MESOSCALE PRECIPITATION DISCUSSION 0365
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
928 AM EDT THU JUN 22 2017

AREAS AFFECTED...NORTHERN IA...SOUTHWEST WI

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

VALID 221325Z - 221830Z

SUMMARY...STRONG THUNDERSTORMS WITH HEAVY RAIN WILL LIKELY
CONTINUE TO BE A THREAT OVER THE NEXT SEVERAL HOURS. SOME FLASH
FLOODING WILL BE POSSIBLE.

DISCUSSION...THE LATEST EXPERIMENTAL GOES-16 MICRON/IR IMAGERY
SHOWS A RATHER LARGE AREA OF COOLING CONVECTIVE TOPS OVER NORTHERN
IA IN ASSOCIATION WITH AN AXIS OF STRONG THUNDERSTORMS THAT HAVE
BEEN BECOMING BETTER ORGANIZED OVER THE LAST COUPLE OF HOURS. THE
CONVECTION IS DEVELOPING WITHIN A WELL-DEFINED WARM ADVECTION
PATTERN INTERACTING WITH A SURFACE OUTFLOW/MESOSCALE
BOUNDARY...AND BEING AIDED BY A SOUTHWEST LOW LEVEL JET OF 40 TO
45 KTS. ALL OF THIS IS DEVELOPING AHEAD OF A COLD FRONT MEANWHILE
THAT IS ALSO DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST.

THE CONVECTION IS IN A FAIRLY UNSTABLE AND MOIST ENVIRONMENT WITH
MUCAPE VALUES OF 1500 TO 2000 J/KG AND PWATS OF 1.5 TO 1.7 INCHES
WHICH IS FACILITATING RAINFALL RATES OF 1.5 TO 2 INCHES/HR
LOCALLY. OVER THE NEXT FEW HOURS...THE CONVECTION MAY BE ABLE TO
PERSIST AND SUSTAIN ITSELF AS THE LOW LEVEL JET PERSISTS AHEAD OF
THE APPROACHING COLD FRONT...AND WITH A CONTINUED POOLING OF
DEEPER MOISTURE/INSTABILITY ALONG THE FRONT. THE INTERACTION OF
THIS WITH THE CONVECTIVELY REINFORCED OUTFLOW BOUNDARY SUGGESTS AN
ENVIRONMENT CONDUCIVE FOR SOME BACKBUILDING/TRAINING CONVECTION.
SEPARATE CONVECTIVE CLUSTERS UPSTREAM WITH THE ACTUAL COLD FRONT
MAY ALSO DEVELOP AND IMPACT THE REGION LATER THIS MORNING OR THIS
AFTERNOON.

HIRES MODEL OUTPUT HAS BEEN HANDLING THE CURRENT ACTIVITY VERY
POORLY WITH LITTLE ORGANIZED CONVECTIVE SIGNAL...BUT WITH
RADAR/SATELLITE TRENDS SUGGESTING OTHERWISE...IT APPEARS THAT
LOCALLY SEVERAL INCHES OF RAIN MAY RESULT. EXPECT LOCALLY AS MUCH
AS AN ADDITIONAL 2 TO 4 INCHES THROUGH 18Z...WITH ISOLATED HEAVIER
TOTALS NOT OUT OF THE QUESTION FOR ESPECIALLY AREAS OF NORTHEAST
IA. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...ARX...DMX...DVN...MKX...MPX...

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

LAT...LON   43539297 43489121 43269011 42599005 42339068
            42339225 42479361 42769425 43169454 43459409