SPC MD 1071

MD 1071 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTHEAST MISSOURI...SOUTHEAST IOWA...NORTHERN ILLINOIS...FAR SOUTHEAST WISCONSIN...AND FAR NORTHWEST INDIANA

Mesoscale Discussion 1071
NWS Storm Prediction Center Norman OK
0244 PM CDT Sat Jun 17 2017

Areas affected...northeast Missouri...southeast Iowa...northern
Illinois...far southeast Wisconsin...and far northwest Indiana

Concerning...Severe potential...Watch possible 

Valid 171944Z - 172145Z

Probability of Watch Issuance...60 percent

SUMMARY...Deepening cumulus/showers developing at this time across
eastern Iowa and northern Illinois are expected to continue evolving
into isolated thunderstorms.  Accompanying risk for locally damaging
winds and hail may require watch issuance.

DISCUSSION...Latest visible satellite loop shows a west-to-east band
of towering cumulus/small Cb developing from just north of MLI to
near ORD, and other deepening in the cu field across far northern
Missouri.  This increase in cumulus development is occurring just
ahead of the slowly advancing cold front (extending from Lake
Michigan southwest across southern Wisconsin/eastern Iowa into
northwest Missouri), where gradual airmass destabilization
continues.

Early afternoon RAOBs from DVN -- and particularly from ILX -- show
a warm troposphere/very weak lapse rates in the 850 to 500 mb layer,
which will limit CAPE development over the next few hours despite a
moist boundary layer and continued heating through broken cloud
cover.  Still, expect continued/gradual increase in the cu field to
result in isolated thunderstorm development over the next 1-2 hours.

With ample shear indicated by area VWPs and the aforementioned 18z
DVN RAOB, owing to mid-level westerly flow currently in the 30 to 40
kt range, a few of the developing cells may organize, and become
capable of producing hail and locally gusty/damaging winds.    While
this development may require WW issuance, greater severe risk is
expected to evolve later this afternoon/early this evening, as a
mid-level short-wave trough/jet streak approaches from the west and
eventually overspreads the area -- yielding an increase in
large-scale ascent and available shear.

..Goss/Weiss.. 06/17/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...IWX...LOT...ILX...MKX...LSX...DVN...DMX...EAX...

LAT...LON   40259295 41079283 42269092 42808786 41688666 41258689
            40838809 39859169 40259295 

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