MESOSCALE PRECIPITATION DISCUSSION 0373
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1047 PM EDT THU JUN 22 2017

AREAS AFFECTED...EASTERN IA & SOUTHWEST WI

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

VALID 230245Z - 230645Z

SUMMARY...THUNDERSTORMS ARE INCREASING IN COVERAGE OVER AN AREA
WITH PARTIALLY SATURATED SOILS.  HOURLY RAIN RATES TO 2" WITH
LOCAL AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...THUNDERSTORMS ARE BLOSSOMING ACROSS NORTHEAST IA
AHEAD OF A FRONTAL WAVE.  THIS IS OCCURRING TO THE SOUTH OF AN
UPPER LOW LOCATED ACROSS SOUTHEAST MANITOBA, WHICH AIDED
DIVERGENCE ALOFT.  PRECIPITABLE WATER VALUES ARE 1.5-1.75" PER
RECENT GPS VALUES.  INFLOW AT 850 HPA IS 15-25 KTS PER VAD WIND
PROFILES, NEAR THE MAGNITUDE OF THE MEAN 850-400 HPA WIND. 
EFFECTIVE BULK SHEAR IS NEAR 40 KTS, WHICH APPEARS TO BE LEADING
TO THE FORMATION OF MESOCYCLONES WHICH ARE ENHANCING RAIN RATES.

INCREASING CELL COVERAGE IS EXPECTED OVER THE SHORT TERM. 
PROGRESSION IS EXPECTED AS THE FRONTAL ZONE SAGS SOUTHEAST, MOVING
THE FRONTAL WAVE EASTWARD WITH TIME.  INITIALLY STORMS HAVE BEEN
MOVING EAST TO EAST-NORTHEAST AT ~25 KTS WITH THE FORWARD
PROPAGATING CONVECTIVE VECTORS.  HOWEVER, CELL COVERAGE SHOULD EAT
AWAY AS AVAILABLE INSTABILITY AND ALLOW STORMS WITH HEAVIER RAIN
RATES TO DROP EAST-SOUTHEAST PARALLEL TO THE 1000-500 HPA
THICKNESS PATTERN.  THE 12Z SPC WRF AND 00Z HRRR RUNS APPEAR TO
HAVE CAPTURED THE AREA OF IMPACT THE PAST OVER THE NEXT FOUR
HOURS.  HOURLY RAIN RATES UP TO 2", WITH LOCAL AMOUNTS TO 4", ARE
EXPECTED.  FLASH FLOODING IS A CONCERN SINCE 3-7" OF RAIN HAS
FALLEN ACROSS PORTIONS OF THIS AREA OVER THE PAST 42 HOURS, WHICH
HAS PARTIALLY SATURATED SOILS.

ROTH

ATTN...WFO...ARX...DMX...DVN...LOT...MKX...

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

LAT...LON   43659010 42648882 41738988 41429173 41549333
            42059429 42839403 43579238