Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 15 2024 19:57:54 ACUS01 KWNS 151957 SWODY1 SPC AC 151956 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Thu Aug 15 2024 Valid 152000Z - 161200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL OK TO THE MID MS VALLEY... ....SUMMARY... Scattered severe thunderstorms are possible across parts of the Midwest through tonight. Severe gusts capable of wind damage and large hail are the primary risks with the stronger thunderstorms. A cluster of storms is ongoing across eastern Nebraska and will move into an increasingly unstable environment across Iowa later this afternoon and this evening. Have expanded the slight risk farther north into Iowa to account for this threat. See MCD #1907 for more discussion of this threat. Elsewhere, the forecast remains on track. Thunderstorm development appears imminent along a frontal boundary in Oklahoma within the next 1 to 2 hours. A somewhat similar environment exists farther southwest across portions of northwest Texas and the Texas Panhandle. However, slightly warmer temperatures around 500mb may limit updraft intensity somewhat and thus mitigate a greater severe weather threat. A few storms have developed over the higher terrain in central Idaho and southwest Montana. These storms may pose some severe wind threat as they move northeast. However, instability is quite weak (100-250 J/kg MLCAPE) and should keep any threat mostly isolated. A few large hail and severe wind gusts have occurred across New Hampshire this afternoon and a few additional strong to severe storms may develop in the region, in addition to the ongoing cluster now in northern Massachusetts. This threat should persist through early evening before waning near or shortly after sunset. ...Bentley.. 08/15/2024 ..PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Aug 15 2024/ ....Mid MS Valley this afternoon/evening... The remnants of overnight convection, and an associated/lead shortwave trough, are moving across southern MO/IL. Though these storms will likely weaken through midday, a diffuse outflow/differential heating zone may help focus additional thunderstorm development this afternoon. Southern MO to southern IL will be along the southern fringe of the stronger midlevel flow, where a mix of multicell clusters and possibly a supercell or two capable of producing damaging winds (60-70 mph) and isolated large hail (1-1.5 inches in diameter) will be possible later this afternoon/evening. The primary midlevel shortwave trough will progress eastward from NE/SD toward the upper MS Valley by tonight, in conjunction with a surface cold front. Weak, ongoing convection across north central and northeast NE reflects the zone of ascent spreading east-southeastward through the afternoon, toward the destabilizing warm sector in the wake of overnight convection across northern MO/southern IA. Though timing is still a bit uncertain, thunderstorm development appears probable late this afternoon or this evening across eastern NE and especially near the MO/IA border. Relatively long/straight hodographs, midlevel lapse rates near 7.5 C/km and MLCAPE in excess of 2000 J/kg will support supercells capable of producing large hail (1-2 inches in diameter) and damaging gusts (60-75 mph). Some upscale growth into a cluster may also occur as the storms spread east-southeastward toward IL tonight. ....OK this afternoon/evening... Strong surface heating is ongoing across central OK along a weak pre-frontal trough. Mid-upper flow will be weak this far southwest, but deep mixing with surface heating will contribute to steep low-level lapse rates and MLCAPE of 1500 J/kg or greater with minimal convective inhibition. Scattered thunderstorms are expected along this trough by mid-late afternoon, when isolated damaging downburst winds (60-75 mph) will be possible. ....New England this afternoon... To the west of a closed low over Nova Scotia, an embedded shortwave trough is rotating southward over New England with ongoing convection in southwest ME and NH. Surface heating/destabilization on the western/southern fringes of the ongoing storms will likely contribute to additional thunderstorm development this afternoon. Moderate buoyancy and steepening low-level lapse rates, as well as cool midlevel temperatures (-14 to -15 C at 500 mb), will support the potential for isolated wind damage with 45-60 mph gusts and isolated hail approaching 1 inch in diameter with multicell clusters. See MD #1557 for additional information. ....Northern Rockies this afternoon/evening... A midlevel trough will eject east-northeastward over ID/southwest MT/extreme northwest WY through this evening. Steep lapse rates and modest PW (near or less than 0.75 inches) will support high-based thunderstorm development this afternoon in the zone of ascent preceding the midlevel trough. Strong outflow gusts (50-60 mph) will be the main concern. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .