MESOSCALE PRECIPITATION DISCUSSION 0271
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
953 AM EDT FRI JUN 08 2018

AREAS AFFECTED...NORTHEAST IA...FAR SOUTHWEST WI...NORTHERN IL

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

VALID 081350Z - 081800Z

SUMMARY...NUMEROUS SHOWERS AND THUNDERSTORMS WILL FOSTER SOME
FLASH FLOODING CONCERNS THROUGH MIDDAY.

DISCUSSION...THE LATEST GOES-16 CLEAN IR SATELLITE IMAGERY SHOWS A
FAIR DEGREE OF COLD-TOPPED CONVECTION IMPACTING AREAS OF NORTHERN
IA...SOUTHERN MN...SOUTHWEST WI AND NORTHERN IL. THE ACTIVITY IS
BEING FOSTERED BY MULTIPLE SMALL SCALE VORTS THAT ARE ADVANCING
SLOWLY EAST AND INTERACTING WITH A WELL-DEFINED ELEVATED
INSTABILITY GRADIENT FOCUSED NEAR A QUASI-STATIONARY FRONT.

THE LOW LEVEL JET IS CURRENTLY ONLY ON THE ORDER OF 20 TO 25 KTS
OUT OF THE SOUTHWEST...BUT THERE IS SUFFICIENT ISENTROPIC ASCENT
AND DIVERGENT FLOW ALOFT ASSOCIATED WITH THE VORT ENERGY TO
SUSTAIN THE CONVECTION AT LEAST FOR A FEW MORE HOURS. IN
FACT...SOME CLOUD TOP COOLING HAS BEEN NOTED RECENTLY OVER
PORTIONS OF NORTH-CENTRAL IA AND ALSO ACROSS WEST-CENTRAL IL IN
PARTICULAR SUGGESTING RATHER STRONG UPDRAFTS/FORCING.

MEANWHILE...THE PWATS ARE ON THE ORDER OF 1.5 TO 1.6 INCHES AND
THIS IS FOSTERING HEAVY RAINFALL RATES OF AS MUCH AS 2 INCHES/HR
AND ESPECIALLY GIVEN SOME OF THE COLDER AND LOCALLY OVERSHOOTING
TOPS.

THE LATEST HRRR GUIDANCE DOES NOT HAVE A GOOD HANDLE ON THE
CONVECTION ACROSS WEST-CENTRAL/NORTHERN IL IN PARTICULAR...AND MAY
IN GENERAL BE TENDING TO WEAKEN CONVECTION TOO QUICKLY ACROSS THE
BROADER UPPER MIDWEST. THEREFORE...EXPECT SOME ADDITIONAL CONCERNS
FOR HEAVY RAINFALL AT LEAST THROUGH MIDDAY. ADDITIONAL RAINFALL
AMOUNTS OF AS MUCH AS 3 TO 4 INCHES ARE EXPECTED...AND THIS WILL
FOSTER AT LEAST A LOCALIZED FLASH FLOOD THREAT.

ORRISON

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

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

LAT...LON   43519285 43449122 43138984 42788856 42398793
            41838745 41058761 40808828 40768901 40978991
            41309045 41909113 42219190 42589321 42789395
            43319396