Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 09 2023 17:31:55 ACUS02 KWNS 091731 SWODY2 SPC AC 091730 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Sep 09 2023 Valid 101200Z - 111200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON AND EVENING ACROSS PARTS OF SOUTHEASTERN COLORADO...WESTERN KANSAS...NORTHEASTERN NEW MEXICO AND THE TEXAS AND OKLAHOMA PANHANDLES... ....SUMMARY... Scattered strong thunderstorms are possible across parts of the southern Rockies and adjacent Great Plains Sunday afternoon and evening. Some of these may pose a risk for severe wind and hail. ....Synopsis... Models indicate that the westerlies in the northern mid-latitudes of the eastern Pacific and North America will remain amplified through this period, with one significant trough pivoting inland across the British Columbia and Pacific Northwest coast. Downstream, mid-level ridging will remain strong across the Canadian Prairies and northern U.S. Rockies, while troughing digs across northwestern Ontario southwestward through much of the northern U.S. Great Plains and upper Mississippi Valley by late Sunday night. In the southern mid- and subtropic latitudes, flow is forecast to become less amplified, as a persistent prominent mid-level high substantively weakens to the west-southwest of the Texas Big Bend vicinity. It appears that a weak downstream low will become increasingly sheared and accelerate within confluent flow east-northeast of the southern Appalachians. This may be accompanied by the development of a weak wave along a weak surface frontal zone, across and offshore of the southern Mid Atlantic coast Sunday through Sunday night. On the northeastern periphery of the weakening subtropical high, models indicate that mid-level flow will transition from broadly anticyclonic to cyclonic across the Colorado Rockies into central Great Plains, to the south of the digging troughing across the northern Great Plains. This is forecast to be accompanied by modestly deepening surface troughing to the lee of the southern Rockies during the day Sunday, in advance of cool surface ridging nosing southward to the lee of the northern Rockies. ....Southern Rockies and adjacent Great Plains... Within the deepening lee surface troughing, models indicate that at least modest boundary-layer CAPE may develop with daytime heating, beneath steep lower/mid-tropospheric lapse rates. The NAM appears on the more aggressive side with peak mixed-layer CAPE exceeding 2500 J/kg, but general magnitudes on the order of 1000-2000 J/kg appear probable, beneath a modest (but increasingly favorably sheared) west to northwesterly mid-level flow regime. With the onset of mid-level height falls, possibly aided by an embedded short wave perturbation, scattered vigorous thunderstorms are expected to develop across and to the lee of the southern Rockies late Sunday afternoon and evening. Given the thermodynamic profiles, including the steep lapse rates and a considerable degree of unsaturation in lower/mid-levels, some of this activity may gradually organize and pose a risk for marginally severe wind and hail before weakening Sunday evening. ....Southern Mid Atlantic Coast vicinity... Strong thunderstorm development might become possible near and in advance of the developing frontal wave, particularly across parts of southeastern Virginia/eastern North Carolina late Sunday afternoon and evening. Despite generally weak lower/mid-tropospheric lapse rates, it appears that boundary-layer moisture might be sufficient to support moderate to large mixed-layer CAPE. However, due to lingering uncertainties, including the likely continuing presence of generally weak wind fields and shear, it remains unclear if the severe weather threat will meet or exceed 5 percent severe probabilities. ...Kerr.. 09/09/2023 $$ = = = 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) .