SPC AC 111248
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CST Thu Mar 11 2021
Valid 111300Z - 121200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT
FROM SOUTHERN IL/MO WESTWARD NEAR THE KS/OK BORDER...
...SUMMARY...
A few locally strong wind gusts and hail are possible today from
southern Missouri to southern Illinois, and isolated large hail will
be possible late tonight near the Oklahoma/Kansas border.
...Synopsis...
A midlevel shortwave trough over the upper Great Lakes will continue
eastward to New England by tonight, as a surface cold front in its
wake drifts slowly southward across the lower OH Valley and the
southern Plains. Farther west, a large closed low near the central
CA coast will move slowly inland to the lower CO Valley by Friday
morning. Modest midlevel height rises are expected with
low-amplitude shortwave ridging over the southern Plains and Ozarks
through tonight.
Gradual air mass modification and northward moisture return will
persist through the period from the western Gulf of Mexico to OK/AR
along the slow-moving front. Frontogenesis and low-level warm
advection atop the frontal surface will support convection along and
to the cool side of the boundary from MO into the OH Valley through
the period. MUCAPE approaching 1000 J/kg, effective bulk shear of
40-50 kt, and midlevel lapse rates of 7-8 C/km will support a
low-end threat for large hail and damaging winds with organized
clusters/isolated supercells along and just north of the front.
Farther west, only weak forcing for ascent and lingering convective
inhibition suggest that storm development to the warm side of the
cold front is unlikely today. Elevated thunderstorm development is
expected generally north of I-40 from the TX Panhandle and OK into
southern KS as low-level warm advection increases. Steep lapse
rates and MUCAPE of 500-1000 J/kg may be sufficient for isolated
large hail late tonight near the OK/KS border.
..Thompson/Mosier.. 03/11/2021
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