MESOSCALE PRECIPITATION DISCUSSION 0456
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 PM EDT SUN JUL 15 2018

AREAS AFFECTED...SOUTHERN UT...NORTHERN/EASTERN
AZ...WESTERN/SOUTHERN NM

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

VALID 151755Z - 152315Z

SUMMARY...CONVECTIVE INITIATION WILL ENSUE OVER THE NEXT 1 TO 2
HOURS...WITH NUMEROUS SHOWERS AND THUNDERSTORMS EXPECTED BY EARLY
TO MID-AFTERNOON. FLASH FLOODING WILL BE LIKELY GIVEN DEEP
MONSOONAL MOISTURE PROFILES.

DISCUSSION...THE LATEST GOES-16 VISIBLE SATELLITE IMAGERY IS
SHOWING PLENTY OF CU/TCU INITIATING OVER PORTIONS OF SOUTHERN
UT...NORTHERN/EASTERN AZ AND WESTERN/SOUTHERN NM ALONG WITH SOME
POCKETS OF CONVECTIVE INITIATION OVER THE HIGHER TERRAIN AS STRONG
DIURNAL HEATING IS PROMOTING AN INCREASINGLY UNSTABLE BOUNDARY
LAYER. MLCAPE VALUES ARE ALREADY ON THE ORDER OF 1000 TO 1500 J/KG
LOCALLY...AND WITH A DEEP MONSOONAL MOISTURE PROFILE IN PLACE
ACROSS THE SOUTHWEST...IT WILL NOT TAKE MUCH MORE ADDITIONAL
HEATING FOR A MORE ROBUST EXPANSION OF CONVECTION TO BEGIN TO TAKE
PLACE.

THE PWATS ACROSS THE REGION AGAIN ARE QUITE ANOMALOUS...AND AS
MUCH AS 2 TO 2.5 STANDARD DEVIATIONS ABOVE NORMAL FOR THIS TIME OF
THE YEAR...AND GIVEN THE CONCENTRATION OF MOISTURE SEEN IN THE
500/300 MB LAYER VIA 12Z RAOB DATA FROM FGZ/PHX AND TUS...THE
ANTICIPATED CONVECTION TODAY WILL AGAIN BE HIGHLY EFFICIENT AND
CAPABLE OF PRODUCING VERY HEAVY RAINFALL RATES THAT COULD EXCEED 2
INCHES/HR.

THE HIRES CAM GUIDANCE FROM 12Z COLLECTIVELY SUPPORTS LOCALLY VERY
HEAVY RAINFALL TOTALS THAT MAY REACH AS HIGH AS 3 TO 4 INCHES
GOING THROUGH LATE-AFTERNOON...WITH THE GREATEST CONCENTRATION OF
CONVECTION EXPECTED TO BE OVER CENTRAL/NORTHERN AZ IN VICINITY OF
THE MOGOLLON RIM AND NORTH OF A WELL-DEFINED MCV. THE HEAVIER
RAINFALL POTENTIAL IS SUPPORTED NOT ONLY BY THE INTENSE RAINFALL
RATES...BUT ALSO THE EXPECTED SLOW CELL MOTIONS SINCE THE FLOW
THROUGH THE COLUMN IS QUITE WEAK.

FLASH FLOODING WILL BE LIKELY GIVEN THE HEAVY SHORT-TERM RAINFALL
RATES. THE MORE SUSCEPTIBLE AREAS TO FLASH FLOODING WILL AGAIN BE
SLOT-CANYONS...DRY WASHES AND ANY BURN SCARS. AREAS DOWNSTREAM
FROM ACTIVE THUNDERSTORMS MAY ALSO SEE FLASH FLOODING GIVEN
ENHANCED RUNOFF AND FLOOD WAVE CONCERNS ON AREA TRIBUTARIES. WILL
CONTINUE TO MONITOR THROUGH THE AFTERNOON.

ORRISON

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

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

LAT...LON   39011169 38371110 36811070 36060908 35190793
            34710695 34560581 34270526 33680506 33050512
            32490555 32170717 31460812 31310863 31400952
            31900993 32841050 33421127 34101226 35131313
            35971352 37181351 38751254