Subj : DAY1SVR: Marginal Risk To : All From : Mike Powell Date : Fri Sep 01 2023 13:33:00 ACUS01 KWNS 011618 SWODY1 SPC AC 011616 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1116 AM CDT Fri Sep 01 2023 Valid 011630Z - 021200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN AZ AND SOUTHEASTERN CA INTO SOUTHEAST ID... ....SUMMARY... Isolated severe gusts and hail will be possible today into this evening, from southern Arizona and southeastern California to southern Idaho. ....AZ/Southeastern CA into Eastern Great Basin... Morning satellite and radar imagery shows showers and isolated thunderstorms from southern NV into western UT, within a band of clouds arcing from western AZ through eastern NV/western UT and into WY. This band and associated showers are expected to gradually shift eastward/northeastward throughout the day. Additional thunderstorm development is anticipated later this afternoon to the west of this band, where the airmass is expected to destabilize amid daytime heating and ample low/mid-level moisture. Ascent for this thunderstorm development will be provide by broad low-level convergence between the upper low drifting southwestward towards northern CA and the persistent upper ridging over the central/southern Plains. Moderate mid-level flow will exist between these two features, supporting enough vertical shear for some briefly organized storm structures, and any stronger/more persistent updrafts could produce isolated hail. Cloud bases are not expected to be high by western CONUS standards, but steep low-level lapse rates could still support strong downbursts in areas where clouds clear and some heating is realized. ....Elsewhere... Scattered to numerous thunderstorms are expected across the Southeast, where ample low-level moisture and strong heating will destabilize the airmass in the vicinity of an easterly wave moving across the region. Weak vertical shear will limit storm organization and severity, with an outflow-dominant, multicell mode anticipated. Even so, a damaging gust or two is possible amid strong water loading and forward-propagating storm structures. Ongoing cluster of showers and thunderstorms across SD may persist for the next hour or two, before dissipating as it the low-level jet weakens and the cluster continues northeastward. A few elevated thunderstorms are also possible early tomorrow morning across the Upper Midwest, forced by a strong low-level jet and related warm-air advection (and perhaps weak ascent attendant to a convectively augmented shortwave trough). ...Mosier/Weinman.. 09/01/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .