MESOSCALE PRECIPITATION DISCUSSION 0362
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 PM EDT SAT JUL 18 2015
 
AREAS AFFECTED...MUCH OF AZ... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 190300Z - 190700Z
 
SUMMARY...ACTIVE CONVECTION CONTINUES ACROSS MUCH OF
WESTERN/CENTRAL AZ WHERE LOCAL HOURLY RAINFALL RATES HAVE
APPROACHED THE 1 TO 2 INCH RANGE. IN RECENT HOURS...CONVECTION HAS
SHIFTED ITS FOCUS INTO REGIONS OF SOUTHWESTERN TO SOUTH-CENTRAL AZ
WHERE GREATER INSTABILITY RESIDES. FLASH FLOODING IS
POSSIBLE...PARTICULARLY IN LOCATIONS WHICH EXPERIENCED EARLIER
HEAVY RAINFALL.

DISCUSSION...RELATIVE TO THE PAST SEVERAL HOURS...THE AREAL
COVERAGE OF THUNDERSTORMS HAS SHIFTED FOCUS FROM SOUTHERN CA
TOWARD AZ. CURRENT RADAR IMAGERY THIS EVENING SHOWS THE BETTER
ORGANIZATION ACROSS THE MOGOLLON RIM WHICH SEEMS TO BE ENHANCED BY
LOCAL TERRAIN EFFECTS. FARTHER TO THE SOUTH...STRENGTHENING
UPDRAFTS WERE EVIDENT ACROSS SOUTHWESTERN AZ WHERE CLOUD TOPS WERE
COOLING. THIS LOCATION SEEMS TO BE FAVORED GIVEN GREATER
INSTABILITY HAS DEVELOPED IN THE PRESENCE OF SUFFICIENT SURFACE
HEATING EARLIER THIS AFTERNOON. THE 01Z RAP FORECAST DOES SHOW THE
AREA BECOMING MORE STABLE IN TIME WHICH SUPPORTS THE NOTION THE
ACTIVITY WILL LIFT NORTHWARD INTO THE STRONGER BUOYANCY ACROSS
WEST-CENTRAL AZ.

RECENT VIEWS OF THE BLENDED-TPW PRODUCT SUPPORTS A RELATIVELY
SHARP CUT-OFF IN THE TROPOSPHERIC MOISTURE PROFILE. THE GPS DATA
THIS EVENING INDICATES ABOVE 1.75 INCH PWATS ANCHORING THE
SOUTHERN HALF OF AZ WHILE VALUES IN THE 0.75 TO 1.00 INCH RANGE
RESIDE ALONG THE NORTHERN EXTENT OF THE STATE. IT APPEARS THE
BETTER MOISTURE INCREASES HAVE BEEN CONFINED TO CA WITH 0.50 INCH
PWAT RISES IN THE PAST 9 HOURS. GIVEN ALL THIS
INFORMATION...DECIDED TO TRUNCATE THE NORTHERN BOUNDARY OF THIS
MPD AREA...THUS KEEPING IT SOUTH OF THE UT BORDER.

OVERALL...HIGH-RESOLUTION MODELS HAVE NOT DONE A GREAT JOB WITH
FORECASTING THE LOCATION OF CONVECTION...NOR AMOUNTS. JUST
FOCUSING ON THE FACT THERE IS PLENTY OF MOISTURE AND REMNANT
INSTABILITY IN PLACE...FEEL A FLASH FLOOD THREAT EXISTS FOR AT
LEAST 3 TO 4 MORE HOURS.


RUBIN-OSTER

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

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

LAT...LON   36491196 36461094 35801019 35141022 34551058 
            33301164 31551254 32051404 33561410 34911365 
            36081282