Missouri threat for severe weather overnight.

Mesoscale Discussion 707
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MESOSCALE DISCUSSION 0707
NWS STORM PREDICTION CENTER NORMAN OK
1018 PM CDT FRI MAY 04 2012

AREAS AFFECTED...EAST CENTRAL MO/SW IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 050318Z - 050445Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...RISK FOR AT LEAST ISOLATED LARGE HAIL/DAMAGING WINDS WILL
INCREASE GRADUALLY THE NEXT FEW HOURS ACROSS ERN MO AND SWRN
IL...WHERE A SEVERE THUNDERSTORM WATCH MAY NEED TO BE CONSIDERED.

DISCUSSION...WAA IS SLOWLY STRENGTHENING IN CONJUNCTION WITH A 30-35
KT SWLY LLJ ACROSS MO...WITH THE WAA FOCUSED ALONG A STALLED FRONT.
A FEED OF MODERATE-STRONG INSTABILITY REMAINS IMMEDIATELY UPSTREAM
OF THIS BOUNDARY...WHICH SUGGESTS THAT STORM COVERAGE WILL LIKELY
INCREASE DURING THE NEXT FEW HOURS. ADDITIONALLY...STORM COVERAGE
COULD BE AIDED OVERNIGHT BY THE APPROACH OF A SHORTWAVE TROUGH FROM
SW MO/NW AR. STEEP MIDLEVEL LAPSE RATES AND MUCAPE OF 2000-3000
J/KG WILL SUPPORT A RISK FOR LARGE HAIL...IN AN ENVIRONMENT WITH
SUFFICIENT VERTICAL SHEAR FOR ORGANIZED MULTICELL CLUSTERS AND SOME
TRANSIENT SUPERCELL STRUCTURES. DAMAGING WINDS COULD ALSO BECOME A
CONCERN ONCE STORM COVERAGE INCREASES AND CELL MERGERS PROMOTE SOME
UPSCALE GROWTH OF CONVECTION. THE ERN MO/SWRN IL AREA WILL CONTINUE
TO BE MONITORED...AND THE SEVERE STORM RISK COULD BECOME SUFFICIENT
TO WARRANT A SEVERE THUNDERSTORM WATCH.