MESOSCALE PRECIPITATION DISCUSSION 0495
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
856 PM EDT SUN JUL 16 2017

AREAS AFFECTED...CNTRL/SRN/SERN AZ

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

VALID 170054Z - 170630Z

SUMMARY...AN INCREASING THREAT FOR SCATTERED FLASH FLOODING SHOULD
DEVELOP OVER PORTIONS OF CNTRL AND SERN AZ THROUGH 06Z. SLOW
MOVEMENT/BRIEF TRAINING OF CELLS MAY CONTAIN RAINFALL RATES OF 1
TO 1.5 IN/HR.

DISCUSSION...ANOMALOUSLY HIGH PRECIPITABLE WATER VALUES...1.7 TO
1.9 INCHES...ARE IN PLACE ACROSS THE SRN HALF OF AZ. THE 00Z RAOB
FROM TUS MEASURED 1.72 INCHES WITH NEARLY 1500 J/KG OF CAPE AND
LITTLE TO NO CIN. JUST SOUTH OF THE AZ/MX BORDER WAS A SOMEWHAT
ILL DEFINED LOW CENTERED NEAR 700 MB WITH A WELL DEFINED TROUGH
AXIS AND WIND SHIFT EXTENDING NEWD FROM THE LOW CENTER. REGIONAL
RADAR IMAGERY SHOWED WIDELY SCATTERED THUNDERSTORMS IN PLACE
ACROSS E-CNTRL AND SERN AZ...MOVING WSW AT 5-15 KT AND A RECENT
UPTICK IN CONVECTION WAS NOTED OVER SERN PINAL COUNTY AT 0030Z.

AS THE LOW/TROUGH CONTINUES TO SLOWLY MOVE WEST...RECENT RUNS OF
THE HRRR AND MORE NOTABLY THE ESRL EXPERIMENTAL HRRR HAVE BEEN
ADVERTISING AN INCREASE IN CONVECTION OVER THE HIGHER TERRAIN OF
SERN AZ BETWEEN 02Z AND 03Z. INITIAL CELLS ARE EXPECTED TO EXHIBIT
SLOW MOVEMENT OVER SERN AZ BUT DEWPOINT DEPRESSIONS OF 30-40F ARE
IN PLACE TO THE WEST NOTED WITH CGZ AND SURROUNDING STATIONS WHICH
MAY PROMOTE OUTFLOW DOMINANCE. WHILE CONFIDENCE IS ONLY MODERATE
WITH THE EXPECTED COVERAGE OF CONVECTION GOING PAST 03Z
TONIGHT...A SLIGHT INCREASE IN 700 MB WINDS FROM THE NORTHEAST
OVERNIGHT WOULD SUPPORT SOME BRIEF TRAINING AND LOCALLY HEAVY
RAINFALL RATES THROUGH 06Z BEFORE STORMS POTENTIALLY PROPAGATE TO
THE WEST IN A MORE PROGRESSIVE MANNER.

OTTO

ATTN...WFO...FGZ...PSR...TWC...

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

LAT...LON   34281114 34111019 33390932 32040919 31270985
            31261141 31611273 32471322 33301278 34051198