MESOSCALE PRECIPITATION DISCUSSION 0400
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
455 PM EDT SAT SEP 27 2014
 
AREAS AFFECTED...CNTRL ARIZONA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 272054Z - 280254Z
 
SUMMARY...AS AN AXIS OF MOIST SOUTHERLY FLOW AHEAD OF A PACIFIC
COLD FRONT EDGES EWD ACROSS THE MOGOLLON RIM INTO AN INSTABILITY
AXIS...THE FLASH FLOOD THREAT WILL CONTINUE THROUGH SUNSET ACROSS
A LARGE SECTION OF CNTRL ARIZONA. MOISTURE TRANSPORT NORTH OF THE
THREAT AREA MAY BE INTERRUPTED ENOUGH TO ALLOW FOR MORE STRATIFORM
RAIN WITH EMBEDDED HEAVIER ELEMENTS.

DISCUSSION...REGIONAL RADAR IMAGERY OVER THE PAST SEVERAL HOURS
HAS SHOWN A BROKEN LINE OF HEAVY RAIN SLOWLY MOVING EWD ACROSS WRN
ARIZONA AT ABOUT 20 MPH AHEAD OF A STRONG PACIFIC COLD FRONT. DUAL
POL AND GROUND TRUTH SHOWS 1 HOUR RAINFALL RATES HAVE BEEN BETWEEN
1 AND 1.5 INCHES WITHIN THE HEAVIER CORES. VISIBLE IMAGERY DURING
THE EARLY AFTERNOON HOURS HAS SHOWN MOSTLY CLEAR SKIES ALLOWING
FOR RAP ESTIMATED ML CAPES OF 500 TO 1500 J/KG JUST AHEAD OF THE
COLD FRONT IN CNTRL AND NRN ARIZONA.

DESPITE THE STEADY MOVEMENT OF THE LINE OF HEAVY RAINFALL...AND
DRY AIR NOTED ABOVE 600 MB PER WV IMAGERY AND RAP SOUNDING
ANALYSES...A THREAT FOR FLASH FLOODING WILL CONTINUE THROUGH THE
REMAINDER OF THE AFTERNOON INTO THE EVENING. STRONG DIFFLUENCE
NOTED ON WV IMAGERY APPEARS GREATEST OVER ARIZONA AND HI-RES
MODELS...INCLUDING THE 12Z HRW ARW...NAM CONEST AND NSSL
WRF...SUGGEST CONTINUED RAINFALL RATES OVER 1 IN/HR AND POCKETS OF
2-3 INCHES IN 3 HOURS TIME BEFORE 03Z. THESE SAME HI-RES MODELS
HAVE HANDLED EARLIER RAINFALL ACROSS THE REGION REASONABLY WELL
AND IT IS EXPECTED THEIR PERFORMANCE WILL CONTINUE. LOCATIONS
NORTH OF THE THREAT AREA FROM NRN ARIZONA INTO SRN UTAH ARE
EXPECTED TO SEE REDUCED RAINFALL RATES GIVEN ONGOING CONVECTION
ACROSS CNTRL/SRN ARIZONA RETARDING NWD MOISTURE TRANSPORT WITH
ONLY A LOCALIZED FLASH FLOOD THREAT.

OTTO

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

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

LAT...LON   36431157 35101018 33411010 32411102 32581221 
            33281306 35081310 36161263