SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1127 AM CST Thu Dec 31 2020

Valid 011200Z - 021200Z


Thunderstorms associated with isolated severe wind gusts and a
marginal tornado threat will be possible on Friday from the Florida
Panhandle northward to the Ohio Valley and northeastward into South

Split flow aloft will persist across the U.S. Friday.  An upper low
in the southern stream -- initially forecast over Oklahoma -- will
shift quickly northeastward into the Midwest with time, gradually
becoming re-absorbed into the northern stream of westerlies through
the end of the period.  Meanwhile, a second low in the southern
stream -- initially over northwestern Mexico -- will progress
steadily east-northeastward into the southern Plains through the

At the surface, a low over the eastern Oklahoma/Arkansas vicinity
Friday morning will move northeastward across the Ozarks through the
day, and then continue northeastward through the evening and
overnight, reaching the Lower Great Lakes Saturday morning.  A cold
front trailing from this low is forecast to advance slowly eastward
across the central Gulf Coast states/Mid South region through the
first half of the period, and then approach/reach the central and
southern Appalachian crest by the end of the period.  East of the
mountains, a cold air dam/wedge front lying across northern Georgia
and South Carolina will linger in place through the day, before
weakening overnight as low-level southerly flow evolves across the
East Coast states ahead of the advancing cold front.

...Kentucky/Tennessee south to the Florida Panhandle...
Showers and isolated thunderstorms are forecast to be ongoing at the
start of the period, from near the Missouri/Illinois border
south-southeast across western Tennessee and into eastern
Mississippi/western Alabama, in the vicinity of the cold front. 
Ahead of the front, weak lapse rates and widespread cloud cover --
plus scattered, warm-advection-induced convection will substantially
limit warm-sector instability.  Still, favorably strong deep-layer
flow, and veering in the low-level wind field -- particularly with
northward extent -- will support potential for a few
organized/rotating storms.  While severe potential should remain
subdued given the thermodynamic deficiencies, a couple of locally
damaging gusts, or a tornado or two, cannot be ruled out.

...Georgia and South Carolina vicinity...
Showers and scattered thunderstorms are forecast to be ongoing over
portions of the area at the start of the period, and will persist
through the afternoon and into the evening, within a persistent zone
of warm advection ahead of the cold front.  Given weak lapse rates
and widespread precipitation and associated cloud cover, minimal
destabilization potential is noted.  Still, with strong deep-layer
flow across the region, a few stronger storms -- capable of gusty
winds possibly nearing or reaching severe levels, may occur.  In
addition, limited potential for a tornado or two may also evolve,
perhaps greatest near the remnant wedge front where low-level
vorticity would be maximized.  Severe risk will eventually diminish
into the overnight hours, as weak short-wave ridging -- and
associated large-scale subsidence/warming aloft evolves across the
Southeast through the end of the period.

..Goss.. 12/31/2020

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