MESOSCALE PRECIPITATION DISCUSSION 454
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
645 PM EDT TUE AUG 18 2015
 
AREAS AFFECTED...CENTRAL WI...NORTHERN IL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 182244Z - 190214Z
 
SUMMARY...SATELLITE AND RADAR TRENDS SHOW AN INCREASE IN
CONVECTIVE ACTIVITY ACROSS SOUTHERN WISCONSIN AND INTO CENTRAL
ILLINOIS.  MULTIPLE ROUNDS OF CONVECTION ARE LIKELY AHEAD OF A
STRONG MID-LATITUDE SURFACE LOW.

DISCUSSION...A DEVELOPING SQUALL LINE EVIDENT ON THE LATEST RADAR
IMAGERY IS FORECAST TO MOVE THROUGH EASTERN WISCONSIN AND
NORTHEAST ILLINOIS THROUGH 9 PM LOCAL TIME.  ALTHOUGH THIS SWATH
OF HEAVY CONVECTION IS RATHER PROGRESSIVE, MULTIPLE ROUNDS OF
THUNDERSTORMS ARE POSSIBLE AND MAY BE ENOUGH FOR A MARGINAL SHORT
TERM FLASH FLOODING THREAT IN LOCALIZED AREAS.  PRECIPITABLE WATER
VALUES OF 1.5-2.0" ARE PRESENT OVER THIS REGION, ALONG WITH MLCAPE
ON THE ORDER OF 1000 TO 2000 J/KG PER THE LATEST SPC MESOSCALE
ANALYSIS, WHICH IS SUFFICIENT WITHIN THIS MOIST ENVIRONMENT.

WITH RESPECT TO MODEL GUIDANCE, THE 21Z HRRR IS SUGGESTING 3-HOUR
RAINFALL AMOUNTS APPROACHING 3 INCHES FROM SOUTHERN WISCONSIN TO
NORTHEAST ILLINOIS BY 8 PM.  THE LATEST HRW AND SPC WRF ALSO
SUPPORT SCATTERED 2 AND 3 INCH AMOUNTS OVER THE SAME GENERAL AREA.
 THE MAJORITY OF THE MODEL GUIDANCE SUPPORT A LOW-END FLOODING
THREAT THAT IS NOT EXPECTED TO BE WIDESPREAD.  HOWEVER, THE
ANOMALOUS STRENGTH OF THE OVERALL STORM SYSTEM SHOULD BE ABLE TO
TAKE ADVANATGE OF THE CAPE AND HIGH PW VALUES PRESENT.

HAMRICK

ATTN...WFO...ARX...DVN...GRB...ILX...LOT...MKX...MQT...

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

LAT...LON   45438878 45258766 44768720 44058716 42828723 
            41678727 40778749 40188825 40238972 41379013 
            42619020 44389025 45208977