Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Sep 04 2024 20:00:18 ACUS01 KWNS 042000 SWODY1 SPC AC 041959 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Wed Sep 04 2024 Valid 042000Z - 051200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY... ....SUMMARY... Isolated strong to severe thunderstorms capable of gusty winds and hail may occur this afternoon and evening across parts of the central Rockies into the northern/central Plains and upper Mississippi Valley. ....20Z Update... The forecast remains on track, and no appreciable changes were made to the outlook with this update. Isolated thunderstorms are developing/spreading eastward across the central Rockies this afternoon -- ahead of a positively tilted midlevel trough moving across the region. The strongest storms will be capable of producing marginally severe hail and isolated severe gusts. For additional details, see MCD #2047. Across the central Plains into the Upper MS Valley, severe-thunderstorm potential is more uncertain along/behind the cold front this evening into the overnight hours. However, given the potential for isolated instances of severe hail and locally strong/damaging gusts, the Marginal Risk has been maintained across this area. Farther east, clusters of thunderstorms are tracking westward across the central Gulf Coast, in an environment characterized by 2+ inch PW and pockets of diurnal heating/boundary-layer destabilization. Given some banded convection here -- aided by enhanced low-level easterlies -- a couple water-loaded downbursts will be possible. Overall, the severe threat still appears too localized/marginal for 5-percent severe wind probabilities. ...Weinman.. 09/04/2024 ..PREV DISCUSSION... /ISSUED 1124 AM CDT Wed Sep 04 2024/ ....Central Rockies into the central High Plains... Recent satellite imagery reveals a broad shortwave trough currently moving through southern ID and northern NV/UT. This shortwave trough and accompanying cold mid-level temperatures are forecast to continue eastward throughout the day, progressing across WY and northern CO. Modest buoyancy, fostered mainly by cooling mid-level temperatures, is anticipated across WY and adjacent parts of northern CO as the shortwave trough progresses through. Thunderstorm development is expected as the large-scale ascent attendant to the shortwave trough interacts with this buoyancy during the afternoon. Moderate mid-level westerlies will accompany this shortwave trough as well, with the resulting increase in vertical shear supporting the potential for a few more organized/persistent storms. Initially more cellular development across the higher terrain could pose a risk for isolated hail, particularly across south-central WY and north-central CO where the best overlap between the stronger shear and cold mid-level temperatures is expected. Damaging wind gusts are possible as well, particularly as the storms reach the lower elevations of central High Plains where a deeply mixed boundary layer will be in place. ....Central Plains into the Upper MS Valley... Recent surface analysis places a low over southeast ND, with weak troughing extending southwestward from this low in east-central CO. The primary cold front is west of this surface trough, extending from the low over southeast ND into more of northwest SD and adjacent northeast WY. The surface low is forecast to progress east-southeastward throughout the day, reaching south-central MN by late tonight. The attendant cold front is expected to push southward during the same period, progressing through much of NE by early Thursday morning. Warm mid-level temperatures should preclude thunderstorm development along the surface trough during the afternoon and evening. A few isolated storms are possible during the evening behind the front as the shortwave trough ejects out into the central Plains. Additional thunderstorm development is expected overnight/early Thursday morning across the Upper MS Valley, with some isolated hail possible within the strongest storms. $$ = = = 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) .