SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1140 PM CST Wed Feb 10 2021

Valid 111200Z - 121200Z


A couple of strong thunderstorms may impact parts of the Georgia
into South Carolina Piedmont late this afternoon and evening,
accompanied by at least some risk for severe weather.

Models indicate that lowest mid-level heights will gradually
consolidate near/north of the North Dakota/Minnesota international
border area during this period.  Beneath broadly confluent flow to
the south of this feature, across and to the lee of the Rockies, it
appears that cold high pressure, characterized by Arctic air, will
become increasingly entrenched across much of the Great Plains and
Mississippi Valley.  By late tonight into early Friday, cold high
pressure is also forecast to build southward to the lee of the
southern Appalachians.

At the same time, mid-level subtropical ridging likely will maintain
an influence across much of the eastern Gulf of Mexico and
Southeast.  However, it appears that the high center near the
Bahamas is weakening, and a series of short wave perturbations,
emanating from larger-scale troughing now digging across parts of
the Southwest and Baja, may contribute to suppression of mid-level
heights across the Tennessee Valley/southern Appalachians vicinity. 

The large-scale trough is forecast to continue digging into the
Mexican Plateau into early Friday, as a vigorous upstream
perturbation (emanating from the mid-latitude Pacific) digs inland
across the California coast.

Around the northern periphery of the subtropical ridge, and ahead of
the lead upstream troughing, a moistening southerly return flow is
expected to continue off the Gulf of Mexico into much of the Gulf
and south Atlantic Coast states.  Across much of Texas into the
lower Mississippi/Tennessee Valleys and southern Mid Atlantic
region, this will generally be maintained above the slowly southward
advancing, shallow leading edge of the Arctic air mass.  However,
aided by forcing for ascent associated with the short wave
perturbations, destabilization aloft is expected to be sufficient
for scattered areas of generally weak thunderstorm activity.

...Georgia/South Carolina Piedmont...
Models do suggest that one short wave perturbation may be
accompanied by weak surface frontal wave development across central
Alabama into the Georgia Piedmont by this afternoon, where warm
sector boundary-layer warming and dew points in the lower 60s may
contribute to CAPE on the order of 500 J/kg.  Guidance suggests that
this may coincide with strengthening southwesterly to westerly
lower/mid tropospheric flow near the front, ahead of the frontal
wave, including speeds on the order of 30-50 kt in the 850-500 mb
layer.  It appears that this environment could become at least
marginally conducive to vigorous thunderstorms with occasional
supercell structures.  These may be accompanied by the risk for
small to marginally severe hail and potentially damaging wind gusts,
and spread into the South Carolina Piedmont before diminishing this

..Kerr.. 02/11/2021

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