SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1040 AM CST Sat Jan 02 2021

Valid 031200Z - 041200Z


The risk for thunderstorms appears negligible across much of the
U.S., Sunday through Sunday night.

Within one branch of split westerlies emanating from the
mid-latitude eastern Pacific, it appears that general large-scale
mid-level troughing will undergo substantive evolution, broadening
while shifting east of the southern Great Plains through the
Atlantic Seaboard.  As it translates eastward, initially prominent
mid-level subtropical ridging centered over the Caribbean and
Bahamas will become increasingly suppressed through this period.

As a couple of short wave perturbations embedded within this regime
progress across and dig to the lee of the Rockies,  one significant
downstream impulse, emerging from the southern Great Plains, is
forecast to accelerate across the Ohio Valley through the northern
Mid Atlantic/southern New England coast vicinity Sunday through
Sunday night.  Models indicate that this will support significant
surface cyclogenesis along a frontal zone across and northeast of
the southern Mid Atlantic coast.  While the warm conveyor of this
developing system may emanate from the southern Gulf of Mexico, it
appears that it will be confined to a narrow plume across the
Florida Peninsula into areas near or just east of the southern Mid
Atlantic coast by 12Z Sunday, before continuing to spread eastward.

In the wake of this cyclone, generally dry and/or stable conditions
are expected to prevail across most areas east of the Rockies, and
into the Intermountain West.  A plume of moist air emanating from
the subtropical Pacific does appear likely to overspread the Pacific
coast (from central California northward), ahead of a cold front
trailing a deep, occluding cyclone migrating toward the British
Columbia coast.  However, relatively warm mid level air on the
western flank of building mid-level ridging shifting inland of the
Pacific coast is expected to preclude an appreciable risk for
thunderstorms through at least this period.

Showers are possible Sunday within the narrow plume of moisture
overspreading the Florida Peninsula.  However, it appears that this
will be mostly elevated above a stable boundary-layer, with
relatively warm layers aloft suppressing potential for

By 12Z Sunday, model output generally suggests that the primary risk
for thunderstorm activity will be within the moist unstable boundary
layer off the North Carolina coast,  However, weak elevated
instability may linger ahead of the developing surface low near
coastal areas, perhaps providing support for convection capable of
producing a flash or two of lightning early Sunday.

..Kerr.. 01/02/2021

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