MESOSCALE PRECIPITATION DISCUSSION 0321
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
514 PM EDT MON JUN 18 2018

AREAS AFFECTED...EASTERN NE...CENTRAL IA...NORTHWEST
IL...SOUTHWEST WI

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

VALID 182114Z - 190214Z

SUMMARY...A VERY HUMID ENVIRONMENT AND MULTIPLE ROUNDS OF SLOW
MOVING THUNDERSTORM CELLS INCREASE THE FLASH FLOODING RISK THROUGH
THE EVENING HOURS FROM EASTERN NEBRASKA TO THE GREATER CHICAGO
AREA.

DISCUSSION...A QUASI-STATIONARY FRONTAL ZONE SITUATED FROM CENTRAL
NEBRASKA TO SOUTHERN WISCONSIN IS INTERCEPTING A VERY MOIST LOWER
TROPOSPHERIC FLOW.  ENHANCED MOISTURE CONVERGENCE IN THE PRESENCE
OF PWS AT OR SLIGHTLY ABOVE 2 INCHES, ALONG WITH LOW LEVEL FLOW
NEARLY PARALLEL TO THE FRONT, IS RESULTING IN MULTIPLE ROUNDS OF
THUNDERSTORMS WITH VERY HEAVY RAIN THAT WILL CONTINUE TO GROW IN
COVERAGE THROUGH 00Z THIS EVENING.  MLCAPE OF 2000 TO 3000 J/KG
WILL SUPPORT VIGOROUS UPDRAFTS CAPABLE OF PRODUCING HEAVY RAINFALL
RATES IN EXCESS OF 2 INCHES PER HOUR AT TIMES.  ASCENT IS ALSO
AIDED BY A MODEST 500MB VORTMAX OVER NEBRASKA AND RIGHT ENTRANCE
JET DYNAMICS.

THE LATEST HIGH RES GUIDANCE IS INDICATING THE POTENTIAL FOR 2 TO
4 INCHES OF RAINFALL IN SCATTERED PATCHES WHERE THESE STORMS ARE
ABLE TO TRAIN OVER THE SAME AREAS.  THE BEST SIGNAL FOR THE QPF
MAXIMA IS ALONG AND JUST NORTH OF THE INTERSTATE 80 CORRIDOR. 
FLASH FLOODING IS MOST LIKELY IN THOSE AREAS THAT RECEIVE 2 INCHES
OF RAIN WITHIN 3 HOURS BASED ON THE LATEST FLASH FLOOD GUIDANCE.

D. HAMRICK

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

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

LAT...LON   43349060 43338932 43048835 42558795 42078823
            41738904 41499064 41439241 41389375 41209481
            40829610 40999703 41469738 42239706 42769627
            43089520 43249432 43339228