SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0146 PM CST Sat Nov 21 2020 Valid 212000Z - 221200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected today or tonight. ...20Z Update... Recent surface analysis places a low over northeast OK, with a cold front extending southwestward from this low back across the southern TX Panhandle and into southeast NM. The cold front also extends east-northeastward across northern AR and into the TN Valley. Modest warm-air advection across the western portion of this frontal zone will continue to contribute to showers and occasional thunderstorms from northern OK through the Ozark Plateau. This corridor of showers and thunderstorms will gradually shift southward as the cold front moves southward throughout the remainder of the period. ..Mosier.. 11/21/2020 .PREV DISCUSSION... /ISSUED 1017 AM CST Sat Nov 21 2020/ ...Synopsis... A series of low-amplitude shortwave troughs will move eastward from the Four Corners to the lower OH Valley, in advance of an amplifying northern stream trough over the upper-middle MO Valley. The northward return of boundary-layer dewpoints in the low-mid 60s across east TX will contribute to weak buoyancy along a frontal zone from southern OK into the Ozarks. A few elevated thunderstorms are expected later today into tonight atop the frontal surface, in association with embedded speed maxima progressing eastward from northern NM/southern CO. Other isolated thunderstorms may also occur this afternoon into tonight along the path of the embedded speed maxima, originating with weak buoyancy over the higher terrain over northern NM/southern CO and spreading eastward above the shallow cool air mass over the southern High Plains. Otherwise, continued low-level air mass modification and some cooling in the 850-700 mb layer noted from 00z to 12z at Miami may allow sufficiently deep convection for isolated lightning flashes near the southeast FL coast.
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