SPC AC 221244
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0744 AM CDT Sun Sep 22 2019
Valid 221300Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF OK
TO IL THROUGH THIS EVENING...
Isolated damaging winds, and perhaps a tornado or two, will be
possible through this evening from parts of Oklahoma to Illinois.
...OK to IL through this evening...
A midlevel shortwave trough with embedded perturbations over the
central/northern High Plains will progress eastward to the MS Valley
and Great Lakes by tonight. In advance of an embedded speed max
over the central High Plains, an associated weak surface cyclone in
KS this morning will develop northeastward along a front toward
Lower MI by early tonight. A narrow corridor of richer low-level
moisture, ranging from upper 60s dewpoints into IL to lower 70s in
OK, will be maintained immediately in advance of the weak low and
cold front today.
A somewhat complex scenario will evolve today with widespread
ongoing rainfall and some embedded thunderstorms from OK to WI.
Outflow from overnight convection and differential heating today
will maintain the effective boundary from northern IL into central
MO. An embedded MCV is moving northeastward over southeast KS this
morning, and per local VWPs and model forecasts, a 50 kt low-level
jet will develop northeastward today with the weak frontal wave and
ejecting midlevel trough. Though widespread rainfall will continue
to limit lapse rates, the rich low-level moisture and pockets of
surface heating in cloud breaks will support MLCAPE ranging from 500
J/kg this afternoon in IL to 1500 J/kg in OK. Enhanced low-midlevel
flow/shear along the effective surface boundary, potentially
augmented by the remnant MCV moving from KS to MO, may support some
embedded rotating storms and/or small bowing segments. The threat
for isolated damaging winds and a tornado or two will begin the
first half of the day from southeast KS into OK, and continue into
late afternoon/evening into IL.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z