Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 17 2023 17:31:15 ACUS02 KWNS 171731 SWODY2 SPC AC 171729 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Thu Aug 17 2023 Valid 181200Z - 191200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF NEW ENGLAND AND ARIZONA... ....SUMMARY... Isolated severe thunderstorms with a risk for damaging gusts and perhaps a tornado or two will be possible during the day across portions of New England on Friday. Storms capable of isolated severe gusts will also be possible across parts of Arizona. ....Synopsis... A seasonably deep/strong upper-level trough will move across the Northeast and Mid Atlantic regions on Friday. An associated surface low will move eastward across Quebec, as a trailing cold front moves from the upper Great Lakes into New England through the day. Farther west, a mid/upper-level low will remain nearly stationary off of the California coast. A mid/upper-level shortwave trough and associated surface low will move across the Canadian Prairies, as an attendant cold front moves into the northern Plains. ....Northeast... Multiple rounds of convection are possible across parts of the Northeast/New England on Friday. The initial morning to early afternoon round may be capable of locally damaging gusts and perhaps a tornado or two, with a more isolated threat later Friday afternoon along/ahead of the cold front. One or more storm clusters will likely be ongoing Friday morning somewhere from northern NY into southern New England. Strong deep-layer flow associated with the approaching upper trough will support sufficient effective shear for organized convective elements within these clusters. The strongest buoyancy (with MLCAPE generally 500-1000 J/kg during the morning) is expected near/south of a northward-advancing warm front across southern New England, with weaker instability extending northward into parts of VT/NH. The morning threat will likely be maximized near/south of the warm front, where line-embedded supercells and/or shorter-lived mesovortices will support potential for locally damaging gusts and perhaps a tornado or two, within an environment of favorable low-level shear/SRH. Depending on the extent of heating/destabilization that can occur across southern New England prior to storm arrival, higher severe probabilities may eventually be needed. In the wake of early-day convection, redevelopment along/ahead of the cold front will be possible during the afternoon. Coverage and intensity of convection associated with the cold front remain uncertain, with storms potentially struggling to mature due to generally weak instability and a midlevel dry slot overspreading the region. However, a few strong to locally severe storms will be possible within this frontal regime, with a threat of locally damaging gusts and small to marginally severe hail. ....Arizona... Scattered to numerous thunderstorms are expected Friday from AZ into southern NV/UT, as moisture continues to increase east of the nearly stationary upper-level trough off of the CA coast. Modest southerly midlevel flow will support the potential for loosely organized, north to northwesterly moving clusters during the afternoon and evening. Localized severe gusts will be possible where somewhat stronger preconvective heating/destabilization occurs, which currently appears most likely across the lower elevations of southern/central AZ. Small hail and gusty winds will also be possible into northern AZ, though coverage of any severe threat remains more uncertain across this area. ....Montana... Widely scattered high-based convection is expected across parts of MT Friday afternoon and evening. Hot, deeply mixed boundary layers will support the potential for localized severe gusts, though the threat appears too disorganized and unfocused for severe-wind probabilities at this time. ...Dean.. 08/17/2023 $$ = = = 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) .