Day 1 Severe Weather Outlook

Valid 021200Z – 031200Z

…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
ARKANSAS EASTWARD ACROSS THE TENNESSEE VALLEY AREA…

…SUMMARY…
Isolated severe thunderstorms are possible from portions of the
Mid-South region southwestward across parts of northeastern Texas
Monday afternoon through early Tuesday morning.

…Synopsis…
As northern-stream upper troughing expands/shifts gradually eastward
across central and eastern Canada and the north-central U.S., an
upper low initially off the southern California coast is progged to
turn eastward with time, reaching northwestern Mexico later in the
period. Meanwhile, fast/low-amplitude westerly to
west-southwesterly flow will prevail over the south-central and
southeastern portions of the country.

At the surface, a cold front initially stretching from the Upper
Great Lakes region southwestward to western Texas will advance
eastward with time, reaching a position from New England to
southeast Texas by the end of the period. This front will focus a
zone of convection from parts of the Ohio and Tennessee valleys into
northeastern Texas from this afternoon into the overnight hours.

…Mid South region southwestward across northeastern Texas…
As the cold front advances gradually southeastward across
Kentucky/Tennessee/Arkansas/northeastern Texas through the day, an
initial area of warm-advection-induced storms will spread eastward
through the Mid South region. In its wake, weak destabilization is
expected ahead of the front, though capping will hinder new storm
development into the afternoon hours.

Substantial model differences exist with respect to the degree of
cap erosion, with HRRR and NAM forecasts the most aggressive models
with elimination of capping by late afternoon, resulting in an
uncapped/amply unstable environment. Given favorable shear across
the region, this thermodynamic evolution would support at least
isolated supercell storms, and attendant severe risk — particularly
in the form of hail. Other/isolated storms are more consistently
forecast by the models southwestward across Arkansas and northern
Louisiana and portions of northeastern Texas.

Based on the consistently more bullish output from NAM/HRRR runs, an
upgrade to slight risk appears reasonable. Primary risk appears to
be hail, but locally damaging winds and even a couple of tornadoes
would be possible should capping erode to the degree depicted in
some guidance. Primary risk appears to exist across the western
Tennessee vicinity in roughly the 23 to 04Z time frame. Marginal
risk is also being extended as far southwestward as northeast Texas,
where a few stronger storms appear likely to initiate during the
afternoon.

..Goss/Nauslar.. 03/02/2020

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