SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1241 AM CDT Wed Oct 07 2020

Valid 071200Z - 081200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NEW YORK TO
NEW ENGLAND...

...SUMMARY...
Gusty winds are possible with thunderstorms later today from New
York into New England.

...NY to New England...

Strong mid-level short-wave trough is currently digging southeast
across the Great Lakes. This feature is forecast to progress into NY
early in the period before ejecting off the New England coast by
08/00z. Latest model guidance suggests 120-150m mid-level height
falls and pronounced high-level difluence will spread across the
northeastern US during daylight hours. This strongly-forced system
will encourage scattered low-topped convection along/ahead of a cold
front as it surges across NY during the late morning hours. While
boundary-layer moisture is not forecast to be that significant, and
overall moisture is somewhat meager, steep low-level lapse rates and
cooling profiles strongly favor surface-based convection, especially
along the front where convergence will be maximized. Latest CAMs
support this scenario with a band of weak elevated convection
expected to spread ahead of the front early, then isolated-scattered
convection developing ahead of the front where partial sunshine and
surface thermals will be maximized. 

Given the increasing westerly flow in the cloud-bearing layer, there
is some concern for stronger winds mixing to the surface; however,
weak buoyancy could limit this mixing. Will maintain 5 percent
severe probabilities for gusty winds primarily due to
buoyancy/updraft concerns. If it becomes more clear that robust
convection will be more concentrated then severe probabilities may
be adjusted accordingly. Severe threat should spread across New
England during the afternoon and off the Atlantic Coast by early
evening.

..Darrow/Squitieri.. 10/07/2020

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