MESOSCALE PRECIPITATION DISCUSSION 0529
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
854 PM EDT FRI JUL 21 2017

AREAS AFFECTED...WESTERN NM...AZ...FAR SOUTHERN UT...FAR SOUTHWEST
CO

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

VALID 220045Z - 220530Z

SUMMARY...MONSOONAL SHOWERS AND THUNDERSTORMS WILL CONTINUE
THROUGH THE EVENING HOURS...WITH A GRADUAL WEAKENING TREND.
HOWEVER...LOCALLY VERY HEAVY RAINFALL WILL CONTINUE TO FOSTER
CONCERNS FOR FLASH FLOODING.

DISCUSSION...LATE-DAY EXPERIMENTAL GOES-16 0.64 MICRON/VIS
SATELLITE IMAGERY SHOWS BROKEN COVERAGE OF HEAVY SHOWERS AND
THUNDERSTORMS OVER WESTERN NM...A LARGE AREA OF ESPECIALLY
CENTRAL/EASTERN AZ ALONG WITH ADJACENT AREAS OF SOUTHERN UT AND
SOUTHWEST CO.

THE CONVECTION CONTINUES TO EVOLVE WITH A COMBINATION OF DIURNAL
HEATING AND A RATHER DEEP POOL OF MONSOONAL MOISTURE...AS PWATS
CONTINUE TO RANGE FROM 1.5 TO 2.5 STANDARD DEVIATIONS ABOVE
NORMAL. IN ADDITION TO THIS...THERE IS A RATHER BROAD LOW TO MID
LEVEL TROUGH OVER THE REGION WITH A WEAK SURFACE LOW CENTER LOW
JUST NORTH OF WINDOW ROCK LOCATED JUST WEST OF THE AZ/NM BORDER.
THIS IS FACILITATING SOME ADDITIONAL SURFACE CONVEREGENCE FOR SOME
OF THE CONVECTION TO BE CHARACTERIZED BY LOOSELY ORGANIZED BANDS
AND CLUSTERS.

GIVEN THE RATHER DEEP COLUMN OF MONSOONAL MOISTURE...RAINFALL
RATES OF UP TO 2 INCHES/HR WILL REMAIN POSSIBLE WITH THE EVOLUTION
OF THE CONVECTION OVER THE NEXT FEW HOURS. SOME GRADUAL WEAKENING
OF THE CONVECTION SHOULD OCCUR BY LATE EVENING THOUGH AS
INSTABILITY BECOMES INCREASINGLY EXHAUSTED.

HOWEVER...UNTIL THEN THERE WILL BE THE POTENTIAL FOR ADDITIONAL 2
TO 3 INCH RAINFALL AMOUNTS. FLASH FLOODING WILL THUS REMAIN A
CONCERN THIS EVENING OVER AREA DRY WASHES/ARROYOS AND ALSO THE
MORE FAVORED HIGHER TERRAIN AND ADJANCENT SLOT CANYONS.

ORRISON

ATTN...WFO...ABQ...EPZ...FGZ...GJT...PSR...PUB...SLC...TWC...
VEF...

ATTN...RFC...CBRFC...WGRFC...

LAT...LON   38081242 37831183 37691121 37670995 37620857
            37740785 37680712 37050667 35550624 33430620
            32380609 31850654 31640750 31270804 31110891
            31100969 31161034 31241092 31461140 32461135
            32981152 33491188 34241291 34831363 35631399
            36541406 37621359