SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 PM CDT Wed Sep 23 2020 Valid 240100Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ISOLATED STRONG STORMS MAY POSE SOME RISK FOR SEVERE WEATHER TONIGHT ACROSS PARTS OF CENTRAL AND SOUTHERN MISSISSIPPI...PORTIONS OF THE UPPER MIDWEST...AND WEST OF THE WASHINGTON CASCADES... ...SUMMARY... Thunderstorm activity which could pose at least some risk for a tornado may persist tonight across parts of central and southern Mississippi. ...01Z Outlook Update... ...Lower Mississippi Valley... Thunderstorm activity has generally been confined to a short narrow band, just in advance of the center of Beta, apparently aided by a weak mid-level thermal trough (as suggested by the Rapid Refresh near/just above 700 mb). As the surface low center of Beta migrates across the Mississippi River into southwest/west central Mississippi overnight, it is possible that this may continue. Supported by inflow of boundary-layer moisture characterized by lower/mid 70s F dew points, in the presence of modest clockwise curved low-level hodographs, it is possible that there could be occasional low-level mesocyclone strengthening which could pose at least some risk for a tornado. ...Elsewhere... ...Thunderstorm activity may continue to increase this evening, into the overnight hours, within a narrow corridor along a frontal zone across parts of north central Minnesota into northern Wisconsin and adjacent Upper Michigan. This may be aided by forcing associated with a short wave trough digging into the region, and its possible that thermodynamic profiles and cloud-bearing layer shear may be marginally conducive from some hail and gusty winds in stronger storms. ...Isolated thunderstorm development has also occur ahead of the digging mid-level trough across parts of the western Dakotas, where boundary-layer instability largely driven by daytime heating became locally maximized. This activity is now waning north/northeast of the Black Hills vicinity, but could perhaps continue into the 02-04Z time frame. ...As the base of a 500 mb thermal trough with temperatures near or below -20C migrates inland, scattered thunderstorm development appears increasingly possible west of the Washington Cascades by 04-06Z. It is possible that boundary-layer instability may become marginally sufficient, in the presence of moderate to strong deep-layer mean flow and shear, to support some risk for hail and gusty winds in stronger activity. ..Kerr.. 09/24/2020
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