MESOSCALE PRECIPITATION DISCUSSION 0446
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
455 AM EDT THU JUL 06 2017

AREAS AFFECTED...EASTERN MN...NORTHWEST WI

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 060850Z - 061200Z

SUMMARY...CLUSTER OF SLOW-MOVING THUNDERSTORMS WITH INTENSE
RAINFALL RATE MAY PERSIST FOR A COUPLE MORE HOURS BEFORE THEN
ADVANCING SOUTHEAST. ADDITIONAL FLASH FLOODING IS LIKELY.

DISCUSSION...A CLUSTER OF VERY COLD-TOPPED THUNDERSTORMS OUT AHEAD
OF A PROGRESSIVE UPSTREAM MCS IS IMPACTING PORTIONS OF EASTERN MN
WITH A STRONG FOCUS ON KANABEC AND AITKIN COUNTIES. ALREADY VERY
HEAVY RAINS HAVE OCCURRED AND ADDITIONAL HEAVY RAINFALL IS
EXPECTED OVER THE NEXT 1 TO 2 HOURS WITH A GRADUAL TENDENCY FOR
THE CONVECTIVE CLUSTER TO ADVANCE SOUTHEAST AND JUST TO THE
NORTHEAST OF A WARM FRONT.

THE AIRMASS POOLED ALONG THE WARM FRONT IS QUITE UNSTABLE AND
MOIST WHICH IS PROVIDING A THERMODYNAMICALLY FAVORABLE ENVIRONMENT
FOR CONVECTION. MEANWHILE...WARM ADVECTION IS BEING SUSTAINED WITH
SOUTHWEST FLOW OUT AHEAD OF AN UPSTREAM SHORTWAVE TROUGH AND WAVE
OF LOW PRESSURE ACROSS CENTRAL ND.

THE LATEST AVAILABLE HIRES GUIDANCE IS DOING A TERRIBLE JOB IN
HANDLING THE CONVECTIVE EVOLUTION ACROSS THE REGION HERE...WITH
THE ARW/NMMB SOLUTIONS TOO FAR NORTH...AND EVEN THE HRRR GUIDANCE
TOO LIGHT WITH ITS AMOUNTS.

THE CONVECTION WILL STILL IMPACT AREAS OF EASTERN MN FOR ANOTHER 1
TO 2 HOURS...BUT SHOULD ADVANCE SOUTHEAST INTO PARTS OF NORTHWEST
WI TOO AND GENERALLY ALONG AND JUST NORTH OF THE WARM FRONT.
EXPECT RAINFALL RATES OF UP TO 2.5 INCHES/HR...WITH STORM TOTALS
LOCALLY IN EXCESS OF 5+ INCHES WHERE THE STORMS TEND TO HANG UP
AND BACKBUILD OVER THE SAME AREA GIVEN THE FAVORABLY
MOIST/UNSTABLE SOUTHWEST FLOW INTERACTING WITH THE FRONT. THE
UPSTREAM MCS ARRIVING FROM NORTHWEST MN WILL EVENTUALLY MERGE WITH
THE CONVECTIVE CLUSTER ALONG THE WARM FRONT...AND THIS WILL
CONTRIBUTE TO SOME CELL MERGER ACTIVITY WITH FURTHER ENHANCED
RAINFALL RATES POSSIBLE. EXPECT ADDITIONAL FLASH FLOODING CONCERNS
AS A RESULT OVER THE THREAT AREA.

ORRISON

ATTN...WFO...ARX...DLH...MPX...

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

LAT...LON   46679352 46649266 46219150 45839085 45479073
            45139119 45249195 45519295 45829353 46239387