SPC AC 171725
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1225 PM CDT Fri Sep 17 2021
Valid 181200Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for organized severe storms is expected to remain low
across the U.S. mainland on Saturday.
...Great Basin area...
A shortwave trough now situated off the southern California coast
will accelerate northeast into the Great Basin Saturday in response
to increasing southwesterly winds aloft associated with an upper
trough that will amplify across the Pacific Northwest. Scattered
showers and thunderstorms will likely be ongoing early Saturday
within plume of subtropical moisture along the warm conveyor belt
from western AZ to eastern NV and western UT. Activity will spread
east through AZ and UT through the morning and into the afternoon.
It currently appears that widespread multi-layer clouds and areas of
precipitation will limit destabilization potential, especially over
much of UT and northern AZ where vertical shear profiles will be
more supportive of organized storms. Will therefore maintain less
than 5% severe probabilities for this update. However, should it
become apparent that instability will be greater than currently
anticipated, a categorical upgrade may be needed in day 1 outlooks.
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z