SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1216 AM CDT Sun Oct 25 2020 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. Sunday through Sunday night. ...FL to the Carolina/Virginia Coastal Vicinity... An upper shortwave trough will be advancing northeastward early in the period while a cold front drops southward to the lee of the Appalachians across the Piedmont. Meanwhile, the southern extent of the front across FL will become increasingly diffuse over the Peninsula. Moist southerly low-level flow ahead of these features amid weak instability and modest forcing for ascent should result in isolated thunderstorms through the afternoon. ...Four Corners into the Southern Great Plains Vicinity... A series of shortwave troughs will dig southward across the western U.S. and across the northern Plains on Sunday, bringing a belt of strong southwesterly mid/upper level flow from the southwestern U.S. northeastward across the Plains. As an intense surface high builds over the northern Rockies and adjacent High Plains, a strong cold front will surge southward across the central and southern Plains. A somewhat shallow intrusion of seasonably cold air will surge southward behind the front, while southerly low/mid level flow maintains moist advection aloft. Isolated elevated thunderstorm activity appears likely during the evening and overnight in this warm advection regime, atop the shallow cold layer in the vicinity of the midlevel baroclinic zone, from parts of western TX through OK and into parts of the Ozarks. Further west across the Great Basin, forcing for ascent will increase over the Four Corners vicinity as the upper trough digs southward across the western Great Basin. As this occurs, cooling aloft will result in steepening lapse rates amid modest midlevel moisture. This should result in weak, but adequate instability for isolated thunderstorm development Sunday afternoon and evening across the Four Corners vicinity. ..Leitman.. 10/25/2020
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