MESOSCALE PRECIPITATION DISCUSSION 0254
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
343 PM EDT FRI JUN 01 2018

AREAS AFFECTED...WESTERN AND CENTRAL ND

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

VALID 011942Z - 020100Z

SUMMARY...TRAINING OF CONVECTION IS POSSIBLE INTO EARLY EVENING,
WITH LOCALIZED RAINFALL AMOUNTS OF 2-3 INCHES. FLASH FLOODING IS
POSSIBLE.

DISCUSSION...A VERY WARM, MOIST, AND HIGHLY UNSTABLE AIR MASS IS
IN PLACE SOUTH OF A WARM FRONT ACROSS SOUTH DAKOTA AS OF 19Z. IN
THE WARM SECTOR, SURFACE TEMPERATURES WERE NEAR 90 DEG F WITH DEW
POINTS IN THE MID 60S. AS A MID/UPPER-LEVEL TROUGH CROSSES THE
NORTHERN ROCKIES THIS AFTERNOON (EVIDENT ON LATEST WV IMAGERY),
LOW-LEVEL SOUTHERLY FLOW ACROSS THE PLAINS IS GRADUALLY
STRENGTHENING, WITH 850 HPA FLOW OF 40-45 KT INDICATED ACROSS THE
DAKOTAS ON THE LATEST SPC MESOANALYSIS. LIFTING OF THIS AIR ACROSS
THE WARM FRONT IS PRODUCING SHOWERS AND THUNDERSTORMS ACROSS NORTH
DAKOTA, WITH SOME TRAINING OF CONVECTIVE CELLS ALREADY OBSERVED.
RAINFALL RATES OF 1-1.5 IN/HR WERE ESTIMATED BY RADAR IN THE
CONVECTION ONGOING ACROSS WESTERN ND. SOME HAIL CONTAMINATION
APPEARS LIKELY, SO ACTUAL RATES ARE LIKELY CLOSER TO 1 IN/HR.

AS THE UPPER TROUGH CONTINUES TO MOVE EAST AND HEIGHTS FALL,
CONVECTION SHOULD CONTINUE TO INCREASE IN COVERAGE, AND A SLIGHT
NEGATIVE TILT ALOFT MAY SLOW THE EASTWARD PROGRESSION OF
CONVECTION FOR A PERIOD OF TIME, RESULTING IN A CONTINUED RISK OF
TRAINING CELLS UNTIL 00-01Z. A NUMBER OF HI-RES MODELS SHOW THE
POTENTIAL FOR RATES OF 1-1.5 IN/HR, AND AREAS OF 2-3 INCH RAINFALL
TOTALS OVER THE NEXT SEVERAL HOURS. FLASH FLOODING IS POSSIBLE.

RYAN

ATTN...WFO...BIS...

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

LAT...LON   49290195 49000074 48170024 47110001 46320030
            46070088 46150194 46740269 47480317 48260320
            48910313 49190288