Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 13 2023 20:04:13 ACUS01 KWNS 132004 SWODY1 SPC AC 132002 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0302 PM CDT Sat May 13 2023 Valid 132000Z - 141200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM IOWA INTO CENTRAL ILLINOIS... ....SUMMARY... Thunderstorms associated with a few tornadoes, wind damage and large hail remain possible this afternoon and evening from Iowa into central Illinois. Isolated strong to severe storms are also possible across southern Oklahoma and East Texas as well as the eastern Virginia/North Carolina border vicinity. ....IA into the mid MS Valley... The Slight Risk across IA has been expanded slightly to the west and trimmed from the northeast, based on the location of ongoing convection and an outflow-reinforced surface boundary that is expected to move little during the rest of the afternoon. The environment remains only marginally favorable for supercells, but storms near the boundary may continue to pose a threat for at least brief tornadoes, in addition to isolated hail and gusty winds. Farther south, a storm cluster is ongoing from near St. Louis into parts of central IL. This cluster may continue to pose a threat for isolated severe hail/wind and possibly a brief tornado as it moves eastward this afternoon, and the Slight Risk has been expanded slightly southeastward. Renewed development along the remnant outflow cannot be ruled out back into east-central/northeast MO, which could also pose at least an isolated severe threat later this afternoon into the evening. ....Central/southern OK...ArkLaTex...East TX... 2% tornado probabilities have been confined to parts of southwest/central OK and north TX, in closer proximity to ambient surface vorticity near an MCV and associated weak surface low. Otherwise, no changes have been made to the Marginal Risk. See the previous discussion below. ....VA Tidewater into northern NC... No changes have been made to this area, see the previous discussion below for more information. ...Dean.. 05/13/2023 ..PREV DISCUSSION... /ISSUED 1115 AM CDT Sat May 13 2023/ ....IA into the Mid MS Valley... Recent surface analysis places a low about 30 miles northwest of OFK in far northeast NE. A cold front extends southward from this low through central KS and then back southwestward from north-central trough southwest OK. Surface pattern east of the low is a bit more complex, with a warm front extending from the low southeastward across southwest IA and into north-central MO. This warm front intersects a residual stationary boundary near DSM, with this stationary boundary continuing eastward across the OH Valley. The surface low is forecast to make modest eastward progress throughout the day, with the warm front continuing to move northward as well. However, the presence of the stationary boundary may impeded the northern progression of the warm front somewhat. Expectation is a corridor or mid to upper 60s dewpoints to extend from east-central MO/southern IL northwestward through central IA. This corridor will likely be south of the warm front, but east of dryline-like boundary that is expected to mix eastward with time. Moderate buoyancy is anticipated within this corridor as well, contributing to likely thunderstorm development as the boundary moves eastward. Southeasterly surface winds will beneath modest westerlies will contribute to moderate deep-layer vertical shear and the potential for more organized storm structures capable of all severe hazards across IA. Strong low-level buoyancy (i.e. 0-3 km MLCAPE greater than 150 J/kg) and low-level vorticity throughout the corridor of southeasterly winds could increase what would otherwise be a low probability tornado risk given anticipated shear magnitudes. Farther south, surface winds will be weaker with a more outflow-dominant storm structure anticipated. Here, some clustering is also possible, with storms then forward-propagating into west-central IL. ....Central/Southern OK...Arklatex...East TX... Widespread thunderstorm development is anticipated this afternoon from central OK eastward into the Arklatex and East TX amid the tropical air mass in place. Vertical shear is weak, limiting storm organization and the overall severe potential. Even so, a few water-loaded downbursts and maybe even a tornado or two remain possible. This low-probability tornado threat appears maximized across southern OK, where greater low-level vorticity is expected. ....VA Tidewater...Northeast NC... An upper trough is rotating quickly southeastward into New England, with a cold front sagging southward across WV/VA. This boundary will move into a relatively moist airmass over southern VA this afternoon, resulting in thunderstorm development. Strengthening westerly flow aloft and relatively steep boundary-layer lapse rates may result in a few strong wind gusts in the more intense cells. Activity will move into northern NC this evening before weakening. $$ = = = 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) .