SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1045 PM CST Mon Nov 02 2020 Valid 031200Z - 041200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Aside from southern portions of the Great Basin into parts of the Colorado Plateau, the risk for thunderstorms appears negligible across much of the U.S. today through tonight. ...Discussion... Models indicate that the stronger westerlies will trend more zonal and increasingly confined to the northern mid-latitudes during this period. This is forecast to include the deamplication of large-scale mid/upper troughing, now east of the Atlantic Seaboard, across the Canadian Maritimes and adjacent northwestern Atlantic, leaving broadening anticyclonic flow in its wake, across the British Columbia coast through the St. Lawrence Valley. As this occurs, in lower levels, the center of fairly expansive cold surface ridging appears likely to shift from the central Gulf Coast states into areas off the north Atlantic coast, but a trailing ridge axis (and associated potentially cold/dry air) is expected to be maintained west-southwestward across much of the Gulf Coast region. This will continue to inhibit return flow off the Gulf of Mexico, where boundary-layer moistening will only very slowly be underway, in the wake of the recent cold intrusion. A narrow plume of elevated moisture return, emanating from the lower-latitude eastern Pacific, will still be ongoing early this morning across the lower Colorado Valley into the southern Great Basin, ahead of the increasingly deformed remnants of a broad, weak mid-level low slowly progressing across the southern Sierra Nevada. It appears that the continuing approach of more progressive upstream short waves will force the eastward acceleration of this perturbation, and contribute to further suppression of a downstream ridge emanating from the Mexican Plateau. As this occurs, veering lower/mid tropospheric flow across the Southwest will gradually begin to cut off the moisture return. However, there may still be sufficient destabilization to support a continuing risk for scattered weak thunderstorm activity across parts of the southern Great Basin into the Colorado Plateau through late this afternoon. ..Kerr.. 11/03/2020
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