SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0238 PM CDT Mon Jul 31 2023 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS...LOWER/MID MISSISSIPPI VALLEY...COASTAL SOUTHEAST...AND ARIZONA... ...SUMMARY... Isolated severe thunderstorms remain possible over portions of the northern/central Plains, coastal Southeast, lower Missouri Valley to west-central Gulf Coast, and Arizona. ...20Z Update... No changes have been made to the prior outlook. ..Gleason.. 07/31/2023 .PREV DISCUSSION... /ISSUED 1121 AM CDT Mon Jul 31 2023/ ...MO to LA this afternoon into tonight... Multiple thunderstorm clusters occurred overnight, and the remnants of convection with outflow and debris clouds persist from southern AR into LA, and across northwest MO. The relatively widespread convective overturning/modification suggests the environment will not have sufficient time to recover by this afternoon. There will be some potential for additional development along the outflow boundary moving southward into southern LA this afternoon, where isolated downbursts may occur. Otherwise, the more probable scenario is for slightly elevated storms to form again tonight in the strengthening warm advection zone across MO. Lapse rates will not be as steep as prior days and midlevel temperatures will be relatively warm in proximity to the southern Plains ridge, so any hail/wind threat should remain marginal. ...Dakotas to northeast CO this afternoon into tonight... Lingering low-level moisture in a weak upslope flow regime will support scattered thunderstorm development this afternoon/evening from the Front Range in northeast CO northward into eastern WY. Midlevel lapse rates will not be as steep as prior days as a result of the monsoonal moisture plume spreading northeastward across UT/CO/WY, and flow aloft will also be relatively weak. Thus, primarily multicell clusters with isolated strong-severe outflow gusts will be the main threat as convection spreads eastward toward western NE and vicinity by tonight. Farther north into ND, the focus for storm development will be nebulous at best. There will be a small chance for diurnal storms in the differential heating zone across far southwest ND by late afternoon, and a storm or two could approach the international border from SK tonight. However, confidence in either scenario is low. ...Fl to Carolinas this afternoon/evening... A weak midlevel trough over the southeast Atlantic states and daytime heating in cloud breaks will drive diurnal convection this afternoon. The primary wind shift/front extends across north FL and off the coasts of the Carolinas, leaving terrain influences and a weak outflow boundary to focus thunderstorm development this afternoon. Lapse rates aloft are poor and buoyancy will be rather modest by summer standards - both of which suggest today is a low-end downburst day (at best) into the Carolinas. Stronger surface heating and destabilization will occur farther south into FL, where a few pulse severe storms with downburst winds will be possible this afternoon. ...AZ this afternoon/evening... With prior convection and the approach of a weak wave from northwest Mexico, there's been an increase in low-level moisture and a decrease in low-midlevel lapse rates since yesterday across southern AZ. Still, isolated strong outflow gusts will be possible with convection from southeast AZ northwestward in the vicinity of the Mogollon Rim, which is where the weaker convective inhibition is expected this afternoon/evening.
