MESOSCALE PRECIPITATION DISCUSSION 0477
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
922 PM EDT SAT SEP 05 2015
 
AREAS AFFECTED...CENTRAL AND NORTHEAST MN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 060115Z - 060600Z
 
SUMMARY...STRONG CONVECTION WITH INTENSE RAINFALL RATES BECOMING
BETTER ORGANIZED AND EXPANDING IN COVERAGE. TRAINING CELLS WILL
FOSTER INCREASING POTENTIAL FOR FLASH FLOODING.

DISCUSSION...IR SATELLITE IMAGERY SHOWS RAPIDLY COOLING CONVECTIVE
CLOUD TOPS WITH EMBEDDED OVERSHOOTING TOPS OVER CENTRAL
MN...GENERALLY JUST WEST OF A LINE FROM LITTLE FALLS TO BRAINERD.
THE CONVECTION IS BECOMING INCREASINGLY CONCENTRATED AND IS
ORGANIZED WITH A MOTION OFF TO THE NORTHEAST OUT AHEAD OF A
SHORTWAVE TROUGH MOVING ACROSS NORTHEAST SD. THE APPROACHING
SHORTWAVE IS FOSTERING EXTENSIVELY DIFFLUENT FLOW ALOFT...AND THE
DYNAMICS ARE INTERACTING WITH A VERY MOIST AND MODERATELY UNSTABLE
AIRMASS ACROSS THE UPPER MS VALLEY. A NOSE OF MLCAPES EXCEEDING
2500 J/KG EXTEND THROUGH CNTRL MN...AND WITH GOES-SOUNDER PWATS
CLOSE TO 2 INCHES WHICH IS VERY IMPRESSIVE FOR EARLY SEPTEMBER AND
CLOSE TO 3 STD DEV ABOVE NORMAL. COORDINATION WITH NESDIS/SAB
CONFIRMS THESE OBSERVATIONS.

THE CONVECTION IS DEVELOPING IN AN ENVIRONMENT CONDUCIVE FOR
TRAINING GIVEN THE SW/NE ORIENTATION OF THE ACTIVITY...AND DEEPER
LAYER SW FLOW THAT IS ALREADY SET UP OVER THE REGION.
UNFORTUNATELY THE HIRES MODEL GUIDANCE IS NOT HANDLING THE CURRENT
CONVECTIVE EVOLUTION WELL. CONSECUTIVE RUNS OF THE HRRR HAVE BEEN
INSISTING ON THE CONVECTIVE BANDS DEVELOPING FARTHER NORTH...AND
THE 12Z ARW AND 12Z NMMB HAVE BEEN WAY TOO DRY/DISMISSIVE OF MUCH
OF THE CONVECTION THAT HAS EVOLVED THIS EVENING ACROSS THE UPPER
MS VALLEY.

GIVEN THE SHORTWAVE DYNAMICS ARRIVING FROM NORTHEAST SD AND THE
INTERACTION WITH SUCH FAVORABLE MOISTURE AND INSTABILITY
PROFILES...THE ONGOING CONVECTION SHOULD TEND TO EXPAND IN
COVERAGE AND TO AN EXTENT IN INTENSITY. THE HIGH PWATS OF NEAR 2
INCHES WILL FAVOR VERY INTENSE RAINFALL RATES. THIS COUPLED WITH
THE RISK FOR TRAINING CELLS WILL SUPPORT VERY HEAVY RAINFALL
TOTALS THAT MAY LOCALLY APPROACH 5 INCHES. FLASH FLOODING IS
POSSIBLE AS A RESULT.

ORRISON

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

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

LAT...LON   48089170 47529104 46449250 45779421 45689515 
            46199550 46799490 47509362