SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0700 AM CST Tue Feb 23 2021 Valid 231300Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few thunderstorms will be possible across the Pacific Northwest and northern Rockies this afternoon and evening. ...Synopsis/Discussion... Broad cyclonic flow aloft will prevail across the northwest U.S. through the period, with an embedded mid-level impulse expected to pivot around the cyclonic flow and traverse the Pacific Northwest during the late afternoon and evening hours. While temperatures are expected to be sub-freezing through the troposphere at locations in higher elevations, lower terrain areas may experience above freezing temperatures at the low levels, allowing for enough charge separation to support at least a few lightning flashes across parts of the Pacific Northwest. In addition, a mid-level trough will be ejecting into the Atlantic while a southward-sagging surface cold front moves across the southern Florida Peninsula, with cooler and drier air ushering in from behind. The surface cold front is expected to undergo frontolysis across the Peninsula, with weakening low-level convergence and a lack of greater buoyancy in the -10 to -30C charge-separation layer contributing to negligible thunderstorm chances. The idea of limited lightning potential is further substantiated by the 12Z observed sounding from Miami which sampled weak mid-level lapse rates and limited overall buoyancy. ..Guyer.. 02/23/2021
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