MESOSCALE PRECIPITATION DISCUSSION 0503
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
140 AM EDT TUE JUL 18 2017

AREAS AFFECTED...SOUTH CENTRAL ARIZONA

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

VALID 180545Z - 181100Z

SUMMARY...MCS DEVELOPING OVER PINAL MTNS EXPECTED TO ROLL THROUGH
SONORAN DESERT WITH LOCALIZED FLASH FLOODING POTENTIAL.

DISCUSSION...GOES-16 EXPERIMENTAL WV LOOPS DEPICT A DEVELOPING
FAVORABLE ENVIRONMENT FOR CONVECTIVE COMPLEX DEVELOPMENT EVEN IN
WEAK FLOW REGIME.  COMPACT ANTICYCLONE OVER NW AZ AND APPROACHING
WAVE OVER N CHIHUAHUA ALLOW FOR MODEST CONFLUENT JET STREAK ACROSS
E CENTRAL AZ THAT BECOMES INCREASINGLY DIFFLUENT ACROSS THE
EASTERN VALLEY.  VWP FROM KIWA AND KEMX SUGGEST WEAK 850MB UPSLOPE
FLOW IN ADVANCE OF DEVELOPING CONVECTION OVER THE S PINAL
MOUNTAINS.  RECENT IR TOPS HAVE COOLED TO -75C SUPPORTING THIS
INCREASED CONVECTIVE ENVIRONMENT.  03Z SPECIAL ROAB WEST OF
PHOENIX ADJUSTED FOR SFC CONDITIONS OVER E PINAL COUNTY SUPPORT AN
AREA OF 2000 J/KG WITH TDS IN THE UPPER 60S AND 850MB MST AXIS
(PER RAP ANALYSIS) SHOWING AN ENHANCED TONGUE OF +16C TDS FROM N
PIMA THROUGH THIS COMPLEX TO CATRON COUNTY NM AND TPW VALUES
NOSING TOWARD 2" ALL SUPPORT INCREASING RAINFALL EFFICIENCY FOR
THIS COMPLEX AS IT ROLLS INTO LOWER TERRAIN IN PINAL. GIVEN LOW
LEVEL ENVIRONMENT/WEAK FLOW CELL MOTIONS SHOULD BE TOWARD THE
INSTABILITY/MOISTURE AXIS AND GIVEN SOME FORWARD PROPAGATION OF
5-10KTS LIKELY LEADING TO OVERALL SPEEDS OF 15-20KT WHICH MAY HELP
WITH SOME OF THE OVERALL TOTALS AND REDUCE FLASH FLOOD RISK EVER
SO SLIGHTLY.  THOUGH CELL MERGERS/COLLISIONS AND SOME REPEAT
TRACKS COULD EQUALLY LEAD TO ISOLATED POCKETS THAT ARE DIFFICULT
TO PINPOINT EVEN A HOUR PRIOR TO SAID OCCURRENCE. 

AS SUCH...03Z ESRL HRRRV3 APPEARS TO BE ONLY GUIDANCE THAT IS
HANDLING THE CURRENT MESO SITUATION...AND IS SUGGESTIVE OF POCKET
OF 1-2" WITH ISOLATED 2.5" ACROSS THE AREA OF CONCERN THROUGH
12Z...GIVEN THE BULK OF THESE TOTALS WILL FALL QUICKLY FLASH
FLOODING CONTINUES TO BE A POSSIBLE. 

OF NOTE: THE HRRRV3 MAY BE OVERDOING THE CONVECTION DEVELOPING
OVER THE PHOENIX METROPLEX.  HOWEVER...ASSIMILATED OUTFLOW
BOUNDARY IS SEEN ON KFSX IN THE PROPER LOCATION ENTERING N GILA
COUNTY AND BEARS WATCHING THOUGH WITH REDUCED INSTABILITY (PER 03Z
SOUNDING) THERE IS A BIT MORE UNCERTAINTY FOR THIS CONVECTIVE TO
COME TO FRUITION. 

GALLINA

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

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

LAT...LON   33861155 33581088 33211018 32541079 31881224
            31971304 32221352 32881332 33821222