Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 02 2023 05:46:27 ACUS02 KWNS 020546 SWODY2 SPC AC 020544 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Wed Aug 02 2023 Valid 031200Z - 041200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE CENTRAL HIGH PLAINS... ....SUMMARY... Severe thunderstorms producing large hail and damaging gusts are expected across portions of the central High Plains Thursday afternoon and evening. Additional strong storms are possible across parts of the Great Lakes/Northeast and the Tennessee Valley vicinity. ....Synopsis... The mean upper flow regime on Thursday will be characterized by a ridge oriented over the High Plains and a trough across the eastern third of the CONUS. A midlevel shortwave trough is expected to migrate through the upper ridge from eastern UT/western CO into the northern/central High Plains. Across the east, several shortwave perturbations are expected to move through the upper trough. One of these impulses will shift east across the Great Lakes toward the St. Lawrence Valley vicinity. Another impulse, convectively enhanced by a storm complex in the Day 1/Wed time frame, will move across the TN Valley vicinity. These three features will focus strong to severe thunderstorm potential on Thursday/Thursday evening. ....Central High Plains vicinity... Mid/upper westerly flow around 30-40 kt is forecast as the midlevel shortwave trough ejects eastward through the afternoon/evening. East/southeasterly low-level flow will maintain 60s F surface dewpoints across the region, supporting a corridor of 1500-3000 J/kg MLCAPE. Effective-shear magnitudes around 35-45 kt will support organized cells capable of large hail initially. Steep low-level lapse rates and boundary-layer mixing to around 1-2 km also will support strong outflow gusts. With time, clustering and consolidating outflows will foster development of an MCS across western NE/northeast CO/northwest KS during the evening. Damaging wind potential will accompany this activity into the early overnight hours. ....TN Valley vicinity... Showers and thunderstorms will likely be ongoing Thursday morning somewhere from southeast MO into Middle TN. This activity will likely pose mainly a heavy rain threat initially before some decrease in precipitation. However, cloudiness will likely continue across parts of KY/TN, becoming less with southward extent. This will result in a differential heating boundary somewhere in the vicinity of Middle TN into northern AL/GA. Strong northwesterly mid/upper flow for this time of year will overlap a most and unstable airmass. Convection is expected to develop during the afternoon along remnant outflow/differential heating zone. Organized clusters may grow upscale into an MCS moving east/southeast across parts of TN into northern MS/AL/GA and vicinity, and pose a damaging-gust risk. Given the presence of a surface boundary and increasing winds with height, some risk for a tornado or two also is evident as SRH increases and low-level hodographs become enlarged through the day. Importantly, convection in the Day 1/Wed time period continuing into Thursday morning results in some uncertainty concerning where exactly this differential heating boundary will reside. This will impact the eastward extent of severe potential, while weakening vertical shear will limit southward extent. Nevertheless, confidence has increased sufficiently to include Marginal risk (Level 1 of 5) severe probabilities, and upgrades may be needed in subsequent outlooks. ....Great Lakes/Northeast vicinity... A shortwave impulse embedded in the larger-scale eastern trough will move across the Great Lakes much of the period. A belt of 30-40 kt midlevel flow will overlap a seasonally moist boundary layer ahead of a south/southeast-advancing cold front. MLCAPE generally less than 1500 J/kg is forecast amid modest midlevel lapse rates. Low-level flow will be fairly light, but speed shear will support effective-shear magnitudes around 25-35 kt. Forecast soundings show elongated/straight hodographs, and marginally severe hail will be possible with stronger updrafts. Strong heating will result in steep low-level lapse rates, and strong outflow winds also will be possible. Some potential for a westward expansion of the Marginal risk (level 1 of 5) into eastern WI is possible, but uncertainty regarding convective coverage and a more conditional risk with westward extent precludes probabilities at this time. ...Leitman.. 08/02/2023 $$ = = = 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .