Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue May 16 2023 17:19:38 ACUS02 KWNS 161719 SWODY2 SPC AC 161718 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1218 PM CDT Tue May 16 2023 Valid 171200Z - 181200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING ACROSS PARTS OF THE SOUTHEAST AND HIGH PLAINS... ....SUMMARY... Scattered thunderstorm clusters may develop across parts of the Southeast Wednesday afternoon, and from the Rockies into the adjacent Great Plains by Wednesday evening. A few of these may be accompanied by strong to locally severe wind gusts. ....Synopsis... Mid/upper flow across the northern mid-latitudes of the Pacific into Atlantic remains amplified, with a number of embedded highs and lows in various states of evolution. The center of one mid-level high may slowly shift from the British Columbia coast vicinity into northern British Columbia, as one perturbation progresses around its eastern through southern periphery, across the Canadian Rockies by late Wednesday night. Downstream, a deeper mid-level low is forecast to dig south of the eastern Canadian Prairies into the central Canadian/U.S. Border area, while an even more prominent low and associated mid-level troughing pivot offshore of the northern Atlantic coast, and across the Canadian Maritimes. In the wake of the lead perturbation, a broadly confluent mid-level regime will slowly begin to shift east of the Atlantic Seaboard, with weak low-amplitude troughing shifting east of the middle Mississippi Valley and across the central Gulf of Mexico. In lower levels, models indicate that the center of seasonably cold surface ridging will build southeast of the upper Great Lakes into the Mid Atlantic by 12Z Thursday, with the cold front on the leading edge of this air mass advancing southward and southwestward through the Carolinas, Tennessee and middle Mississippi Valleys. Ahead of the front, seasonably warm and moist air will generally be maintained across parts of the eastern Gulf/south Atlantic Coast states through at least much of this period. Another fairly significant cold intrusion is forecast to accompany the trailing mid-level perturbation, across and to the lee of the northern U.S. Rockies. Although boundary-layer moisture preceding the associated cold front appears likely to remain seasonably modest, stronger surface heating and deep boundary-layer mixing within a corridor across the higher plains probably will become a focus for destabilization and thunderstorm development. ....Southeast... Beneath broadly cyclonic westerly mid-level flow, boundary-layer moisture (characterized by mid 60s to around 70F surface dew points) may support mixed-layer CAPE on the order of 1000-2000 J/kg in a corridor roughly centered from central Mississippi into southern South Carolina by late Wednesday afternoon. It appears that this environment will become supportive of fairly widespread thunderstorm development from mid afternoon into early evening. Despite ambient westerly deep-layer mean wind speeds near or below 20 kt, this may be sufficient to contribute to localized damaging wind gusts, aided by modestly steep low-level lapse rates and precipitation loading. ....Rockies into adjacent Great Plains... Much of the region will remain south of the influence of the primary digging low, but forcing for ascent downstream of weak northern (across the Great Basin) and southern (near Baja California) branch troughing may provide support for scattered thunderstorm development across and east of the Rockies. Beneath generally weak west-northwesterly deep-layer mean flow, this activity will tend to advect off the higher terrain through Wednesday evening. As convection spreads into the Great Plains, the warm and deeply mixed boundary-layer may possess sufficient moisture and CAPE to support upscale growing clusters with increasing potential to produce strong wind gusts, before boundary-layer instability wanes later Wednesday evening. ...Kerr.. 05/16/2023 $$ = = = 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) .