MESOSCALE PRECIPITATION DISCUSSION 0318
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1002 PM EDT MON AUG 25 2014
 
AREAS AFFECTED...WRN AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 260201Z - 260501Z
 
SUMMARY...DEEPLY ESTABLISHED OUTFLOWS AND UNSTABLE AIR WILL
SUPPORT CONTINUED THUNDERSTORMS WITH HEAVY RAINFALL THROUGH 05Z.
FLASH FLOODING IS POSSIBLE.

DISCUSSION...LOOSELY ORGANIZED THUNDERSTORM CLUSTERS/COMPLEXES
WERE INITIATED FROM THE SOUTHEAST AZ MOUNTAINS...MOVING WEST...AND
FROM SOUTHERLY UPSLOPE INTO THE MOUNTAINS IN WESTERN AZ...WITH
PROPAGATION TOWARD THE SOUTHEAST. THE RAPIDLY UPDATING GUIDANCE
HAS NOT HANDLED THIS WELL...ESPECIALLY IN WESTERN AZ. RADAR TRENDS
SUGGEST HEALTHY COLD POOLS EXIST...AND THEY MAY BE CAPABLE OF
PUSHING THROUGH THE AXIS OF UNUSUALLY MOIST AND UNSTABLE AIR IN
PLACE ACROSS THE LOWER ELEVATIONS NEAR AND WEST OF PHOENIX. THE
HRRR FORECASTS MIXED LAYER CAPE OF 1000 J/KG TO REMAIN THROUGH
05Z...WHILE THE RAP ACTUALLY FORECASTS INFLOW/850 WINDS TO
INCREASE INTO THE WESTERN COMPLEX...PERHAPS OFFSETTING THE ONSET
OF GREATER INHIBITION. THOUGH THE 12Z HI-RES MODELS HAVE NOT
HANDLED TIMING...THEY WERE CONSISTENT IN PREDICTING COLD POOLS TO
GRADUALLY CONSUME THE AVAILABLE CAPE...CONCLUDING WITH A LOCAL
MAXIMUM IN ACTIVITY NEAR PHOENIX.

RADAR AND SATELLITE TRENDS SUGGESTED RECENT MAINTENANCE OF
INTENSITY IN BOTH WESTERN AND SOUTERN AZ AT 02Z...ALONG WITH
INCREASED AVAILABILITY OF UNSTABLE AIR WITH CONGESTUS FORMING AT
INCREASINGLY LOW LATITUDE IN WESTERN AZ. MUCH OF THE ACTIVITY WAS
AT LONG RANGE FROM RADARS...BUT EVEN TAKING A CONSERVATIVE
TWO-THIRDS OF THE DUAL-POL ESTIMATES SUGGESTS ISOLATED 2 INCH
RAINFALL HAS OCCURRED...AND WILL REMAIN POSSIBLE.

BURKE

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

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

LAT...LON   34171147 33191108 32291119 31631181 31661256 32061345
            32801416 33531430 34271389 34701308 34631200 34171147