MESOSCALE PRECIPITATION DISCUSSION 0524
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
117 PM EDT FRI JUL 21 2017

AREAS AFFECTED...PORTIONS OF THE WY BASIN, CO PLATEAU, & CO
ROCKIES

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

VALID 211716Z - 212316Z

SUMMARY...SHOWER AND THUNDERSTORM ACTIVITY IS STARTING TO BUILD
NEAR THE WY BASIN, WHILE OTHER SHOWER ACTIVITY STARTING TO FORM IN
WESTERN CO.  HOURLY RAIN RATES TO 1.5", WITH LOCAL AMOUNTS TO 3",
ARE POSSIBLE.

DISCUSSION...SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE A
COLD FRONT SLOWLY WORKING ITS WAY THROUGH SOUTHWEST WY AND
NORTHERN UT.  DIVERGENCE ALOFT IS BEING AIDED BY THE BASE OF AN
UPPER TROUGH ACROSS WESTERN MT AND AN APPARENT MCV IN WESTERN CO. 
PRECIPITABLE WATER VALUES ARE 0.7-1.1" IN THIS REGION.  ML CAPE
VALUES ARE RISING ABOVE 500 J/KG, WITH MU CAPE VALUES > 1000 J/KG
IN SOUTHWEST WY.  EFFECTIVE BULK SHEAR IS 25-30 KTS IN THE WYOMING
BASIN.

THE MESOSCALE GUIDANCE LOOKS PLAUSIBLE CONCERNING CONVECTIVE
EXPECTATIONS OVER THE NEXT SEVERAL HOURS.  CONVECTION IS EXPECTED
TO FORM NEAR AND DOWNWIND OF THE CO ROCKIES, THE TERRAIN OF UT
(INCLUDING THE UINTAS), AND NEAR THE STALLING FRONT AND MOVE
ROUGHLY EASTWARD AT 10-15 KTS IN THE NORTHERN PART OF THE AREA
WITH SLOWER MOTIONS EXPECTED TOWARDS THE FOUR CORNERS.  ABOVE THE
BOUNDARY LAYER, THE FLOW LOOKS FAIRLY UNIDIRECTIONAL WITH HEIGHT
WHICH COMBINED WITH THE BULK SHEAR WOULD ALLOW FOR THE FORMATION
OF SHORT TRAINING CONVECTIVE BANDS, WHICH THERE HAS BEEN HINTS OF
IN WY SO FAR THIS MORNING.  WITH ML CAPE VALUES RISING ANOTHER
1000+ J/KG INTO THE AFTERNOON AND PRECIPITABLE WATER VALUES 1.5-3
SIGMAS ABOVE THE MEAN FOR LATE JULY, HOURLY RAIN RATES UP TO 1.5"
WITH LOCAL AMOUNTS TO 3", PARTICULARLY IN THE UINTAS AND CO
ROCKIES, ARE POSSIBLE.

ROTH

ATTN...WFO...BOU...CYS...GJT...PUB...RIW...SLC...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...

LAT...LON   42680747 41530556 40210534 38730520 38130620
            37410733 37670893 37710982 37931190 39461164
            40451159 41901038 42440938 42630865