MESOSCALE PRECIPITATION DISCUSSION 0609
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
532 PM EDT MON JUL 31 2017

AREAS AFFECTED...SOUTHERN UT...NORTHWEST AZ

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

VALID 312130Z - 010130Z

SUMMARY...SLOW MOVING CONVECTION TRAINING ACROSS SOUTHERN UT INTO
NORTHWEST AZ ON A LOW LEVEL CONVERGENCE AXIS COULD RESULT IN A
FLASH FLOOD THREAT THIS AFTERNOON.

DISCUSSION...REGIONAL RADARS SHOWED CONVECTION DEVELOPING ON A LOW
LEVEL CONVERGENCE AXIS EXTENDING FROM CENTRAL UT INTO NORTHWEST
AZ. THE CONVECTION IS FORMING IN A RIBBON OF 500-1000 J/KG
MLCAPE...AS THE LAST OF THE LOW LEVEL CIN IS ERASED. THE MOST
RECENT EXPERIMENTAL GOES-16 CLEAN IR LOOP SHOWED SLOWLY COOLING
TOPS ALONG THE AXIS...AND THE KICX RADAR SHOWED HOURLY RAINFALL
RATES NEAR AN INCH WITH THE MOST RECENT ACTIVITY.

THE CONVECTION IS FORMING IN AN AREA WITH 850-300 MB MEAN WINDS
ARE LESS THAN 10 KNOTS...WHICH WILL PROMOTE TRAINING ALONG THE
AXIS OF LOW LEVEL CONVERGENCE. MOISTURE MAY BE A LIMITING FACTOR
FOR A MORE ORGANIZED FLASH FLOOD THREAT...WITH PRECIPITABLE WATER
VALUES ALONG THE AXIS GENERALLY BELOW 1.10 INCHES.

MOST OF THE HIGH RESOLUTION GUIDANCE IS EITHER MISSING THE
CONVECTIVE DEVELOPMENT OR HAS UNDERPLAYED IT. THE MOST RECENT HRRR
HAS AN AXIS OF LOCAL 1.00 INCH QPF ON THIS AXIS. ONE HOUR FLASH
FLOOD GUIDANCE IS AS LOW AS AN INCH HERE...SO ANY CONVECTION ON
THE AXIS COULD RESULT IN A FLASH FLOOD THREAT INTO THE LATER
AFTERNOON.

HAYES

ATTN...WFO...FGZ...GJT...SLC...VEF...

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

LAT...LON   39451047 38580980 38061017 36791169 36131271
            36401327 37961289 39061191