MESOSCALE PRECIPITATION DISCUSSION 0473
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
634 PM EDT TUE JUL 17 2018

AREAS AFFECTED...SOUTHEAST MT...WESTERN SD...NORTHEAST WY

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

VALID 172232Z - 180232Z

SUMMARY...SLOW-MOVING AND LOCALLY BACKBUILDING SHOWERS AND
THUNDERSTORMS WILL BRING THE POTENTIAL FOR SOME FLASH FLOODING
CONCERNS OVER THE NEXT FEW HOURS.

DISCUSSION...THE LATEST GOES-16 INFRARED IMAGERY SHOWS A MID LEVEL
VORTMAX SITUATED OVER WEST-CENTRAL MONTANA LATE THIS AFTERNOON,
AND EXPANDING COVERAGE OF SLOW MOVING THUNDERSTORMS WITH
INCREASING ECHO TOPS.  THIS IS ALSO DEPICTED ON REGIONAL DOPPLER
RADARS WITH SLOW MOVING CELLS WITH POSSIBLE CELL MERGERS OVER THE
NEXT FEW HOURS.  ASCENT IS BEING AIDED FURTHER BY SOME LEFT EXIT
JET DYNAMICS APPROACHING THE REGION, AND ALSO THE PRESENCE OF A
STATIONARY FRONT.

A CORRIDOR OF ENHANCED PWS ON THE ORDER OF 1.2 TO 1.4 INCHES IS
ADVECTING INTO THE REGION COURTESY OF MOIST SOUTHEAST INFLOW AT
LOW LEVELS.  MLCAPES OF ROUGHLY 1000-2000 J/KG EXIST PER LATEST
SPC MESOANALYSIS.  GIVEN THE SLOW CELL MOTION AND TENDENCY FOR
CONVECTION TO BACKBUILD, FLASH FLOODING WILL BE POSSIBLE THROUGH
230Z.

D. HAMRICK

ATTN...WFO...BYZ...CYS...GGW...RIW...UNR...

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

LAT...LON   47000608 46790519 45880413 45120296 44950267
            44510210 44130212 43450273 42880329 42880504
            43260620 43830693 44770732 45610787 46430766
            46910698