SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0631 AM CST Fri Nov 06 2020 Valid 061300Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the U.S. mainland. ...Synopsis/Discussion... In mid/upper levels, a reasonably high-amplitude synoptic pattern will prevail over the CONUS. From west-east: a strong trough is initially evident in moisture-channel imagery offshore from the Pacific Northwest and northwestern CA, with an embedded 500-mb low west of the OR coast. The associated cyclone is forecast to dig south-southeastward approximately along the northern CA coast through the period, crossing the SFO Bay Area overnight before pivoting inland toward the Central Valley. Strong height falls and cooling aloft are expected over the suitably moist coastal/offshore marine layer ahead of the low. Associated mostly shallow convection may deepen enough on an isolated basis to produce near-shore lightning. Elsewhere, synoptic ridging prevails from northern MX to the Corn Belt. To its south and southeast, a broad, weak, cut-off, mid/upper cyclone is located over much of AR, east TX, LA, the Delta region, and the northwestern Gulf, with the circulation currently centered near Toledo Bend Reservoir. Through 12Z tomorrow, this feature is progged to meander erratically and slowly near its present position, orbited by mesoscale vorticity lobes, while gradually broadening and weakening. Associated negatively tilted 500-mb troughing may start to link with the height weakness accompanying what now is T.D. Eta over the northwestern Caribbean, near the end of this period, or on day-2. Divergence aloft over a moist and minimally inhibited Gulf air mass may support isolated thunderstorms from the Gulf reaching parts of the coast near southeastern LA. Isolated thunderstorms over the relatively high-theta-e air of the Gulf Stream also may reach portions of the Atlantic coast from the Carolinas southward, and across south Florida. ..Edwards/Kerr.. 11/06/2020
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