MESOSCALE PRECIPITATION DISCUSSION 0458
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1055 PM EDT SUN JUL 09 2017

AREAS AFFECTED...CENTRAL/SOUTHEAST MN...NORTHEAST IA...FAR WESTERN
WI

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

VALID 100255Z - 100755Z

SUMMARY...STRONG SUPERCELL THUNDERSTORMS EXPANDING OVER PARTS OF
CENTRAL/SOUTHEAST MN WILL LIKELY ORGANIZE INTO CLUSTERS OF
CELL-MERGERS WITH INTENSE RAINFALL RATES AS
MCS DEVELOPMENT COMMENCES.

DISCUSSION...SEVERE MODE CONVECTION CONTINUES TO DEVELOP AND
EXPAND IN COVERAGE ACROSS CENTRAL/SOUTHEAST MN THIS EVENING AS A
RATHER STRONG SHORTWAVE DROPS SOUTHEAST ALONG WITH AN AREA OF LOW
PRESSURE INTO A RATHER STRONGLY UNSTABLE AND HIGHLY SHEARED
ENVIRONMENT. AS PER SPC MCD #1271...MLCAPE VALUES ARE WELL IN
EXCESS OF 2000 J/KG AND WITH OVER 50 KTS OF EFFECTIVE BULK SHEAR.
THE CONVECTION IS GENERALLY FOCUSING ALONG AND NORTH OF A WARM
FRONT AND BEING AIDED BY A SOUTHWEST LOW LEVEL JET OF 30 TO 40
KTS. THIS NOCTURNALLY ENHANCED LOW LEVEL JET SHOULD INCREASE TO
NEAR 50 KTS TOWARD 06Z...AND WITH STRONGER MOISTURE
TRANSPORT...THE RAINFALL RATES WILL BECOME MORE INTENSE AS PWATS
RISE TO NEAR 1.75 INCHES.

THE CONVECTION WILL TEND TO BE QUITE PROGRESSIVE OVERALL AS
GRADUALLY THE CLUSTERS OF THUNDERSTORMS WILL MERGE AND EVOLVE INTO
A FORWARD PROPAGATING MCS. HEAVY RAINFALL AMOUNTS OF AS MUCH AS 3
TO 4 INCHES WITH ISOLATED HEAVIER AMOUNTS WILL BE POSSIBLE...BUT
THIS WILL MAINLY BE ASSOCIATED WITH WHERE THE STRONGER CONVECTIVE
CORES SET UP AND WHERE CELL-MERGER ACTIVITY TAKES PLACE. SOME
SMALL SCALE CELL-TRAINING IS POSSIBLE AS WELL. THUS...EXPECT SOME
LOCALIZED RUNOFF AND/OR FLASH FLOODING CONCERNS OVER THE NEXT
SEVERAL HOURS AS THIS CONVECTIVE COMPLEX TAKES SHAPE AND DROPS
SOUTHEAST THROUGH SOUTHEAST MN...AND GRADUALLY AREAS OF NORTHEAST
IA AND PARTS OF FAR WESTERN WI TOWARD AND AFTER 06Z.

ORRISON

ATTN...WFO...ARX...DMX...DVN...FSD...MKX...MPX...

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

LAT...LON   45699300 44369083 43109014 42119052 41829143
            41909301 42509442 43369545 44259584 45019581
            45589486