MESOSCALE PRECIPITATION DISCUSSION 0445
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1049 PM EDT WED AUG 12 2015
 
AREAS AFFECTED...NORTHERN MINNESOTA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 130248Z - 130748Z
 
SUMMARY...SMALL COMPLEX WITHIN MOIST ENVIRONMENT FOR HIGHLY
EFFICIENT RAINFALL RATES POTENTIALLY TRAINING OVER TRACK OF
EARLIER COMPLEX

DISCUSSION...INCREASING LOW LEVEL JET TO 30-35 KTS AT 85H WILL
LIFT ISNETROPICALLY OVER EFFECTIVE FRONT LAID OUT BY OUTFLOW FROM
EARLIER COMPLEXES ACROSS NORTHER MN.  INSTABILITY AND MOISTURE
FIELDS BEING ADVECTED BY THE LLJ FROM SOUTHERN ND/SD ARE QUITE
IMPRESSIVE WITH MUCAPES IN EXCESS OF 4000 J/KG AND TOTAL PWATS IN
THE 1.75" RANGE.  THIS WILL MAKE FOR HIGHLY EFFICIENT RAINFALL
PRODUCTION AS SEEN WITH CELLS MOVING OUT OF MARSHALL INTO
PENNINGTON COUNTY...WITH RATES OF 2-2.5"/HR.  WITH LOW LEVEL
RETURN FROM THE SOUTH-SOUTHEAST EAST OF THE OUTFLOW
BOUNDARY...INCREASED LOW LEVEL SHEAR SHOULD SUPPORT RIGHT MOVING
CELLS...WITH RAP FORECAST FORWARD PROPAGATION VECTORS OF 5 TO 10
KTS...THIS SHOULD COMPOUND TOTALS IN THE 2-3" RANGE.  IT IS ALSO
POSSIBLE GIVEN CELL MOTION VECTORS...THAT THE CELLS MAY REPEAT
OVER THE TRACK OF EARLIER RAINFALL INCREASING FLASH FLOOD THREAT. 

THE LOW LEVEL JET SHOULD REMAIN NICELY ORIENTED (NEAR
PERPENDICULAR) WITH THE ISENTROPIC BOUNDARY THROUGHOUT THE NEXT
4-6HRS VEERING FROM SOUTHWEST TO WEST WITH THE SOUTHWARD
PROGRESSION OF THE COLD FRONT...STILL RETAINING A HIGH GRADIENT TO
MAINTAIN STRONG FLOW FOR MOISTURE CONVERGENCE.   THIS CONVERGENCE
IS LIKELY TO ENHANCE CONVECTIVE INITIATION ALONG THE BOUNDARY
LEADING TO ADDITIONAL CELLS FOR TRAINING AND POSSIBLE MERGERS AS
THE MAIN COMPLEX MOVES SOUTH.  FLOW IS FORECAST TO WEAKEN FROM 30
TO 20 KTS AT 85H AROUND THE 09-11Z TIME FRAME.  

GALLINA

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

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

LAT...LON   48419567 47879431 47229348 46129329 45669430 
            46199526 46699582 47619648 47989676 48339659