SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0632 AM CST Mon Dec 21 2020

Valid 211300Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...Synopsis/Discussion...
A progressive upper-air pattern will continue this period, with
ridging shifting eastward from the Great Basin/inland Pacific
Northwest, across the central/northern Rockies to the Great Plains. 
A well-defined trough -- initially located from southern WV across
GA to the northeastern Gulf -- will eject offshore from the Atlantic
Coast, while a stronger perturbation now over the upper Mississippi
Valley region amplifies and digs southeastward.  A broad area of
cyclonic flow around a synoptic-scale trough should result over the
coastal Mid-Atlantic and New England by the end of the period.

At the surface, a cold front -- initially drawn from the Atlantic
across central/southwestern FL Peninsula to the eastern Gulf -- will
proceed southeastward past the peninsula by 00Z.  Isolated thunder
may occur the next few hours in the prefrontal belt of precip and
embedded convection, before the regime weakens amidst lessening
low-level convergence, and shifts southeastward out of the area. 
Weakening deep shear and modest lapse rates/buoyancy should preclude
a severe threat.  Elsewhere over the CONUS, the air mass will be to
dry and/or stable for thunderstorms.

..Edwards.. 12/21/2020

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