MESOSCALE PRECIPITATION DISCUSSION 0435
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
217 AM EDT THU JUL 12 2018

AREAS AFFECTED...NRN MINNESOTA...FAR NW WISCONSIN

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 120616Z - 121200Z

SUMMARY...THUNDERSTORMS WILL CONTINUE TO MOVE ACROSS NORTHERN
MINNESOTA AND WILL LIKELY CONTAIN VERY HEAVY RAIN RATES. SOME OF
THE STORMS MAY REPEATEDLY AFFECT SOME AREAS FROM THE BRAINERD
LAKES REGION EAST TO THE I-35 CORRIDOR AROUND MOOSE LAKE. RAIN
RATES OF 2 IN/HR WILL BE POSSIBLE... WHICH COULD LEAD TO FLASH
FLOODING.

DISCUSSION...RADAR RAINFALL ESTIMATES AND SURFACE OBSERVATIONS
CONTINUE TO SHOW VERY HEAVY RAIN RATES WITH THE THUNDERSTORMS
MOVING ACROSS NORTHERN MINNESOTA. WASHISH (KVWU) REPORTED 1.24
INCHES OF RAIN IN 20 MINUTES AND 1.91 INCHES OF RAIN IN AN HOUR...
AND PARK RAPIDS (KPKD) REPORTED 1.04 INCHES OF RAIN IN 31 MINUTES.
THIS IS CLOSE TO KMVX AND KDLH DUAL POL AND MRMS ESTIMATES OF
POCKETS OF 2 IN/HR RAIN RATES WITH THE STRONGEST CONVECTION. THIS
SHOULD CONTINUE GIVEN PRECIPITABLE WATER VALUES AROUND 2 INCHES
(ABOVE THE 99TH PERCENTILE PER CFSR CLIMATOLOGY)... STRONG
INSTABILITY... AND STRONG LOW-LEVEL INFLOW WHICH WILL FAVOR
ORGANIZED CONVECTION AND HEAVY RAINFALL. THE MOST SIGNIFICANT LINE
OF STORMS STRETCHED FROM GRAND RAPIDS TO BACKUS AT 06Z... AND WAS
SHOWING SIGNS OF FORWARD PROPAGATION... PARTICULARLY ON THE
NORTHERN END. THIS WAS CONTINUING TO LEAD TO GREATER W-E LINE
ORIENTATION. UPSTREAM REDEVELOPMENT OF CONVECTION BEHIND THE
PRIMARY SQUALL LINE... AND ALONG THE TRAILING EDGE... WAS SETTING
UP A FAVORABLE CONFIGURATION FOR INCREASED TRAINING IN THE NEXT
SEVERAL HOURS IN THE BRAINERD LAKES REGION. TO THE NORTH... STORMS
WERE MORE SCATTERED WITH ONE PROMINENT CLUSTER NEAR ORR.

GENERALLY... THIS IS EXPECTED TO CONTINUE WITH MORE SCATTERED
CONVECTION MOVING INTO THE MINNESOTA AREA... AND A MORE FOCUSED
BAND OF CONVECTION ON THE EDGE OF THE CAP (ROUGHLY OUTLINED BY THE
+12C ISOTHERM AT 700MB). AS THE LARGER LINE OF STORMS CONTINUES TO
INTERCEPT LOW-LEVEL INFLOW... THAT SHOULD INCREASINGLY BE THE
FOCUS AREA FOR HEAVY RAINFALL. 925-850MB FLOW WILL ALSO VEER OVER
THE NEXT SEVERAL HOURS... LEADING TO MORE LINE-PARALLEL FLOW AND
FAVORING NEW UPDRAFT FORMATION JUST WSW-W OF AN INCREASINGLY W-E
ORIENTED LINE. AGAIN... THIS WILL FAVOR MORE TRAINING AND AN
INCREASED THREAT OF FLASH FLOODING BETWEEN 06Z AND 12Z IN
NORTH-CENTRAL MINNESOTA.

IT SEEMS AT LEAST CONCEIVABLE THAT 1-2 IN/HR RAIN RATES COULD BE
SUSTAINED AT A GIVEN LOCATION FOR A COUPLE HOURS... AND LOCALIZED
RAINFALL TOTALS AROUND OR JUST OVER 5 INCHES WOULD NOT BE OUT OF
THE QUESTION. VALUES THAT HIGH HAVE AN ANNUAL EXCEEDANCE
PROBABILITY OF LESS THAN 2 PERCENT BASED ON THE CLIMATOLOGY AT
BRAINERD MN...AND WOULD BE LIKELY TO LEAD TO FLOODING ISSUES WERE
THEY TO OCCUR.

LAMERS

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

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

LAT...LON   48379128 48158966 47388972 46339076 45899193
            45809300 46049461 46759596 47839421 48279285