MESOSCALE PRECIPITATION DISCUSSION 0378
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 AM EDT FRI JUN 29 2018

AREAS AFFECTED...MUCH OF ND/NORTHWESTERN SD/EXTREME SOUTHEASTERN
MT...

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

VALID 290445Z - 290845Z

SUMMARY...A FAST MOVING MCS WILL CONTINUE TRANSLATING ACROSS THE
STATE OF ND TONIGHT PRODUCING LOCALLY HEAVY RAINFALL. THE PRIMARY
CONCERN SHOULD FOCUS ALONG CELL MERGERS AS DOWNSTREAM ACTIVITY
INTERCEPTS THE QUASI-LINEAR COMPLEX. AN INTENSIFYING NOCTURNAL
LOW-LEVEL JET SHOULD ALLOW THIS CONVECTIVE COMPLEX TO PROSPER WELL
INTO THE OVERNIGHT HOURS WHICH MAINTAINS AN ASSOCIATED FLASH FLOOD
RISK.

DISCUSSION...WSR-88D DOPPLER RADARS SHOW A HEALTHY QUASI-LINEAR
MCS RACING ACROSS WESTERN NORTH DAKOTA WITH OBSERVED EASTWARD
MOTIONS AT NEARLY 45 KNOTS. WHILE SUCH A PROGRESSIVE STORM MODE
WOULD SOMEWHAT MITIGATE A FLASH FLOOD THREAT...IT IS THE ACTIVITY
SPAWNING DOWNSTREAM WHICH REMAINS AN ISSUE...MANY IN THE FORM OF
HIGHLY EFFICIENT SUPERCELLULAR STRUCTURES. WHILE AN ANOMALY...A
3-HOUR TOTAL OF 5.25 INCHES WAS OBSERVED IN DUNN COUNTY WHICH LED
TO FLOODING ISSUES. THE CONVECTIVE COMPLEX IS MOVING INTO THE
CENTRAL SECTIONS OF THE DAKOTAS WHERE AMPLE LOW-LEVEL MOISTURE IS
IN PLACE CHARACTERIZED BY SURFACE DEW POINTS IN THE LOW 70S WITH
MUCAPE VALUES EXCEEDING 4000 J/KG. AIDED BY AN INTENSIFYING
NOCTURNAL LOW-LEVEL JET (40 KNOTS BY 06Z)...SEE LITTLE REASON FOR
THIS CONVECTION TO COLLAPSE ANY TIME SOON.

CONSIDERING THE SURFACE FEATURES IN PLAY...THE BIGGEST CONCERN IS
FOR ANY CONVECTION TO LATCH ONTO THE ANALYZED WEST-SOUTHWEST TO
EAST-NORTHEAST ORIENTED FRONTAL ZONE. THIS HAS ALREADY HAPPENED IN
DUNN COUNTY WHICH LED TO THE IMPRESSIVE 3-HOUR RAINFALL TOTALS.
WHILE THE LATEST CAMS DO NOT SHOW SUCH A SCENARIO UNFOLDING...THEY
HAVE GENERALLY STRUGGLED DEPICTING ANYTHING BEYOND A FORWARD
PROPAGATING MCS. OVERALL...EXPECT HOURLY RAINFALL RATES TO REACH
THE 1 TO 2 INCH MARK WITHIN THE MORE ROBUST CORES AND WITHIN CELL
MERGERS. FLASH FLOODING WILL REMAIN POSSIBLE THROUGH AT LEAST 09Z.

RUBIN-OSTER

ATTN...WFO...ABR...BIS...BYZ...FGF...UNR...

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

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