SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 PM CST Wed Jan 20 2021 Valid 211200Z - 221200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe weather is not expected across the U.S. during the day1 period. ...Discussion... Upper low off the northern Baja Peninsula will eject east and deamplify as it approaches west TX by early evening. Currently, isolated thunderstorms continue ahead of the upper low from the northern Gulf of California into southwest AZ. Cold mid-level temperatures (-20C at 500mb) north of the associated mid-level jet will result in steep lapse-rate environment across the southern half of AZ during the first half of the period. This will aid buoyancy for potential thunderstorm development. Latest thinking is some thunder threat should linger across this region until the short wave passes during the mid afternoon. Downstream, in response to the approaching short wave, LLJ should strengthen across deep south TX then shift east across the Coastal Plain of TX. By 22/00z, low-level warm advection will focus across southeast TX into the lower MS Valley. Forecast soundings across this region suggest the most buoyant parcels will initially be rooted between 850-800mb. In the absence of meaningful boundary-layer moisture returning inland, it appears the primary thunder threat will be associated with weak, elevated convection. ..Darrow/Moore.. 01/21/2021
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