SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 PM CST Wed Feb 10 2021 Valid 111200Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF THE GEORGIA INTO SOUTH CAROLINA PIEDMONT... ...SUMMARY... A couple of strong thunderstorms may impact parts of the Georgia into South Carolina Piedmont late this afternoon and evening, accompanied by at least some risk for severe weather. ...Synopsis... Models indicate that lowest mid-level heights will gradually consolidate near/north of the North Dakota/Minnesota international border area during this period. Beneath broadly confluent flow to the south of this feature, across and to the lee of the Rockies, it appears that cold high pressure, characterized by Arctic air, will become increasingly entrenched across much of the Great Plains and Mississippi Valley. By late tonight into early Friday, cold high pressure is also forecast to build southward to the lee of the southern Appalachians. At the same time, mid-level subtropical ridging likely will maintain an influence across much of the eastern Gulf of Mexico and Southeast. However, it appears that the high center near the Bahamas is weakening, and a series of short wave perturbations, emanating from larger-scale troughing now digging across parts of the Southwest and Baja, may contribute to suppression of mid-level heights across the Tennessee Valley/southern Appalachians vicinity. The large-scale trough is forecast to continue digging into the Mexican Plateau into early Friday, as a vigorous upstream perturbation (emanating from the mid-latitude Pacific) digs inland across the California coast. Around the northern periphery of the subtropical ridge, and ahead of the lead upstream troughing, a moistening southerly return flow is expected to continue off the Gulf of Mexico into much of the Gulf and south Atlantic Coast states. Across much of Texas into the lower Mississippi/Tennessee Valleys and southern Mid Atlantic region, this will generally be maintained above the slowly southward advancing, shallow leading edge of the Arctic air mass. However, aided by forcing for ascent associated with the short wave perturbations, destabilization aloft is expected to be sufficient for scattered areas of generally weak thunderstorm activity. ...Georgia/South Carolina Piedmont... Models do suggest that one short wave perturbation may be accompanied by weak surface frontal wave development across central Alabama into the Georgia Piedmont by this afternoon, where warm sector boundary-layer warming and dew points in the lower 60s may contribute to CAPE on the order of 500 J/kg. Guidance suggests that this may coincide with strengthening southwesterly to westerly lower/mid tropospheric flow near the front, ahead of the frontal wave, including speeds on the order of 30-50 kt in the 850-500 mb layer. It appears that this environment could become at least marginally conducive to vigorous thunderstorms with occasional supercell structures. These may be accompanied by the risk for small to marginally severe hail and potentially damaging wind gusts, and spread into the South Carolina Piedmont before diminishing this evening. ..Kerr.. 02/11/2021
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