MESOSCALE PRECIPITATION DISCUSSION 0312
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EDT SUN JUN 17 2018

AREAS AFFECTED...NORTHEAST/CENTRAL MN...NORTHWEST WI...WESTERN
U.P. OF MI...

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

VALID 171800Z - 172300Z

SUMMARY...HIGH RAINFALL RATES MOVING THROUGH FLOODED REGIONS
LIKELY TO INDUCE ADDITIONAL FLASH FLOODING RISK THROUGH

DISCUSSION...A SUBTLE SPEED MAX AND ASSOCIATED SHORTWAVE ARE
PASSING ACROSS NORTHERN MN INTO SW ONT ATTM SUPPORTING SUFFICIENT
MID-LEVEL ASCENT TO SPARK SOME ANAFRONTAL CONVECTION ACROSS
CENTRAL TO NORTHEAST MN. A WEAK SFC WAVE EXISTS NEAR KSTC WITH THE
FRONT EXTENDING TOWARD KDLH INTO LAKE SUPERIOR. SOUTHEAST OF THE
FRONT, RECENT RAP ANALYSIS DEPICTS STRONG INSTABILITY BUT REMAINS
CAPPED IN THE SHORT-TERM BUT GIVEN SFC WAVE, MULTI-DIRECTIONAL SFC
MST CONVERGENCE/CONFLUENCE MAY BE SUFFICIENT TO BREAK THE CAP
ESPECIALLY IF ANAFRONTAL CONVECTION KICKS A SOUTHEASTWARD SAGGING
OUTFLOW STRENGTHENING FGEN IN THE REGION.  INSTABILITY HAS ALREADY
BUILT TO 3000 J/KG SBCAPES ACROSS SOUTHERN AND CENTRAL
MN...FEEDING TOWARD THIS REGION WHERE CAPPED VALUES ARE ALREADY
NEAR 1250 J/KG. 

TRENDS ON THE ANAFRONTAL CONVECTION ARE COOLING/EXPANDING TAPPING
SOME OF THE VERY HIGH MOISTURE IN THE ENVIRONMENT TO SUPPORT RAIN
RATES OF 1.0-1.5"/HR, THOUGH EASTWARD PROPAGATION IS ADDING TO
FAIRLY SOLID EASTWARD CELL MOTIONS AT THIS TIME.  STILL THE CELLS
ARE MOVING INTO AREAS OF COMPROMISED SOIL CONDITIONS THAT ARE
ALREADY SATURATED TO SIGNIFICANT DEPTH TO ALLOW FOR HYDROPHOBIC
RUNOFF CONDITIONS FAIRLY QUICKLY THAT FFG VALUES OF .3-.5"/HR
COULD BE EXCEED QUICKLY ACROSS AITKIN/CARLTON COUNTIES IN MN AND
LESS THAN 1" EVEN FURTHER WEST TOWARD CROW WING EVEN IN THE SHORT
TERM.  YET WITH REDUCTION OF CAP, INCREASED INSTABILITY OVER THE
NEXT FEW HOURS THE BULK OF HI-RES CAM GUIDANCE BREAKS OUT
CONVECTION IN THE WARM SECTOR ACROSS THE DISCUSSED REGION TOWARD N
WI...LEADING TO LIKELY FLASH FLOODING GIVEN RATES OF 1.5-2"/HR
WOULD INCREASINGLY BECOME MORE COMMON.   CELL MOTIONS TO THE EAST
MAY REDUCE THE THREAT...BUT GIVEN ORIENTATION OF CELL MOTIONS TO
THE REINFORCING FGEN FROM NORTHEASTERLY FLOW OF LAKE SUPERIOR,
CELLS HAVE A GOOD POSSIBILITY TO ORIENT FAVORABLY FOR TRAINING
AFTER 21-22Z OVER FFG VALUES BELOW .5"/HR ACROSS N WI INTO WESTERN
U.P. OF MI.  AS SUCH FLASH FLOODING IS CONSIDERED LIKELY THROUGH
23Z WITH 2-3" TOTALS LIKELY.

GALLINA

ATTN...WFO...DLH...GRB...MPX...MQT...

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

LAT...LON   47418828 47248812 46508799 46088867 46088916
            45998971 45529015 45549146 45579250 45649343
            45769391 46099434 46489381 46809292 46849190
            47069111 47119043 46929020 46869009 47128919
            47288878