Subj : DAY2SVR: Nws Storm Predic To : All From : Mike Powell Date : Sun Aug 20 2023 14:56:00 ACUS02 KWNS 201720 SWODY2 SPC AC 201719 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Sun Aug 20 2023 Valid 211200Z - 221200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS ARIZONA INTO THE EASTERN GREAT BASIN...AND ACROSS PARTS OF THE UPPER MIDWEST... ....SUMMARY... Widely scattered strong thunderstorms may impact parts of Arizona into the eastern Great Basin vicinity through Monday evening, posing a risk for strong gusts and hail. Additional strong storms with a risk of hail are possible across parts of the Upper Midwest Monday evening/ovenright. ....Synopsis... A strong upper anticyclone will be centered over the Lower MO Valley on Monday. Much of the U.S. from the Rockies to the Southeast and Mid-Atlantic coasts will remain under the influence of the strong upper ridge. A belt of stronger mid/upper level flow will exist on the western and northern periphery of the upper ridge over AZ into the Great Basin, arcing north/east across MT to the upper Great Lakes. A very moist airmass will reside beneath the upper ridge over much of the Midwest. Surface dewpoints in the upper 60s to upper 70s F are forecast from the lower/mid-MO to the Mid-MS/Lower OH Valley vicinity. A surface front will stretch from a weak low over SD eastward across central MN into WI and Lower MI. Strong instability will exist across the warm sector, but strong midlevel capping will preclude thunderstorm activity across much of the Midwest. The exception will be within the band of stronger mid/upper westerlies across the Upper Midwest/Great Lakes vicinity where elevated convection during the evening/overnight may pose a Marginal (level 1 of 5) severe risk. Additional isolated severe thunderstorms will be possible within the belt of stronger southerly mid/upper flow and abundant midlevel moisture across AZ and the eastern Great Basin vicinity. ....AZ/UT/ID/WY... A band of 30-50 kt 700-500 mb southerly flow will overspread the region in conjunction with a plume of strong midlevel moisture. At the surface, near-60 F dewpoints will overspread south-central AZ, with upper 40s to 50s F dewpoints spreading northward across UT into western WY/eastern ID. While cloudiness will limit stronger heating/destabilization, modest midlevel lapse rates combined with a rather moist thermodynamic profile for this part of the country will allow for 500-1000 J/kg MLCAPE. Effective shear magnitudes greater than 25-30 kt also will support organized convection. Strong to severe gusts will be possible. Across south-central AZ where stronger boundary-layer moisture and greater heating may occur, isolated large hail also is possible. Muted heating/weaker instability across UT/ID/WY will likely preclude higher severe potential, but a Slight risk (level 2 of 5) may be needed in future outlooks across parts of AZ if confidence increases in greater coverage of severe storms. ....Upper Midwest... Capping will likely preclude surface-based convection. However, warm advection during the evening/overnight atop the west to east oriented surface front will allow for elevated thunderstorm development. Modest midlevel lapse rates and strong MUCAPE will support isolated vigorous updrafts. Marginally severe hail will be possible with these stronger cells. ...Leitman.. 08/20/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .