MESOSCALE PRECIPITATION DISCUSSION 0444...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
451 PM EDT WED AUG 12 2015
 
CORRECTED FOR DIRECTION OF PROPAGATION IN 3RD PARAGRAPH

AREAS AFFECTED...NORTHERN MN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 122036Z - 130236Z
 
SUMMARY...CONVECTION HAS BEGUN TO FORM OVER NORTHWEST MN AS CIN
ERODES.  CELL TRAINING SHOULD BECOME AN INCREASING CONCERN WITH
TIME, LEADING TO POSSIBLE FLASH FLOODING.

DISCUSSION...THUNDERSTORMS HAVE BEGUN TO ALIGN ALONG A
NORTH-NORTHWEST TO SOUTH-SOUTHEAST AXIS AS THEY FORM NEAR A WEAK
WARM FRONT-LIKE FEATURE, LOCATED ACROSS WESTERN MN.  MLCAPES IN
THE WARM SECTOR ARE SIGNIFICANT, IN THE 3000-4500 J/KG RANGE
ACROSS EASTERN ND, WITH LESSER VALUES CLOSER TO THE 2000-3500 J/KG
ACROSS WESTERN MN.  PRECIPITABLE WATER VALUES ARE IN THE 1-1.6"
RANGE PER GPS INFORMATION.  INFLOW AT 850 HPA INTO THE BOUNDARY IS
25-30 KTS, ABOVE THE MAGNITUDE OF THE MEAN 850-400 HPA WIND AND AT
A RIGHT ANGLE.

INDIVIDUAL CELLS ARE MOVING EAST-SOUTHEAST AT 20-30 KTS WITH THE
MEAN 850-400 HPA WIND.  STORMS SHOULD CONTINUE TO INTENSIFY AS THE
REMAINING CIN IN THE AREA ERODES AND BACKBUILDING IS POSSIBLE
CONSIDERING THE ORIENTATION OF THE INSTABILITY.  THIS SHOULD ACT
TO LENGTHEN THE CONVECTIVE LINE.  ANY COLD POOL THAT FORMS WOULD
REINFORCE THE WEAK WARM FRONT, WITH CELL MOTION ACCELERATING
TOWARDS 40 KTS AND BECOME MORE PARALLEL TO THE 1000-500 HPA
THICKNESS PATTERN, MOVING MORE TO THE SOUTHEAST AND
SOUTH-SOUTHEAST.  TOWARDS THE END OF THE PERIOD, CONVECTION COULD
BECOME MORE ELEVATED AND THREATEN AREAS FARTHER EAST ACROSS
NORTH-CENTRAL MN.  CELL TRAINING IS THE MAIN FLASH FLOOD THREAT. 
BELIEVE THE 12Z SPC WRF AND NSSL WRF (ALONG WITH 00Z CAM GUIDANCE)
IS HANDLING THIS EVOLUTION THE BEST PER THE AVAILABLE INSTABILITY
AND BREADTH OF THE 850 HPA INFLOW.  HOURLY RAIN RATES UP TO 1.75"
ARE POSSIBLE WHERE CELLS TRAIN, AND BELIEVE THE SPC WRF IN THAT
LOCAL AMOUNTS OF 3-4" ARE POSSIBLE.  FLASH FLOODING IS CONSIDERED
POSSIBLE RATHER THAN LIKELY DUE TO HOW FEW PIECES OF MESOSCALE
GUIDANCE ARE PICKING UP ON THIS ACTIVITY.

ROTH

ATTN...WFO...DLH...FGF...MPX...

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

LAT...LON   49609609 49569536 49299469 48829407 48269362 
            47699364 46799395 46299493 47619604 48889699 
            49579704