex of thunderstorms tracks eastward along the central Gulf Coast. Although redevelopment of showers and storms along the cold front appears unlikely in our region, we have indicated a low-medium chance POP on Thursday night to account for some uncertainty regarding the path of the MCS to our south and potential for the northern edge of the stratiform rain shield to graze our region. In the wake of any lingering morning precipitation on Friday, dry conditions are currently predicted on Friday and Friday night. However, with a longwave trough expected to cross the region on Friday and a trailing vort max digging southeastward into the region Friday night, a fair amount of mid-level cloud cover is anticipated (and perhaps even a few very light showers). These two periods will mark the coolest of the forecast, with highs in the u60s-m70s Friday and lows in the u40s-l50s Friday night. && .LONG TERM... (Saturday through Tuesday) Issued at 437 AM CDT Wed May 8 2024 A generally dry weather pattern will continue across the region this weekend. However, a clipper system diving southeastward into the western Great Lakes will send a reinforcing cold front through the region on Saturday, perhaps bringing a few light showers to locations north of the TN River. Chances for rain will begin to slowly return to the region as early as Monday, which is when a series of lower-latitude troughs may initiate the development of one or more areas of low pressure across the western Gulf of Mexico that would shift northeastward early next week. Due to indications of a modifying low-level airmass across the TN Valley, instability will gradually increase as we move forward to Tuesday, with a low chance for thunderstorms apparent as well. && .AVIATION... (06Z TAFS) Issued at 1248 AM CDT Wed May 8 2024 VFR conditions are currently observed at the HSV/MSL terminals, but there are indications that low stratus clouds will develop within the very moist boundary layer, providing MVFR cigs arnd 1500 ft AGL btwn 9-15Z. As the low stratus layer disperses later this morning, a rapidly destabilizing airmass will support the development of sct-bkn Cu, with the risk for a few warm sector TSRA increasing in the 21-03Z timeframe. Although probabilities for more a more widespread coverage of storms will increase with time as we approach the end of the TAF period, confidence is not high enough to introduce anything more than an additional PROB30 group attm. Prevailing sfc flow will remain from the SSW, with sustained speeds of 5-10 knots (and gusts of 15-20 knots this aftn). && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70/DD SHORT TERM...70/DD LONG TERM...70/DD AVIATION...70/DD