MESOSCALE PRECIPITATION DISCUSSION 0141
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
312 PM EDT THU JUN 19 2014
 
AREAS AFFECTED...IA, SOUTHERN MN, NORTHWEST IL, AND SOUTHWEST WI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 191911Z - 200111Z
 
SUMMARY...TWO BAND OF CONVECTION WITH HEAVY RAINFALL LIE ACROSS IA
AND ARE ENTERING SOUTHERN MN.  DUE TO SATURATED SOILS, NUMEROUS
INSTANCES OF FLASH FLOODING ARE EXPECTED.  A SIGNIFICANT FLASH
FLOOD EVENT IS POSSIBLE FOR NORTHERN IA, SOUTHERN MN, AND
SOUTHWEST WI WITHIN THE NEXT SEVERAL HOURS.

DISCUSSION...AN OCCLUDED CYCLONE IS CENTERED NEAR THE SD/ND
BORDER, AND CONVECTION IS FORMING NEAR ITS OCCLUSION/TROWAL AND TO
THE NORTH OF THE EFFECTIVE STATIONARY FRONT NEAR THE MO/IA BORDER.
 PRECIPITABLE WATER VALUES ARE 1.75-2", NEAR THE 90TH PERCENTILE
FOR MID TO LATE JUNE AND NO CAPPING APPEARS TO BE PRESENT.  CAPE
VALUES ARE 2000-4000 J/KG.  THE WIND FLOW AT 850 HPA IS INCREASING
AHEAD OF THE APPROACHING FRONTAL ZONE, EXCEEDING THE MEAN 850-400
HPA WINDS, WHICH SHOULD INCREASE PRECIPITATION EFFICIENCY.  THE
CRITERIA FOR THE WET MULTI-CELL ENVIRONMENT HAVE BEEN MET.  FLASH
FLOOD GUIDANCE VALUES ARE EXTREMELY LOW DUE TO DAYS OF HEAVY
RAINFALL ACROSS SOUTHERN MN AND NORTHEAST IA AND CORFIDI VECTORS
WITHIN THIS MOIST ENVIRONMENT ARE LIGHT. THESE FACTORS
SIGNIFICANTLY ELEVATE THE RISK OF FLASH FLOODING.

MUCH OF THE LATEST MESOSCALE GUIDANCE HAS A HANDLE ON THE NEW
ACTIVITY ACROSS WESTERN IA MOVING INTO SOUTHERN MN WHICH SHOULD
MOVE SLOWLY EASTWARD WITH THE FRONTAL ZONE, BUT DOES NOT SEEM TO
CAPTURE ONGOING SLOW-MOVING ACTIVITY ACROSS EASTERN IA DESPITE THE
INCREASING INSTABILITY AND 0-3 KM SHEAR PRESENT.  RAINFALL RATES
UP TO 2.5" AN HOUR ARE POSSIBLE, WHICH WOULD SIGNIFICANTLY EXCEED
FLASH FLOOD GUIDANCE VALUES ACROSS THE REGION.  A SIGNIFICANT
NUMBER OF FLASH FLOOD EVENTS ARE POSSIBLE WITHIN THIS AREA -- THIS
COULD BE A POTENTIALLY DANGEROUS FLASH FLOOD SITUATION FOR MOST OF
THE DEFINED REGION.

ROTH

ATTN...WFO...MKX...DVN...DLH...ARX...MPX...DMX...FSD...OAX...

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

LAT...LON   45219415 43999510 43089533 42039547 41139502 40669435
            40639335 40919230 41059137 41199057 41579021 43249023
            44889091 45759263 45219415