MESOSCALE PRECIPITATION DISCUSSION 0388
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1052 AM EDT SUN JUL 26 2015
 
AREAS AFFECTED...NORTHEAST IA...NORTHWEST IL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 261445Z - 261745Z
 
SUMMARY...VERY INTENSE SHORT-TERM RAINFALL TOTALS ARE EXPECTED
WHICH MAY RESULT IN SOME FLASH FLOODING THE NEXT COUPLE OF HOURS.

DISCUSSION...GOES-RGB AIRMASS IMAGERY SHOWS A WELL-DEFINED PV
ANOMALY/VORT CENTER MOVING ACROSS SOUTHEAST MN AND NORTHEAST IA
THIS MORNING. THIS IS HELPING TO FOCUS A RATHER CONCENTRATED AREA
OF VERY HEAVY SHOWERS AND THUNDERSTORMS JUST NORTH OF A WAVE OF
LOW PRESSURE THAT IS ADVANCING EAST ALONG A FRONTAL ZONE. CLOUD
TOPS OVER THE LAST HOUR HAVE COOLED A TAD SUGGESTING AN UPTICK IN
VERTICAL ASCENT.

IN ADDITION TO DEEPER FORCING ASSOCIATED WITH THE VORT
CENTER...THE CONVECTION APPEARS TAKING ADVANTAGE OF AN AXIS OF
STRONG MOISTURE CONVERGENCE NEAR AND JUST NORTH OF THE LOW CENTER.
INSTABILITY ON THE OTHER HAND IS QUITE MODEST WITH ONLY 500 J/KG
TO 1000 J/KG OF CAPE FOCUSED OVER THE REGION.

PWATS ARE THE REGION HAVE NOSED UP TO 1.8 TO 1.9 INCHES OVER
NORTHEAST IA AS PER LATEST GPS-DERIVED DATA...AND SO RAINFALL
RATES ARE EXPECTED TO BE LOCALLY VERY INTENSE. THE CONVECTION IS
RATHER SLOW-MOVING AS WELL AND AS SUCH IS CAPABLE OF PRODUCING
LOCALLY ENHANCED RAINFALL TOTALS GIVEN THE AFOREMENTIONED RATES.
DESPITE RATHER HIGH FFG VALUES...THE INTENSE SHORT-TERM RAINFALL
POTENTIAL MAY BE ENOUGH TO DRIVE A SMALL SCALE FLASH FLOOD THREAT.

THE CONVECTION SHOULD TEND TO WEAKEN THOUGH AFTER 18Z OWING TO A
DRIER AND RELATIVELY MORE STABLE AIRMASS DOWNSTREAM OF THE VORT
ENERGY. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...ARX...DVN...LOT...MKX...

ATTN...RFC...NCRFC...

LAT...LON   42759085 42398983 41908925 41488986 41689070 
            42369147 42649144