SPC MD 1591

MD 1591 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR SOUTHERN IOWA AND NORTHERN MISSOURI

MESOSCALE DISCUSSION 1591
NWS STORM PREDICTION CENTER NORMAN OK
0622 PM CDT SUN AUG 02 2015

AREAS AFFECTED...SOUTHERN IOWA AND NORTHERN MISSOURI

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 022322Z - 030015Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THUNDERSTORMS ARE DEVELOPING ALONG A COLD FRONT WITHIN A
VERY UNSTABLE ATMOSPHERE. LARGE HAIL AND DAMAGING WINDS WILL BE
POSSIBLE WITH THE STRONGEST THUNDERSTORMS. HOWEVER...THIS THREAT IS
EXPECTED TO DIMINISH AFTER THE NEXT 2-3 HOURS. AS SUCH...A WATCH IS
NOT ANTICIPATED AT THIS TIME...BUT WILL CONTINUE TO BE ASSESSED.

DISCUSSION...THUNDERSTORMS ARE DEVELOPING/STRENGTHENING...ALONG A
SLOWLY SOUTHWARD-MOVING COLD FRONT. AHEAD OF THE COLD
FRONT...SURFACE TEMPERATURES HAVE WARMED INTO THE UPPER-80S TO
LOW-90S F WITH DEW POINT TEMPERATURES IN THE LOW-T0-MID 70S F.
THIS...COUPLED WITH STEEP MID-LEVEL LAPSE RATES HAVE COMBINED TO
YIELD MUCAPE VALUES ABOVE 4000 J/KG. ADDITIONALLY...THIS AREA IS ON
THE SOUTHERN EDGE OF THE STRONGER MID-LEVEL FLOW RESULTING IN
DEEP-LAYER SHEAR VALUES ON THE ORDER OF 35 KTS. THE COMBINATION OF
CAPE AND DEEP-LAYER SHEAR IN THE PRESENCE OF CONVERGENCE ALONG THE
SURFACE-COLD FRONT WILL SUPPORT CONTINUED THUNDERSTORM DEVELOPMENT
IN THE NEAR TERM...WITH LARGE HAIL/DAMAGING WINDS POSSIBLE WITH THE
STRONGEST THUNDERSTORM CORES. 

HOWEVER...CONVERGENCE ALONG THE COLD FRONT IS EXPECTED TO WEAKEN
WITH TIME...AND THE LOSS OF DAY-TIME HEATING AND LOWER SURFACE DEW
POINT TEMPERATURES TO THE SOUTH /ACROSS MISSOURI/ WILL CONTRIBUTE TO
A WEAKENING OF THE OVERALL INSTABILITY. AS SUCH...IT APPEARS THERE
MAY ONLY BE A BRIEF WINDOW OF OPPORTUNITY FOR THUNDERSTORMS TO HAVE
A SUSTAINED LARGE HAIL/DAMAGING WIND THREAT. A WATCH IS NOT
ANTICIPATED AT THIS TIME...ALTHOUGH TRENDS WILL CONTINUE TO BE
ASSESSED.

..MARSH/CORFIDI.. 08/02/2015

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

ATTN...WFO...LSX...DVN...DMX...EAX...OAX...TOP...GID...

LAT...LON   41169762 41509674 41799335 41619202 40909148 40129165
            39879332 39889541 40339703 40629771 41169762 

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