MESOSCALE PRECIPITATION DISCUSSION 0317
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1053 PM EDT SUN JUN 17 2018

AREAS AFFECTED...SOUTHEAST SD...SOUTHERN MN...WESTERN AND CENTRAL
WI

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

VALID 180252Z - 180800Z

SUMMARY...RADAR AND SATELLITE IMAGERY WAS SHOWING ADDITIONAL
CONVECTION DEVELOPING OVER FAR NORTHEAST NE AND SOUTHEAST SD.  THE
CONVECTION WAS ORIENTED NORTHEAST TO SOUTHWEST WHICH WAS ALSO THE
AXIS OF CONVECTION.  AS A RESULT...TRAINING OF CELLS AND REPEAT
CONVECTION MAY RESULT IN FLASH FLOODING WHERE STORMS TRAIN AND
EXPAND IN AREAL COVERAGE OVERNIGHT.

DISCUSSION...THUNDERSTORMS WERE DEVELOPING OVER SOUTHEAST SD AND
NORTHEAST NE AS OF 02Z IN RESPONSE TO THE APPROACH OF A MID LEVEL
IMPULSE.  THIS SHOULD LEAD TO THE GENERATION OF THUNDERSTORMS
CAPABLE OF PRODUCING HEAVY RAINFALL LATER TONIGHT.

THE 00Z AND 01Z RUNS OF BOTH THE HRRR AND EXPERIMENTAL HRRR HAVE
STARTED TO DEPICT AREAS OF 1 TO 2 INCH AMOUNTS SPREADING FROM
SOUTHEAST SD INTO SOUTHERN MN AND SOUTHWEST WI THROUGH 08Z.  THE
RAP SHOWED THE AXIS OF BEST SURFACE MOISTURE FLUX CONVERGENCE
ALONG THIS AREA ALONG WITH MIXED LAYER CAPES AROUND 1000 J PER KG
PERSISTING BEYOND MIDNIGHT CDT.  THUS CONFIDENCE IS BUILDING THAT
THE SD CONVECTION SHOULD MAKES ITS WAY NORTHEAST.  RAINFALL RATES
OF 1 TO 2 INCHES PER HOUR ARE EXPECTED WITH MOST ACTIVE
CONVECTION.  FLASH FLOOD GUIDANCE WAS GENERALLY 1.5 INCHES PER
HOUR...ALTHOUGH AREAS OF FFG AS LOW AS 1 INCH PER HOUR WERE
SCATTERED ACROSS SOUTHERN MN. AS A RESULT...FLASH FLOODING IS
POSSIBLE.

ACROSS THE EASTERN PART OF THE AREA...CELLS PRODUCING HEAVY
RAINFALL HAD LEFT BETWEEN 3 AND 4 INCHES IN PLACES ALREADY THIS
EVENING OVER PORTIONS OF WESTERN WI.  THINKING IS THAT THE
RAINFALL RATES HAVE STARTED TO WEAKEN AND WILL CONTINUE TO DO SO
BASED ON GOES SATELLITE IMAGERY. IN ADDITION...HEAVY RAIN WITHIN
THIS AREA SHOULD BE SHIFTING EASTWARD LEAVING A RESPITE BEFORE ANY
NEW HEAVY RAINFALL BUILDS IN FROM THE WEST LATER.  ANY RAINFALL
HERE WILL EXACERBATE ANY ON GOING FLOODING AND OPEN THE
POSSIBILITY OF ADDITIONAL FLASH FLOODING ELSEWHERE.

BANN

ATTN...WFO...ARX...DMX...FSD...GRB...MPX...OAX...

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

LAT...LON   45009048 44158923 42589462 42029715 43019747
            44459268