MESOSCALE PRECIPITATION DISCUSSION 0457
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
229 AM EDT TUE JUL 12 2016
 
AREAS AFFECTED...NORTHWEST AND CENTRAL WI...UP OF MI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 120630Z - 120930Z
 
SUMMARY...UPSTREAM THUNDERSTORMS FROM SOUTHEAST MN AND NORTHEAST
IA WILL MERGE WITH THE SOUTHERN EXTENT OF CONVECTION ACROSS
NORTHWEST WI AND THE UP OF MI TO POSE A FLASH FLOOD THREAT DURING
THE EARLY MORNING HOURS.

DISCUSSION...THE CONVECTIVE ACTIVITY THAT PRODUCED FLASH FLOODING
OVER PORTIONS OF NORTHERN AND EASTERN MN AND FAR NORTHWEST WI
CONTINUES TO DROP SOUTHEAST IN WI AND WESTERN UP OF MI. THE MPX
RADAR SHOWED HOURLY RAINFALL RATES BETWEEN 1.50 AND 2.00 INCHES
ACROSS POLK AND BARRON COUNTIES IN WI. 

MEANWHILE...REGIONAL RADARS SHOWED CONVECTION OVER NORTHEAST IA
AND SOUTHEAST MN...AS WELL AS NEW CONVECTION FORMING ON THE NOSE
OF A 40 TO 50 KNOT LOW LEVEL JET...TRACKING INTO NORTHWEST AND
CENTRAL WI. THE KARX AND KMPX RADARS INDICATED THAT THE NEWER
CONVECTION WAS PRODUCING HOURLY RAINFALL RATES BETWEEN 1.00 AND
1.50 INCHES. 

IT NOW APPEARS AS THOUGH THESE TWO AREAS OF CONVECTION WILL MERGE
OVER PORTIONS OF NORTHWEST INTO CENTRAL WI. THE MERGING CELLS
COULD RESULT IN LOCAL 2-3 INCH RAINFALL AMOUNTS ACROSS THESE
AREAS...AND POSSIBLY PORTIONS OF THE WESTERN UP OF MI. THE LATEST
HIGH RESOLUTION GUIDANCE (INCLUDING THE HRRR/PARALLEL HRRR) HAS
BEEN SLOW TO BRING THE AREAS OF CONVECTION TOGETHER INTO NORTHWEST
AND CENTRAL WI. THESE MODELS DO SUPPORT THE ABOVEMENTIONED
RAINFALL AMOUNTS...BUT HAVE BEEN A FEW HOURS SLOW BRINGING THE
ACTIVITY THIS FAR EAST.

ONE HOUR FLASH FLOOD GUIDANCE VALUES ARE AS LOW AS 1.50 INCHES IN
AREAS NOT AFFECTED BY EARLIER RAINFALL. THE MERGER OF THE OLDER
CONVECTION WITH THE NEW CONVECTION COULD RESULT IN LOCAL HOURLY
RAINFALL RATES BETWEEN 1.50 AND 2.00 INCHES...WHICH COULD RESULT
IN FLASH FLOODING. 

HAYES

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

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

LAT...LON   47678816 46438691 45158879 44529067 44859234 
            45909229 47309032