Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon May 01 2023 05:28:12 ACUS01 KWNS 010528 SWODY1 SPC AC 010526 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1226 AM CDT Mon May 01 2023 Valid 011200Z - 021200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF NORTHWESTERN NEVADA INTO SOUTHEASTERN AND CENTRAL OREGON... ....SUMMARY... Strong thunderstorms may impact parts of northwestern Nevada into southeastern and central Oregon late this afternoon and evening, accompanied by at least some risk for severe wind gusts. ....Synopsis... A blocking mid/upper high persists over the Newfoundland and Labrador vicinity. However, a pair of flanking lows to its southeast and, particularly, southwest have become much more prominent. The western low is now centered over the Great Lakes, but cyclonic flow encompasses much of the U.S. to the east of the Rockies. This low may reform a bit farther to the east (from Lower Michigan into the lower Great Lakes) today through tonight, in response to a significant mid-level perturbation pivoting around its eastern through northern periphery. At the same time, a deep, occluding surface cyclone will gradually become centered beneath it, with the trailing cold front advancing away from much of the Atlantic Seaboard, while slowing and/or stalling across the Florida Peninsula and northern Gulf of Mexico into the Texas South Plains. In the wake of a preceding cold front (as far south as the Bahamas, Caribbean and southwestern Gulf of Mexico at the outset of the period), only a gradual boundary-layer modification may commence across the Florida Peninsula, northern and western Gulf, and southern Texas. Dry and/or stable conditions will generally prevail across most areas east of the Rockies, with negligible risk for thunderstorms, aside from perhaps areas to the east of the lower Great Lakes, beneath the mid-level cold core. Meanwhile, across the eastern Pacific into western North America, models indicate that another low will continue to evolve within elongated mid/upper troughing near the Pacific coast, and become cut off from the westerlies while digging near/offshore of the coast toward the San Francisco Bay vicinity by 12Z Tuesday. A cold front already advancing inland of much of the Pacific coast is forecast to advance across the Sierra Nevada, and southward near/to the west of Baja California, to the south of slowly deepening low pressure over the interior Northwest. However, due to the lack of a substantive return flow of moisture from the subtropical Pacific, it appears that moisture content across much of the West will remain relatively low. Some thunderstorm activity might develop this afternoon and evening across parts the Great Basin and northern Intermountain region, into the Rockies, and perhaps near central California coastal areas by late tonight, but this probably will remain rather sparse in coverage. ....Northern Great Basin/Intermountain region... A relative concentration of thunderstorm activity may become focused near/ahead of the cold front trailing the surface low, across parts of northwestern Nevada into southeastern Oregon late this afternoon into evening. It appears that this could be aided by mid-level forcing for ascent downstream of a short wave perturbation pivoting around the developing coastal mid/upper low. Despite the limited boundary-layer moisture, it appears that steepening lapse rates supported by differential thermal advection, daytime heating and deep mixing will yield sufficient CAPE for thunderstorm initiation. Initially scattered, this activity may congeal into a north-northwestward propagating cluster into early evening, in the presence of strong deep-layer shear, with downward mixing of stronger flow from aloft (30-50+ kt flow in the 700-500 mb layer) in consolidating downdrafts contributing to the risk for at least locally severe gusts. ...Kerr/Moore.. 05/01/2023 $$ = = = 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) .