SPC 0830Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0149 AM CST Fri Jan 22 2021

Valid 241200Z - 251200Z


Severe storms are not expected across the U.S. on Sunday.

Mean long-wave upper troughing is forecast to remain over the
western U.S. this period, as smaller-scale/short-wave troughs rotate
through the broader cyclonic flow field.  The first of these --
initially lying across southern California and northern Baja, is
expected to shift eastward across the Desert Southwest and southern
Rockies, and then reach the southern High Plains region as a
negatively tilted, deamplifying impulse late in the period. 
Meanwhile, the second short-wave feature will lie just off the
western Canada coast initially, with an associated/elongated
north-south lobe of vorticity extending from Alaska to just off the
Pacific Northwest coast.  With time, the short-wave energy will dig
southward along the West Coast, to a position just inland by the end
of the period -- thus reinforcing the pre-existing long-wave trough.

At the surface, a cold front associated with the initial short-wave
trough ejecting across the Southwest will move across New Mexico and
later Texas.  East of this system, a west-to-east baroclinic zone
will become established across the Mid Mississippi and Tennessee
Valleys through the end of the period.

With much of the CONUS remaining cool and stable through the period,
deep convective potential will be limited to the southwestern and
south-central portions of the country.  Cold air/steep lapse rates
aloft accompanying the upper system will support potential for
sporadic lightning flashes across portions of the Four Corners
states.  Later, as downstream warm advection increases across the
south-central U.S., elevated convection -- including scattered
thunderstorms -- will likely evolve during the second half of the
period.  Muted instability, however, precludes appreciable risk for
severe storms.

..Goss.. 01/22/2021

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