MESOSCALE PRECIPITATION DISCUSSION 0515
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1230 AM EDT THU JUL 20 2017

AREAS AFFECTED...SERN MN/CNTRL-SRN WI/FAR NERN IA

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

VALID 200429Z - 200930Z

SUMMARY...RAINFALL RATES OF 1-2 IN/HR ARE EXPECTED TO CONTINUE
ACROSS PORTIONS OF SERN MN INTO CNTRL-SRN WI THROUGH 08Z. FLASH
FLOODING WILL BE POSSIBLE...ESPECIALLY OVER WET GROUND FROM
EARLIER RAINFALL.

DISCUSSION...AN AXIS OF SEMI-CONTINUOUS TRAINING CONVECTION HAS
BEEN IN PLACE FROM JUST SOUTH OF MSP TO JUST NORTH OF LSE SINCE
ABOUT 02Z. OBSERVED RAINFALL RATES WITHIN THIS AXIS HAVE RANGED
FROM 1-2 IN/HR WHERE IDEAL TRAINING HAS SET UP. THE CONVECTION IS
OCCURRING NORTH OF A WARM FRONT STRETCHING FROM FAR SWRN MN INTO
SERN IA AND APPEARS TO BE ROOTED NEAR OR BELOW 700 MB PER THE 00Z
MPX SOUNDING. THE CONVECTION ALSO APPEARS TO BE OCCURRING NEAR THE
EDGE OF AN INSTABILITY GRADIENT WITH THE 00Z MPX SOUNDING
INDICATING INSTABILITY OF ABOUT 100 J/KG BUT IT WAS CLOSER TO 1800
J/KG TO THE SOUTH AT DVN FROM 00Z. MID-UPPER LEVEL FLOW WAS ALSO
FAIRLY DIFFLUENT OVER THE AREA OF ONGOING CONVECTION.

MODERATE WLY-SWLY FLOW IN THE 850-700 MB LAYER IS HELPING TO PUMP
INSTABILITY INTO THE REGION AND WILL LIKELY CONTINUE TO DO SO OVER
THE NEXT FEW HOURS. GIVEN GPS SITE PRECIPITABLE WATER VALUES OVER
THE TRI-STATE AREA RANGED FROM 1.5 TO 1.9 INCHES AT 02Z...AND
THERE SHOULD BE NO SHORTAGE OF INSTABILITY IN THE SOURCE
REGION...RAINFALL RATES OF 1-2 IN/HR WILL CONTINUE TO BE SEEN
WHERE TRAINING CONTINUES WITHIN UNIDIRECTIONAL FLOW FROM NW TO SE
WITHIN THE EFFECTIVE SHEAR LAYER. RAINFALL FROM AN EARLIER MCS
PRODUCED 1-2 INCHES OF RAIN IN AREAS FROM SERN MN INTO SWRN
WI...AND ADDITIONAL RAINFALL OF 2-4 INCHES MAY CAUSE FLASH
FLOODING IN A FEW LOCATIONS.

OTTO

ATTN...WFO...ARX...GRB...MKX...MPX...

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

LAT...LON   45189148 44258895 42938858 42628962 42769050
            43249150 44069386 45129365