MESOSCALE PRECIPITATION DISCUSSION 0379
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
328 PM EDT SAT JUN 30 2018

AREAS AFFECTED...ERN NE...IA...SRN MN...WRN WI

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

VALID 301926Z - 010100Z

SUMMARY...RAPID DEVELOPMENT OF CONVECTION IS EXPECTED TO POSE A
THREAT OF FLASH FLOODING THROUGH THE REMAINDER OF THE AFTERNOON
FROM EASTERN NEBRASKA INTO IOWA...SOUTHERN MINNESOTA AND WESTERN
WISCONSIN. RAINFALL RATES OF 2-3 IN/HR WILL BE POSSIBLE WHERE CELL
TRAINING OCCURS.

DISCUSSION...18Z SURFACE OBSERVATIONS PLACED A SLOW MOVING COLD
FRONT SOUTHWESTWARD FROM NORTHERN WISCONSIN INTO WEST-CENTRAL IOWA
AND SOUTHEASTERN NEBRASKA. SPECIAL 18Z RAOBS SHOWED PRECIPITABLE
WATER VALUES RANGING FROM 1.3 INCHES AT MPX TO 1.7 INCHES AT OAX
WITH THE LAYERED PRECIPITABLE WATER PRODUCT INDICATING DEEP
LAYERED MOISTURE STREAMING NORTHEASTWARD FROM WEST TEXAS INTO THE
CENTRAL PLAINS AND UPPER MIDWEST. THE 18Z SPC MESOANALYSIS AGREED
WITH THE 18Z OAX SOUNDING SHOWING MODERATE TO HIGH MLCAPE VALUES
RANGING FROM 2500 TO 3500+ J/KG AHEAD OF THE FRONT WITH ERODING
CIN.

CONVECTION FROM 19Z WAS LOCATED IN NORTH-CENTRAL IOWA WHERE MEAN
CELL MOTIONS WERE OFF TOWARD THE NORTHEAST AT AROUND 20 KT. VAD
WIND PLOTS INDICATED A REGION OF RELATIVELY STRONGER 850 MB WINDS
OUT AHEAD OF THE SURFACE FRONT RANGING BETWEEN 15-20 KT FROM THE
SOUTHWEST...WHICH WOULD PROMOTE SOME BACKBUILDING AND TRAINING OF
CONVECTION. THIS IS ALREADY BEGINNING JUST WEST OF I-35 IN
NORTHERN IOWA AND ADDITIONAL CELLS ARE EXPECTED TO DEVELOP INTO
SOUTHEASTERN MINNESOTA AND WESTERN WISCONSIN WITHIN THE NEXT 2-3
HOURS AS THIS IS A REGION WHERE CIN IS ESTIMATED TO BE LOWEST AND
THE SPECIAL 18Z SOUNDING FROM OAX INDICATED 27 J/KG CIN REMAINING.

WHILE CONVECTION HAS STRUGGLED TO DEVELOP ACROSS EASTERN NEBRASKA
AS OF 19Z...RECENT RUNS OF THE HRRR AND EXPERIMENTAL HRRR ARE IN
GOOD AGREEMENT WITH DEVELOPMENT OCCURRING NEAR 21Z. BEYOND
21Z...850 MB FLOW IS FORECAST TO INCREASE INTO THE 25-35 KT RANGE
WHICH WOULD HELP TO SUPPORT TRAINING GIVEN MEAN FLOW PARALLEL TO
THE SURFACE BOUNDARY. IN ADDITION...INCREASED FORCING AHEAD OF AN
MCV...CURRENTLY OVER CENTRAL KS...MAY HELP WITH CONVECTIVE
DEVELOPMENT INTO NEBRASKA TOWARD 00Z.

GIVEN LOW FLASH FLOOD GUIDANCE FROM RECENT HEAVY RAINFALL...FLASH
FLOODING IS CONSIDERED LIKELY. 6 HOUR RAINFALL MAXIMA OF 3-5
INCHES ARE EXPECTED THROUGH 01Z ACROSS THE MPD THREAT AREA.

OTTO

ATTN...WFO...ARX...DLH...DMX...DVN...EAX...FSD...GID...GRB...
MPX...OAX...

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

LAT...LON   45499085 45129014 44229034 42819113 41659252
            40999373 40379587 40029737 40199794 40709827
            41429733 42389587 43299395 44699217