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SPC MD 1812

MD 1812 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR SERN IA / NERN MO / W-CNTRL IL

MD 1812 Image


MESOSCALE DISCUSSION 1812
NWS STORM PREDICTION CENTER NORMAN OK
0754 PM CDT THU SEP 17 2015

AREAS AFFECTED...SERN IA / NERN MO / W-CNTRL IL

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 180054Z - 180200Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...AN ISOLD LARGE-HAIL THREAT MAY DEVELOP TO THE EAST OF
SEVERE THUNDERSTORM WATCH 511.  CURRENT THINKING IS THE SEVERE RISK
WILL REMAIN ISOLD ENOUGH TO NOT WARRANT AN ADDITIONAL WATCH.  TRENDS
WILL BE MONITORED.

DISCUSSION...RADAR MOSAIC SHOWS A LEFT AND RIGHT SUPERCELL SPLIT
STRADDLING THE MO/IA BORDER AND MRMS MESH DATA INDICATE SEVERE HAIL
IS OCCURRING WITH THIS PAIR OF STORMS.  THE ACTIVITY LIKELY
DEVELOPED FROM MID-LEVEL CONVECTION AND BECAME SURFACE-BASED OVER
THE PAST FEW HOURS.  COOLING DUE TO THE LOSS OF DAYTIME HEATING OVER
THE NEXT 1-3 HOURS WILL PROBABLY LEAD TO A DECOUPLING OF THE
BOUNDARY LAYER AND SERVE TO SLOWLY WEAKEN THE EXISTING ACTIVITY. 
NONETHELESS...A FEED OF STEEP LAPSE RATES FROM THE WEST IN THE -10
TO -30 DEG C LAYER /REFERENCE THE 18/00Z TOP RAOB/ AND SUFFICIENT
SHEAR FOR ORGANIZED STORMS WILL LEND SOME POTENTIAL FOR A LARGE-HAIL
RISK MOVING BEYOND THE EASTERN BOUND OF SEVERE THUNDERSTORM WATCH
511.  WHILE AN ADDITIONAL SEVERE THUNDERSTORM WATCH APPEARS
UNLIKELY...WILL MONITOR OBSERVATIONAL TRENDS OVER THE NEXT 1-3
HOURS.

..SMITH/EDWARDS.. 09/18/2015

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LSX...DVN...

LAT...LON   40029226 41149197 41349126 41139097 40149137 39899186
            40029226 

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from SPC Mesoscale Discussions http://1.usa.gov/1OAMUDf

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