SPC AC 190559
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1159 PM CST Sat Feb 18 2017
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWEST
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHERN GREAT
Isolated severe thunderstorms are possible across parts of the
southern Great Plains on Sunday and Sunday night.
A strong low-latitude, mid-level trough will move east across the
southern Rocky Mountains into the central United States on Sunday
and Sunday night. As the larger-scale trough moves east, a lead
shortwave trough will lift northeast from northern Mexico into the
central United States, dragging a weak surface front across Oklahoma
...Southern Great Plains...
Widespread low-level clouds are expected through much of the day as
moisture is drawn northward ahead of the aforementioned ejecting
shortwave trough. Despite weak insolation, steepening
mid-level-lapse rates and increasing low-level moisture will result
in gradual destabilization across much of Texas and Oklahoma.
Despite most unstable CAPE values up to 1000 J/kg by late afternoon
across northwest Texas and southwest Oklahoma, uncertainty exists as
to whether thunderstorms can initiate as strongest forcing will
remain west of the area. If thunderstorms can initiate, deep-layer
shear around 50 knots will support supercell structures with an
attendant hail threat. Weak low-level wind fields across this area
should act to limit the overall tornado/wind threat.
By late evening into the overnight hours, increasing forcing for
ascent should begin to overspread much of the southern Great Plains
resulting in an increase in thunderstorm coverage. Expectation is
that this activity would be elevated in nature, favoring a linear
mode, given the decreasing instability and increasingly linear
forcing. Isolated large hail or damaging wind gusts would be the
primary overnight threat as this activity moves east.
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