SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1120 PM CST Thu Jan 28 2021

Valid 291200Z - 301200Z


The risk for severe thunderstorm appears negligible across the U.S.
today and tonight.


The upper trough near the Pacific coast this morning will intensify
and develop eastward toward the southwestern U.S. through the first
half of the period, becoming oriented over the southern/central High
Plains by Saturday morning. Isolated thunderstorms may be ongoing
across parts of southern California at the beginning of the period,
near the exit region of an intense mid/upper jet streak at the base
of the trough. Cold temperatures aloft will support steep lapse
rates, resulting in a few hundred J/kg MUCAPE. These conditions will
spread eastward across the lower Colorado Valley and lower desserts
of southern AZ during the afternoon and evening and isolated
thunderstorms may continue as midlevel moistening allows for
continued weak instability.

Further east, height falls ahead of the upper trough will result in
surface cyclogenesis over the central/southern Plains late in the
period. Southerly low level return flow will bring modest increases
in near-surface moisture across parts of the southern Plains.
However, this moisture will remain shallow and a midlevel warm/dry
layer will persist between 850-650 mb. This will prevent
surface-based convection from developing, but forecast soundings
show steep midlevel lapse rates and a deep, saturated layer above
650mb. As stronger ascent shifts eastward into the Plains toward the
end of the period, isolated elevated thunderstorms are possible.

..Leitman.. 01/29/2021

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