MESOSCALE PRECIPITATION DISCUSSION 0512
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
518 PM EDT WED JUL 19 2017

AREAS AFFECTED...CENTRAL/EASTERN UT...WESTERN/CENTRAL
CO...SOUTHERN WY

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 192115Z - 200315Z

SUMMARY...SHOWERS AND THUNDERSTORMS WITH ENHANCED RAINFALL RATES
ARE EXPECTED THIS AFTERNOON AND EVENING. POCKETS OF FLASH FLOODING
ARE LIKELY.

DISCUSSION...CLUSTERS OF THUNDERSTORMS CONTINUE TO DEVELOP AND
EXPAND IN COVERAGE OVER THE HIGHER TERRAIN OF THE WASATCH AND
ADJACENT UINTA RANGE OF UT...AND ALSO FARTHER EAST ACROSS THE
CENTRAL/WESTERN CO HIGH COUNTRY AND PARTS OF SOUTHERN WY. THIS IS
BEING FACILITATED BY STRONG DIURNAL HEATING...OROGRAPHIC
FORCING/TERRAIN INDUCED CIRCULATIONS AND ALSO THE INCREASED
CONCENTRATION OF MONSOONAL MOISTURE. IN FACT...THE GOES-15 SOUNDER
AND CIRA-LPW DATA SHOW A WELL-DEFINED CHANNEL OF DEEPER MONSOONAL
MOISTURE WRAPPING AROUND THE NORTHWEST FLANK OF THE MID LEVEL
SUBTROPICAL RIDGE THAT IS NOSED WEST INTO THE FOUR CORNERS REGION.
SOME OF THE PWATS OVER CENTRAL/EASTERN UT AND WESTERN CO ARE
RUNNING UP BETWEEN 1 AND 1.25 INCHES WHICH IS A SOLID 2 TO 3
STANDARD DEVIATIONS ABOVE NORMAL.

THE GLOBAL MODELS INDICATE A FURTHER ENHANCEMENT AND CONCENTRATION
OF MONSOONAL MOISTURE THROUGH THE EVENING ACROSS THE MPD THREAT
AREA...AND A CONSENSUS OF THE HIRES MODELS FROM 12Z INCLUDING THE
ARW/NMMB AND NSSL-WRF ALL SUPPORT A CONTINUED EXPANSION OF
THUNDERSTORM ACTIVITY WITH LOCALLY VERY HEAVY RAINFALL. IN
FACT...THE GUIDANCE SUPPORTS AT LEAST LOCALIZED 2 TO 4 INCH
AMOUNTS...WHICH WILL BE SUPPORTED BY HOURLY RAINFALL RATES OF 1.5
TO 2 INCHES/HR WITHIN THE STRONGEST CONVECTIVE CORES AND
ESPECIALLY WITH THE LEVEL OF DEEPER MOISTURE IN PLACE IN THE
700/300 MB LAYER.

THESE RAINFALL AMOUNTS ARE LIKELY TO RESULT IN SOME AREAS OF FLASH
FLOODING AND ESPECIALLY OVER AREAS OF STEEPER TERRAIN AND ADJACENT
CANYON AREAS WHERE WATER WILL BE CHANNELED VERY EFFICIENTLY
DOWNSTREAM. WILL CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   41940644 41540558 40700519 39870513 39130536
            38550576 38060623 37600700 37510797 38010971
            37891135 37741212 38241267 39121258 40261198
            40711149 41081093 41530977 41920813