MESOSCALE PRECIPITATION DISCUSSION 0411
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
538 PM EDT THU JUN 29 2017

AREAS AFFECTED...N IOWA...NE NEBRASKA...SE SOUTH DAKOTA...S
MINNESOTA

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

VALID 292135Z - 300235Z

SUMMARY...HEAVY CONVECTION IS INCREASING IN COVERAGE OVER THIS
REGION IN THE VICINITY OF A STATIONARY FRONT OVER NORTHERN IOWA. 
TRAINING CELLS ARE LIKELY WITH THE POTENTIAL FOR FLASH FLOODING
GIVEN RAINFALL RATES ON THE ORDER OF 1.5 TO PERHAPS 3 INCHES PER
HOUR POSSIBLE.

DISCUSSION...THE LATEST RADAR TRENDS ARE INDICATING BACK-BUILDING
CONVECTION OVER PARTS OF NORTHERN IOWA LATE THIS AFTERNOON, WITH
ADDITIONAL CONVECTION DEVELOPING FARTHER WEST OVER NORTHEAST
NEBRASKA AND SOUTHEAST SOUTH DAKOTA.  EXPANDING AND COOLING CLOUD
TOPS ARE EVIDENT ON IR SATELLITE IMAGERY, AND THIS IS EXPECTED TO
CONTINUE OVER THE NEXT SEVERAL HOURS GIVEN THE APPROACH OF A MID
LEVEL VORTMAX APPROACHING FROM THE WEST ALONG WITH SOME LEFT EXIT
UPPER LEVEL JET DYNAMICS.  PW VALUES NEAR 1.5 INCHES AS PORTRAYED
BY THE RAP MODEL AND STRONGLY CONFLUENT 850MB FLOW AND ENHANCED
MOISTURE CONVERGENCE, ALONG WITH MLCAPES NEAR 2000 J/KG NEAR THE
FRONT, WILL BE ABLE TO SUSTAIN THIS CONVECTION THROUGH THE EARLY
EVENING HOURS.

THE LATEST OPERATIONAL AND EXPERIMENTAL HRRR RUNS APPEAR TO BE
UNDERDONE WITH THE EXPECTED PRECIPITATION AMOUNTS THROUGH 00Z
BASED ON RECENT RADAR TRENDS.  THE ARW AND NMMB ALSO SEEM TOO LOW
WITH THEIR AMOUNTS OVER THIS REGION.  GIVEN THE FAVORABLE
MESOSCALE SET-UP, FLASH FLOODING IS POSSIBLE THROUGH 2Z. 

HAMRICK

ATTN...WFO...ARX...DMX...DVN...FSD...GID...LBF...MPX...OAX...

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

LAT...LON   43769664 43759453 43759286 43639139 42759119
            42029184 41889284 41829446 41789636 41599794
            41789896 42319921 43069891 43609787