MESOSCALE PRECIPITATION DISCUSSION 0608
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
431 PM EDT MON JUL 31 2017

AREAS AFFECTED...PORTIONS OF CENTRAL AND SOUTHERN AZ

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

VALID 312030Z - 010130Z

SUMMARY...SLOW MOVING CELLS...INITIALLY TIED TO THE
TERRAIN...COULD POSE A FLASH FLOOD THREAT IN A HIGH MOISTURE
ENVIRONMENT THROUGH THE AFTERNOON HOURS.

DISCUSSION...REGIONAL RADARS ACROSS SOUTHEAST AND CENTRAL AZ SHOW
CONVECTION DEVELOPING..AS THE LOW LEVEL CIN IS ERODED. AS HAS BEEN
THE CASE THE PAST FEW DAYS... THE CONVECTION IS INITIATING ACROSS
THE HIGHER TERRAIN. WITH MLCAPE VALUES BETWEEN 1500-2000 J/KG
ACROSS SOUTHERN AZ...THE CONVECTIVE COVERAGE IS EXPECTED TO
INCREASE WITH TIME.

PRECIPITABLE WATER VALUES VARY ACROSS SOUTHERN AZ FROM 1.50 OVER
SOUTHEAST AZ TO NEAR 2.00 INCHED ACROSS SOUTHWEST AZ (AS INDICATED
ON 12Z SOUNDINGS OVER THE REGION)....AND THE FIRST ROUND OF STORMS
HAVE PRODUCED HOURLY RAINFALL RATES BETWEEN 1.00 AND 1.50 INCHES
OVER SOUTHERN APACHE COUNTY AZ. 850-300 MB MEAN WIND SPEEDS ARE
LESS THAN 10 KNOTS ACROSS MUCH OF SOUTHERN AZ...AND THE
COMBINATION OF HIGH RAINFALL RATES IN AN ENVIRONMENT OF SLOW CELL
MOTION COULD RESULT IN LOCAL 2.00+ INCHES OF RAINFALL...ESPECIALLY
ACROSS THE HIGHER TERRAIN OF SOUTHEAST AZ. THESE VALUES ARE
CORROBORATED BY THE 12Z WRF ARW...AS WELL AS THE MOST RECENT HRRR
SOLUTION.

PORTIONS OF SOUTHEAST AZ HAS RECEIVED ROUNDS OF HEAVY RAINFALL THE
PAST TWO AFTERNOON/EVENINGS...AND ANY CONVECTION IS THIS AREA
COULD POSE AN ENHANCED FLASH FLOOD THREAT. WHILE THE ACTIVITY MAY
NOT BE MORE THAN SCATTERED AT THE TIME OF PEAKING HEATING...SLOW
CELL MOTIONS IN A HIGH MOISTURE ENVIRONMENT WILL POSE A FLASH
FLOOD THREAT THROUGH THE AFTERNOON HOURS.

HAYES

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

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

LAT...LON   35481133 35111088 35051088 33941078 32590860
            31610818 31280923 31301058 31631201 31931246
            32671288 33561281 34581259 35381207