Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 12 2023 05:47:38 ACUS01 KWNS 120547 SWODY1 SPC AC 120546 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1246 AM CDT Sat Aug 12 2023 Valid 121200Z - 131200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN OHIO ACROSS PENNSYLVANIA AND INTO PARTS OF CENTRAL NEW YORK... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OHIO VALLEY INTO SOUTHWEST NEW ENGLAND...OVER PARTS OF THE CENTRAL PLAINS...AND OVER THE TENNESSEE VALLEY... ....SUMMARY... Severe thunderstorms are likely across portions of the Ohio Valley and Northeast, parts of the central Plains region, and across the Tennessee Valley today. The most concentrated area of damaging storms appears to extend from northeast Ohio across parts of Pennsylvania and into central New York, where damaging hail, wind, and tornado or two will be possible. ....Synopsis... An upper ridge will be located over the southern Plains and lower MS Valley today, with moderate mid and high-level winds from the northern Rockies and Plains across the Great Lakes and into the Northeast. Embedded in this broad region of primarily cyclonic flow aloft, a shortwave trough will move from the upper Great Lakes eastward across OH, PA, NY by 00Z, with 500 mb speeds of 40-50 kt. At the surface, low pressure will move east across parts of southwest Ontario and toward northern NY by 00Z. Winds around 850 mb will increase out of the southwest, aiding the advection of an unstable air mass across OH, PA, and NY. Low-level shear will be maximized near the nose of the low-level jet and theta-e advection plume from northeast PA into parts of central NY. Deep-layer shear will overlap an unstable air mass extending westward into OH. Elsewhere, hot conditions will again prevail over the southern Plains, with a low developing across northwest TX/eastern Panhandle. North of the low, a boundary will stretch from northeast NM eastward across northern OK, with easterly winds over KS and southeast OK maintaining a moist and unstable air mass. Farther north, a weak trough will develop over western SD and NE, beneath moderate west/northwest flow aloft favoring hail. ....OH into southern New England... As the shortwave trough approaches the area, southwest low-level flow will help spread moisture northeastward ahead of a cold front, with 1500-2000 J/kg MUCAPE widespread by midday/late afternoon. Initial development is likely along the southern shore of Lake Erie and extending east/northeast across northwest PA and southwest NY just south of the stable lake shadow. Other storms are likely to develop around 19Z as well over northeast PA and across much of central NY as the air mass will be uncapped. Forecast soundings from several models all show shear and instability favorable for supercells, especially near the nose of the low-level heat plume. Effective SRH over 200 m2/s2 is forecast, with 0-1 values of 100-150 m2/s2 which will support a tornado threat. Elongated hodographs in the mid to upper levels along with the cool air aloft will strongly favor damaging hail with the strongest cells. A few hail reports approaching 2.00" diameter will be possible through early evening, given supercell wind profiles and cool air aloft. ....TX Panhandle across western and northern OK and southern KS... Hot temperatures will easily uncap the air mass this afternoon, just south and west of a moist plume extending out of central OK and across the OK/northern TX Panhandles. Indications are that the moist upslope will yield activity forming near Pueblo CO, with hail and wind potential as it moves east along the instability axis. Storms will likely initiate over the TX Panhandle as well, and models indicate substantial outflow may be produced with forward propagation across northwest OK and into southern KS. Hail may also occur during the peak heating hours, given expected strong updrafts and as storms encounter the moist plume. ....Mid MS/Lower OH Valley southeastward across AL... A very moist and unstable air mass will again exist today with mid 70s F dewpoints and strong heating. Midlevel temperatures will also be relatively cool, resulting in MLCAPE in the 3000-4000 J/kg range. This will conditionally favor damaging downbursts with storms that develop in the uncapped air mass. Further, models indicate that a remnant outflow, or perhaps rejuvenated MCS, may move across Middle TN into northern and eastern AL, which would enhance damaging-wind potential. As such, as Slight Risk has been introduced. ....Western SD into northern NE... Developing southeast surface winds will help bring mid to upper 50s dewpoints northwestward toward the Black Hills. Strong heating will result in steep lapse rates, and this along with elongated hodographs will conditionally favor storms producing hail, despite MUCAPE generally less than 1000 J/kg. Deeply mixed low levels will also favor evaporative cooling and downdraft potential, as storms form over the higher terrain after 21Z and move southeastward during the evening. ...Jewell/Lyons.. 08/12/2023 $$ = = = 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) .