SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1042 PM CST Sun Nov 01 2020

Valid 021200Z - 031200Z


Aside from portions of the lower Colorado Valley vicinity into the
southern Great Basin, the risk for thunderstorms appears negligible
across much of the U.S. today through tonight.

Models indicate that broad and amplified large-scale ridging will
persist within the westerlies, across the Pacific coast through the
Canadian Prairies/U.S. Great Plains and Mississippi Valley through
this period, with similar amplitude troughing downstream, across the
Atlantic Seaboard into the western Atlantic.

A surface cold front associated with the mid/upper troughing is
expected to be in the process of advancing south of the Florida
Peninsula by early today.  Considerable low-level cooling and/or
drying will continue to spread southward in its wake, through much
of the Gulf of Mexico and well into the western Atlantic.

Within the larger-scale ridge, it does appear that the highest
mid-level heights (emanating from the subtropical latitudes) will
begin to become suppressed across the Intermountain West and
Rockies.  This is expected to occur as weak smaller-scale troughing,
and an embedded cyclonic circulation, are forced inland of the
southern California coast, in response to the approach of a
splitting short wave trough across the southern mid-latitude and
subtropical eastern Pacific. 

The lead perturbation is forecast to progress into parts of the
southern Great Basin and Plateau region by late tonight, preceded by
an elevated return flow of moisture emanating from the Gulf of
California and lower latitude eastern Pacific.

...Lower Colorado Valley into southern Great Basin...
Models suggest that the most substantive moisture return will be
near or above the 700 mb level.  However, in the presence of
modestly steep mid-level lapse rates, it appears that increasing
convective and conditional instability will become supportive of
occasional, scattered weak thunderstorm activity throughout the
period, aided by large-scale forcing for ascent associated with the
inland migrating perturbation.

...South Florida and Florida Keys...
A low risk for thunderstorm activity may linger near/just southeast
of the Keys and southeast Florida coastal areas into the beginning
of this forecast period.  However, this risk is expected to become
increasingly negligible shortly thereafter, with the southward
progression of the cold front.

..Kerr.. 11/02/2020

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