Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 29 2023 20:01:31 ACUS01 KWNS 292001 SWODY1 SPC AC 291959 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Sat Jul 29 2023 Valid 292000Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST/MID-ATLANTIC...MID MISSISSIPPI VALLEY...AND NORTHERN/CENTRAL PLAINS... ....SUMMARY... Widely scattered to scattered severe thunderstorms with damaging winds are possible over southern New England into the Mid-Atlantic and Missouri through this evening. Large hail and strong to severe outflow gusts are also possible this evening into tonight across the central/northern High Plains. ....20Z Update... Severe probabilities have been adjusted across MO into southern IL/IN and western KY based on a persistent MCS moving east-southeastward over MO. Several damaging wind and multiple measured severe gusts have been noted with this cluster, and this should remain the primary severe threat through the rest of the afternoon. The northern extent of the wind threat should be constrained by a weak front/instability gradient extending across southern IL. See Mesoscale Discussion 1774 for more details. Otherwise, minor adjustments have been made to the Marginal/Slight Risk areas across New England and the Mid-Atlantic into the Carolinas based on recent observational and short-term model trends. No changes have been made to the Slight Risk across the northern and central High Plains. Greater confidence exists for convection to develop over the higher terrain of northern/central CO and spread eastward into the adjacent High Plains over the next couple of hours. Both large hail and severe wind gusts will be possible with any supercells that can be sustained. ...Gleason.. 07/29/2023 ..PREV DISCUSSION... /ISSUED 1114 AM CDT Sat Jul 29 2023/ ....Mid-Atlantic to southern New England through this evening... Overnight convection has largely dissipated over PA, with some convection persisting across NY from Lake Ontario eastward along a surface front that is moving slowly southward. A convectively-augmented midlevel trough and belt of 40-50 kt midlevel flow will continue eastward today over PA/NY, as an associated/weak surface cyclone likewise develops eastward. 12z regional soundings revealed poor midlevel lapse rates in the warm sector, but surface heating in cloud breaks will contribute to destabilization through the afternoon as temperatures warm into the 80s across southern New England and the 90s into VA/Mid-Atlantic. Scattered thunderstorms are expected to form by early-mid afternoon along the surface wind shift/front and along differential heating zones and spread eastward through this evening. MLCAPE of 1000-1500 J/kg, steepening low-level lapse rates and the increasing midlevel flow from west-to-east suggest that damaging winds will be the main threat with a mix of multicell clusters and some supercells this afternoon into this evening. Additional clusters/bands of storms are expected this afternoon from eastern KY/TN into western VA along a diffuse outflow/front. This area will lie along the southern fringe of the westerlies aloft, but thermodynamic profiles will favor occasional downbursts with wind damage. ....MO to western KY through this evening... An MCS and associated MCV are ongoing over northwest MO, with a history of measured severe outflow gusts the past few hours. Given the organized nature of the MCS/cold pool and surface heating/destabilization ongoing along an outflow-reinforced front from northern MO to southern IL/western KY, the MCS may persist into the afternoon. Damaging winds will continue to be the main concern with these storms. ....Central/northern High Plains through tonight... Subtle perturbations will continue to move around the northern periphery of the midlevel high centered over the Four Corners, with post-frontal/upslope low-level flow established from northeast CO to MT. The lower Plains should generally remained capped, with storm initiation focused by terrain circulations later this afternoon/evening from the CO Front Range into southeast WY. Isolated severe outflow gusts and large hail will be the main threats given moderate buoyancy, steep midlevel lapse rates and effective bulk shear in the 30-40 kt range. A cluster or two of storms could persist into tonight with isolated severe potential into NE. Farther north, the details of storm development/coverage are uncertain through tonight. Diurnal, surface-based convection is in question given the somewhat cool boundary layer and clouds into western ND. The potential for elevated storms, including a couple of supercells, is a bit higher tonight, with an attendant threat for isolated large hail. $$ = = = 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) .