MESOSCALE PRECIPITATION DISCUSSION 0602
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
316 PM EDT SUN JUL 30 2017

AREAS AFFECTED...PORTIONS OF SOUTHERN AND CENTRAL AZ...FAR
SOUTHWEST NM

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

VALID 301915Z - 310115Z

SUMMARY...SLOW MOVING CONVECTION IN THE MONSOONAL MOISTURE CHANNEL
POSES A FLASH FLOOD THREAT THIS AFTERNOON...PARTICULARLY IN AREAS
THAT RECEIVED HEAVY RAINFALL SATURDAY AFTERNOON AND EVENING.

DISCUSSION...CONVECTION IS BEGINNING TO INITIATE OVER THE HIGHER
TERRAIN OVER SOUTHEAST AZ...WHERE THE EXPERIMENTAL GOES-16 CLEAN
IR LOOP SHOWED RAPIDLY COOLING TOPS. THE CONVECTION IS FORMING IN
AN AREA OF 1000-1500 J/KG MLCAPE...WITH NO REMAINING CIN. THE
CONVECTION IS ALSO FIRING ON THE PRECIPITABLE WATER
GRADIENT...WITH VALUES NEAR 1.50 INCHES OVER THE HIGHER TERRAIN IN
SOUTHEAST AZ. THE KEMX RADAR SHOWED HOURLY RAINFALL RATES NEAR AN
INCH WITH THE NEWLY DEVELOPED CONVECTION. THE MOST RECENT HRRR
SHOWED THE POTENTIAL FOR LOCAL 2.00+ INCH RAINFALL AMOUNTS...
ESPECIALLY NEAR THE TERRAIN... WHERE THE CONVECTION WILL BE TIED
FOR A TIME.

SOUTHEAST AZ MAY SEE AN ENHANCED THREAT FOR FLASH FLOODING...AS
THIS AREA HAS SEEN ROUNDS OF CONVECTION OVER THE PAST TWO NIGHTS.
THE LATEST HRRR PERCENT OF SOIL SATURATION PRODUCT INDICATED THAT
THIS AREA MAY BE NEARLY SATURATED IN SPOTS OVER THE HIGHER TERRAIN.

FURTHER NORTH AND WEST...THE AIRMASS IS STILL CAPPED...PER RAP
SOUNDINGS. CLOUDS HAVE BEEN SLOWER TO CLEAR ACROSS SOUTHWEST  AND
CENTRAL AZ THIS MORNING (DUE TO CONVECTION EARLY THIS
MORNING)...AND THE CIN HAS REMAINED IN PLACE. HOWEVER...AS THE
CLOUD THIN...HEATING SHOULD ERODE THE REMAINING CIN...AND
CONVECTIVE INITIATION IS EXPECTED.

VISIBLE SATELLITE IMAGES SHOWED AN OLD MCV OVER SOUTHWEST AZ...AND
THIS FEATURE COULD AID IN FOCUSING MOISTURE AND INSTABILITY ACROSS
THIS AREA. MOISTURE VALUES ARE MUCH HIGHER IN SOUTHWEST AZ...WITH
PRECIPITABLE WATER VALUES NEAR 2.00 INCHES. THERE IS MORE IN THE
WAY OF MID LEVEL FLOW OVER SOUTHWEST AZ...AND THE MOTION COULD
PRECLUDE A LARGER FLASH FLOOD THREAT THIS AFTERNOON. STILL...DUE
TO THE HIGHER MOISTURE CONTENT OF THE AIR...LOCAL 2.00+ INCH
RAINFALL AMOUNTS ARE POSSIBLE HERE AS WELL.

AS THE INSTABILITY BECOMES EXHAUSTED AFTER 31/01Z...THE FLASH
FLOOD THREAT SHOULD START TO WANE.

HAYES

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

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

LAT...LON   35551186 35151122 34821085 34090971 33440947
            32600914 32190882 31570877 31290924 31311033
            31841241 32331340 32951311 33601222 34491203
            35061203