MESOSCALE PRECIPITATION DISCUSSION 0323
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1014 PM EDT MON JUN 18 2018

AREAS AFFECTED...CENTRAL/EASTERN IA...SOUTHWEST WI...NORTHERN IL

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

VALID 190210Z - 190810Z

SUMMARY...THE THREAT FOR ADDITIONAL FLASH FLOODING CONTINUES AS
MORE HEAVY SHOWERS AND THUNDERSTORMS DEVELOP OVER THE REGION.

DISCUSSION...THE LATEST RADAR IMAGERY SHOWS MULTIPLE CLUSTERS OF
HEAVY SHOWERS AND THUNDERSTORMS DEVELOPING ALONG AND A VERY
SLOW-MOVING FRONT DRAPED FROM CENTRAL IA EAST ALONG THE IL/WI
BORDER. THE CONVECTION IN PART HAS BEEN FOCUSING ALONG THE FRONT
WITH THE AID OF AN AREA OF LOW PRESSURE OVER FAR EASTERN IA AND
ALSO LARGER SCALE UPPER DIVERGENCE AHEAD OF A SHORTWAVE TROUGH
EXITING THE CENTRAL PLAINS. THE SURFACE WAVE AND ENERGY ALOFT IS
INTERACTING WITH A WELL-DEFINED INSTABILITY GRADIENT WITH MLCAPE
VALUES NOTED AS HIGH AS 1500 J/KG FROM CENTRAL IA EAST ACROSS
NORTHWEST IL.

PWATS ACROSS THE REGION ARE VERY HIGH...WITH VALUES GENERALLY
BETWEEN 2.0 AND 2.2 INCHES...AND THIS IS FOSTERING VERY HEAVY
RAINFALL RATES GIVEN HIGHLY EFFICIENT RAINFALL PROCESSES. GIVEN
THE CONTINUATION OF COLD CONVECTIVE TOPS...SOME ADDITIONAL
RAINFALL RATES OF AS MUCH AS 2.5 INCHES/HR CAN BE EXPECTED.

THE UPSTREAM SHORTWAVE WILL BE CROSSING THE MIDWEST TONIGHT...AND
WITH AT LEAST MODEST SOUTHWEST LOW LEVEL FLOW AHEAD OF IT...AND
INTERACTION WITH THE FRONT...THERE WILL CONTINUE TO BE CLUSTERS OF
HEAVY SHOWERS AND THUNDERSTORMS.

THE LATEST HRRR/HRRRX GUIDANCE AGREES WITH THIS SCENARIO AND
SUPPORTS AS MUCH AS ANOTHER 3 TO 4 INCHES OF RAIN WITH LOCALLY
HEAVIER TOTALS. FLASH FLOODING IS ONGOING RIGHT NOW ACROSS
NORTHWEST IL...ESPECIALLY AROUND THE ROCKFORD IL AREA...AND
ADDITIONAL FLASH FLOODING IS LIKELY. THE THREAT ALSO CONTINUES
UPSTREAM ACROSS CENTRAL AND EASTERN IA. WILL CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   43279137 43259019 42928880 42578782 41998749
            41478765 41218855 41358967 41529068 41449225
            41559296 42099337 42789303 43089238