MESOSCALE PRECIPITATION DISCUSSION 0277
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
440 PM EDT SAT JUN 09 2018

AREAS AFFECTED...SOUTH-CENTRAL TO SOUTHEAST MN...NORTH-CENTRAL TO
NORTHEAST IA...WEST-CENTRAL TO SOUTHWEST WI...NORTHWEST IL

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 092040Z - 100240Z

SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
REDEVELOP AND EXPAND SIGNIFICANTLY IN COVERAGE LATE THIS AFTERNOON
AND EVENING. VERY INTENSE RAINFALL RATES TO NEAR 3 INCHES/HR AND
WET ANTECEDENT CONDITIONS WILL MAKE FLASH FLOODING LIKELY.

DISCUSSION...THE LATEST GOES-16 VISIBLE SATELLITE IMAGERY SHOWS A
STRONG MCV ADVANCING EAST ACROSS SOUTH-CENTRAL MN WITH THE
RGB-AIRMASS IMAGERY SUGGESTING A WELL-DEFINED PV ANOMALY
ASSOCIATED WITH IT.

THIS ENERGY IS EXPECTED TO INTERACT QUITE AGGRESSIVELY OVER THE
NEXT 2 TO 3 HOURS WITH A STRONG INSTABILITY AXIS POOLED NORTH UP
ACROSS CENTRAL AND EASTERN IA WHERE IN SOME CASES MUCAPE VALUES
ARE WELL OVER 3000 J/KG. THERE REMAINS SOME LOW LEVEL CINH OVER
NORTHEAST IA...BUT STRONG SURFACE HEATING WILL OVERCOME THIS AND
ALLOW CONVECTIVE INITIATION TO TAKE PLACE VERY SOON.

THIS WILL BE FACILITATED BY ENHANCING LOW LEVEL CONVERGENCE ALONG
AND NORTH OF A WARM FRONT AHEAD OF THE SURFACE WAVE OVER
NORTH-CENTRAL IA AND FAVORABLE DEEP LAYER SHEAR OF 35 TO 45 KTS.
THE MODE OF CONVECTION WILL LIKELY BE SUPERCELLULAR AS
ORGANIZATION BEGINS...BUT UPSCALE GROWTH INTO A STRONG MCS IS
EXPECTED THIS EVENING AS MERGING SUPERCELLS EVOLVE NEAR AND TO THE
NORTHEAST OF THE FRONT AND EVENTUAL TRACK DOWN TO THE SOUTHEAST
PARALLEL TO THE BOUNDARY.

THE MODELS ARE INSISTENT OVER VERY HEAVY RAINFALL DEVELOPING LATE
THIS AFTERNOON AND EVENING ACROSS AREAS OF ESPECIALLY SOUTHEAST
MN...NORTHEAST IA AND POTENTIALLY GETTING INTO
WEST-CENTRAL/SOUTHWEST WI BY LATE EVENING. ASSUMING STRONGER
CONVECTIVE ORGANIZATION THAN WHAT THE ARW/NMMB AND HRRR/HRRRX
GUIDANCE ARE SUGGESTING...IT IS NOT OUT OF THE QUESTION THAT FAR
NORTHWEST IL WILL NEED TO BE MONITORED BY LATE EVENING AS WELL.

PWATS ARE ALREADY UP NEAR 1.5 INCHES ACROSS THE REGION...AND WITH
VERY COLD CONVECTIVE TOPS/FORCING EXPECTED INCLUDING OVERSHOOTING
TOPS...THE RAINFALL RATES COULD EASILY APPROACH 3 INCHES/HR. THIS
WILL EASILY EXCEED FFG VALUES ACROSS MOST OF THE THREAT AREA.
RAINFALL TOTALS OF AS MUCH AS 3 TO 5 INCHES ARE EXPECTED...WITH
ISOLATED HEAVIER AMOUNTS THROUGH 03Z.

GIVEN THE WET ANTECEDENT CONDITIONS AND THE EXPECTED RAINFALL
RATES AND CORRELATING STORM TOTALS...FLASH FLOODING WILL BE LIKELY.

ORRISON

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

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

LAT...LON   44599291 44539181 44049073 43469016 42608966
            41878967 41429024 41499141 41719217 42089264
            42509310 42949361 43239411 43909422 44349378