MESOSCALE PRECIPITATION DISCUSSION 0334
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
417 AM EDT WED JUN 20 2018

AREAS AFFECTED...FAR NORTHEAST WY...WESTERN SD

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

VALID 200815Z - 201415Z

SUMMARY...PERSISTENT HEAVY RAINFALL MAY RESULT IN SOME FLASH
FLOODING CONCERNS THROUGH MID-MORNING.

DISCUSSION...THE LATEST RADAR IMAGERY IS SHOWING A VERY PERSISTENT
AXIS OF HEAVY RAINFALL IMPACTING AREAS OF WESTERN SD AND NORTHEAST
WY WITH A FOCUS ON THE BLACK HILLS.

THE ACTIVITY IS BEING HIGHLY FORCED BY A COMPACT MID LEVEL LOW
CENTER OVER SOUTHWEST SD...WHICH IS FOSTERING A STRONG DEFORMATION
ZONE OVER THE REGION AND IS WORKING TANDEM WITH A FOCUSED AREA OF
LOW LEVEL MOISTURE CONVERGENCE. INSTABILITY IS QUITE WEAK WITH
MUCAPE VALUES OF ABOUT 250 J/KG...BUT THE HIGHLY DYNAMICAL
ENVIRONMENT IS COMPENSATING FOR PERSISTENT HEAVY RAINFALL ALONG
WITH EMBEDDED THUNDERSTORMS.

THE LATEST HIRES MODEL CONSENSUS SUPPORTS AS MUCH AS AN ADDITIONAL
2 TO 3 INCHES OF RAIN GOING THROUGH MID-MORNING. THE HOURLY RATES
WITH SOME OF THE STRONGER CONVECTIVE ELEMENTS MAY EXCEED 1 INCH/HR
WHICH WOULD ACTUALLY EXCEED FFG VALUES. BASED ON THIS AND THE
ADDITIONAL STORM TOTALS THIS MORNING...SOME FLASH FLOODING WILL BE
POSSIBLE.

ORRISON

ATTN...WFO...BYZ...UNR...

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

LAT...LON   45360311 44950248 44360213 44040211 43920231
            43850246 43750271 43240302 43280366 43550407
            43920439 44220451 44850449 45340390