SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1050 AM CST Wed Nov 18 2020

Valid 191200Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Aside from portions of the Pacific Northwest coast vicinity, the
risk for thunderstorms appears negligible across much of the U.S.
Thursday through Thursday night.

...Synopsis...
Models indicate that the westerlies will trend less amplified across
the Pacific coast through the Atlantic Seaboard during this period. 
Persistent large-scale mid-level troughing near the British
Columbia/Pacific Northwest coast is forecast to break down, with
perhaps the most significant remnant perturbation accelerating east
of the northern Rockies through northwestern Ontario and the upper
Great Lakes region by 12Z Friday.  Downstream large-scale troughing
appears likely to gradually recede to higher latitudes while
continuing to shift away from the Atlantic coast.

In lower levels, however, the southwestern flank of cold surface
ridging has maintained a considerable influence across much of the
Gulf of Mexico and Gulf Coast/Southeast vicinity.  Models suggest
that boundary-layer recovery over the Gulf of Mexico, and the
development of a southerly inland return flow, will continue to be
hampered by lingering surface ridging through this period. 
Particularly east of the Rockies, this will continue to contribute
to generally dry and/or stable conditions with negligible risk for
thunderstorms.

...Pacific Northwest...
Models continue to indicate that mid-level height rises will be
underway, and the mid-level thermal trough axis (-32 to -34 C at 500
mb) may be in the process of shifting east of the Cascades by 12Z
Thursday.  However, guidance indicates that the western edge of the
cold core (AOB -30C at 500 mb) will linger west of the Cascades into
at least Thursday afternoon, while deep-layer flow also remains at
least broadly cyclonic.  Perhaps aided by large-scale ascent
associated with a weak embedded, inland migrating perturbation,
modest westerly low-level onshore/upslope flow, and destabilization
associated with insolation, a few weak thunderstorms appear possible
to the west of the Cascades Thursday.

..Kerr.. 11/18/2020

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