SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CST Wed Feb 16 2022
Valid 171200Z - 181200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
MISSISSIPPI DELTA REGION EASTWARD ACROSS THE TENNESSEE VALLEY...
...SUMMARY...
Severe thunderstorms are expected across portions of the Lower
Mississippi Valley, Mid-South, and Southeast on Thursday.
...Synopsis...
Phasing of a northern-stream upper trough crossing central Canada
and the north-central U.S. with a southern-stream trough crossing
the southern Rockies/southern Plains will occur Thursday, with
eastward progression of the consolidating feature expected. This
system will be characterized by very strong deep-layer flow on its
southeast flank, across the south central into the eastern CONUS.
At the surface, a deepening low is progged to be shifting eastward
out of Oklahoma across the northern Arkansas/far southern Missouri
region through the day, and then northeastward along the Ohio Valley
into the evening hours. A broad, moistening warm sector will exist
across the Mid South and Southeast, until a cold front, advancing
eastward with time, ushers in colder/drier air. This front is
expected to reach the Mississippi Delta region during the afternoon,
the Appalachian crest overnight, and then extend from the
Mid-Atlantic region to the Florida Panhandle by 18/12Z.
...Arklatex region eastward across the Mid South and central Gulf
Coast region...
Widespread showers and embedded thunderstorms will be ongoing at the
start of the period from southeastern Kansas southward to eastern
Oklahoma and Arkansas and into northeastern Texas at the start of
the period, near and ahead of the advancing surface low/cold front.
Meanwhile, largely elevated, warm advection-induced convection will
extend northeastward across the Mid Mississippi and Ohio Valleys and
vicinity. While meager CAPE is expected early in the period, strong
flow aloft suggests that locally damaging wind gusts will be a
possibility from the Arklatex region eastward toward the Mississippi
Delta area through mid afternoon.
With time, deepening of the low and associated strengthening of
low-level southerlies will allow persistent northward theta-e
advection to combine with modest/local diurnal warming, eventually
yielding evolution of mixed-layer CAPE up to about 500 J/kg. Across
Kentucky and areas north, a cool boundary layer should persist,
resulting in slightly stable conditions beneath evolving, modest
instability. However, this thermodynamic concern is partially
offset by stronger ascent aloft spreading across this region --
along with the deepening low expected to track along roughly the
Ohio River through late afternoon and into the evening. With this
ascent likely to maintain partially forced convection, and given
exceptionally strong/veering flow with height across this region,
potential for locally damaging winds and a couple of tornadoes
remains a possibility.
Farther south, greater low-level theta-e advection suggests that the
boundary layer will become at least neutral, and therefore greater
certainty of surface- or near-surface-based storms exists -- both
near the advancing cold front, and also with associated warm
advection-driven bands of convection in the free warm sector. As
noted above, very strong shear -- with south-southwesterly 850 mb
winds in excess of 50 to 60 kt increasing to west-southwesterly at
70 to 90 kt at mid levels -- is suggestive of supercells, and
attendant risk for damaging winds and several -- and possibly
locally strong/damaging -- tornadoes. As such, an upgrade to
enhanced risk is being introduced, centered across the Tennessee
Valley area from late afternoon through the evening hours.
..Goss.. 02/16/2022
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