MESOSCALE PRECIPITATION DISCUSSION 0083
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
952 AM EDT SAT MAY 31 2014
 
AREAS AFFECTED......CENTRAL MN TO NORTHWEST WI... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 311350Z - 311950Z
 
SUMMARY...SHOWERS AND THUNDERSTORMS ARE EXPECTED TO PERSIST ACROSS
CENTRAL MN AND NORTHWEST WI OVER THE NEXT SEVERAL HOURS.  RAINFALL
RATES OF 1-2" AN HOUR IN HEAVIER STORMS COULD CAUSE FLASH FLOODING
WHERE CELLS TRAIN.

DISCUSSION...AN AREA OF SHOWERS AND EMBEDDED THUNDERSTORMS HAS
DEVELOPED NEAR WHAT WAS ONCE AN OUTFLOW BOUNDARY AND NOW APPEARS
TO BE A MESOSCALE BAROCLINIC ZONE AS HEATING OCCURS SOUTH OF THE
BNDRY...AND ASCENT OCCURS OVER THE LOW LEVEL BNDRY.   

MORNING SOUNDINGS IN THE REGION SHOW DEEP MOISTURE WITH THE
MINNEAPOLIS RAOB INDICATING MEAN LAYER RH OF 77 PERCENT.
THE SOUNDING DEEP LAYER CAPE WAS 1605 J/KG WHICH WAS WELL ABOVE
THE 500-750 J/KG IN THE HIGH RES RAPID REFRESH ANALYSIS AND SHORT
TERM FORECAST. 
THE SOUNDING WINDS WERE FROM THE SOUTH-SOUTHWEST WITH LITTLE
DIRECTIONAL SHEAR BELOW 500 MB. THIS RESULTED IN AREAS WHERE CELLS
HAVE TRAINED. 
NEW CELLS ARE FORMING UPSTREAM...LEADING TO POTENTIAL FOR MORE
TRAINING AND LOCALLY HEAVY RAINS.

WITH PRECIPITABLE WATER VALUES NEAR 1.6" AND FORECAST TO CREEP UP
THIS AFTERNOON ALONG WITH 850-700 MB MOISTURE FLUX ANOMALIES 1-2
STD DEVIATIONS ABV NORMAL...THE PERSISTENCE OF SHOWERS AND STORMS
LEADS TO A FLOOD THREAT.  

RAINFALL RATES IN STRONGER CELLS ARE EXPECTED TO REACH 1-2" AN
HOUR, WITH AMOUNTS POTENTIALLY REACHING 2-3" OVER THE NEXT SEVERAL
HOURS.  THIS IS SUPPORTED BY BANDING EVIDENT IN THE HIGH RES
MODELS LIKE THE WRF ARW...WRF NMM...SPC WRF AND NSSL WRF...AS WELL
AS THE HIGH RES RAPID REFRESH.

PETERSEN

ATTN...WFO...DLH...MPX...FSD...ABR...

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

LAT...LON   44829645 46419359 47259192 46989138 46569151 46079177
            45509260 44829449 44399619 44599658 44809650 44829645