SPC AC 231240
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0740 AM CDT Sat Sep 23 2017
Valid 231300Z - 241200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS UPPER MIDWEST TO
SOUTHERN HIGH PLAINS...
Isolated severe wind and hail will be possible from the Upper
Midwest to the southern High Plains, mainly this afternoon and early
A highly amplified upper pattern will persist with a cyclone over
the Great Basin and anticyclone over the Midwest. Surface features
will remain quasi-stationary over the central states with a cyclone
anchored across east-central CO and attendant front arcing northeast
into the Upper MS Valley.
...Upper Midwest to central Great Plains...
Elevated, largely non-severe convection will likely persist
north/west of the front through much of the period. Isolated to
scattered storms should develop near the front towards peak heating.
A residual plume of modestly steep mid-level lapse rates should
yield a moderately unstable air mass with MLCAPE of 1000-2000 J/kg.
With quasi-meridional deep-layer winds, surface-based convection
will tend to emanate along and north of the boundary. Effective
shear in excess of 30 kt should be confined along and north of the
front as well. As such, severe wind/hail coverage will most likely
be isolated and diminish after sunset.
...Southern High Plains...
Moist, upslope flow is already contributing to scattered storms
across northeast NM. Although diabatic heating should be modest,
MLCAPE of 500-1000 J/kg will be maintained. Some increase in
mid-level winds is anticipated with gradual eastward progression of
the Great Basin upper low, however deep-layer flow will remain
meridional. Amid scattered to widespread storms this afternoon and
early evening, a few linear segments should form and slowly shift
east, offering a risk for isolated severe wind gusts.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z