SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

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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