Weather Service Report


002 
FXUS65 KPSR 301123
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
423 AM MST SUN AUG 30 2015

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS... 
THERE WILL CONTINUE TO BE SUFFICIENT MOISTURE EAST OF THE LOWER 
COLORADO RIVER TO SUPPORT ISOLATED AFTERNOON AND EVENING 
THUNDERSTORMS TODAY. DRIER WESTERLY FLOW WILL SLOWLY PUSH THE 
MOISTURE TO THE EAST BY TUESDAY...LIMITING STORM CHANCES PRIMARILY 
TO HIGHER TERRAIN AREAS TO THE EAST OF PHOENIX. THERE WILL ALSO BE A 
GRADUAL COOLING TREND THIS WEEK WITH CENTRAL DESERTS HIGH 
TEMPERATURES DROPPING TO AROUND SEASONAL NORMALS BY THE MIDDLE OR 
LATTER PORTION OF THE WEEK.

&&

.DISCUSSION... STRONG UPPER LEVEL ANTICYCLONE REMAINS IN PLACE 
ACROSS THE DESERT SOUTHWEST...AND WITH H5 HEIGHTS OVER THE LOWER 
DESERTS AT 594DM HIGH TEMPERATURES YESTERDAY REACHED OR EXCEEDED 110 
OVER THE HOTTER LOWER DESERTS. PHOENIX REACHED 111 YESTERDAY. 
HEIGHTS ARE EXPECTED TO FALL SLIGHTLY TODAY AS TROFFING ALOFT 
DEVELOPS ALONG THE WEST COAST...BUT HIGH TEMPS WILL ONLY FALL A FEW 
DEGREES AND SHOULD REMAIN WELL ABOVE SEASONAL NORMALS. MOISTURE 
REMAINS ELEVATED ACROSS CENTRAL AND EASTERN AZ...WITH PWAT BETWEEN 
1.25 AND 1.5 INCHES. 2 AM SURFACE DEWPOINTS OVER THE LOWER DESERTS 
WERE MOSTLY IN THE 60S. SO...DESPITE STEERING FLOW BECOMING MORE 
SOUTHWESTERLY TODAY IT WILL NOT BE STRONG ENOUGH TO SCOUR OUT THE 
MOISTURE OVER SOUTH CENTRAL AZ. THERE WILL BE SUFFICIENT 
MOISTURE...INSTABILITY...MLCAPE AND HEATING TO ALLOW FOR YET ANOTHER 
ROUND OF CONVECTION FROM PHOENIX EASTWARD THIS AFTERNOON AND 
EVENING. LOCAL MESOSCALE MODELS SUCH AS THE WRF4KM SUGGEST THE 
CENTRAL DESERTS WILL SEE MORE THUNDERSTORMS MAINLY DURING THE 
EVENING HOURS TONIGHT. THUS...POPS REMAIN AROUND 20 PERCENT OR 
HIGHER FROM PHOENIX EAST LATER THIS AFTERNOON AND EVENING. 

STARTING ON MONDAY...OPERATIONAL RUNS OF THE GFS AND ECMWF AS WELL 
AS ENSEMBLE GUIDANCE CONTINUE TO CALL FOR THE START OF A GRADUAL 
DRYING AND COOLING TREND AS TROFFING ALOFT SETS UP ALONG THE WEST 
COAST AND GIVES A DEEP SOUTHWESTERLY FLOW ALOFT TO SERN CA AND 
ARIZONA. THIS FLOW WILL GRADUALLY PUSH MOISTURE OFF TO THE 
EAST...AND BY TUESDAY THUNDERSTORMS CHANCES WILL BE PRIMARILY 
CONFINED TO HIGHER TERRAIN AREAS EAST OF PHOENIX. BY MIDWEEK THERE 
WILL ONLY BE A SLIGHT CHANCE FOR AFTERNOON/EVENING STORMS OVER 
SOUTHERN GILA COUNTY IN AREAS EAST OF GLOBE. EXCEPT FOR SOME HIGH 
CLOUDS AT TIMES MOVING THROUGH THE SOUTHWEST FLOW ALOFT SKIES WILL 
BE MOSTLY SUNNY OVER THE LOWER DESERTS THROUGH MOST OF THE WORK 
WEEK. AS HEIGHTS SLOWLY LOWER...HIGH TEMPERATURES WILL DROP OFF DAY 
BY DAY. MONDAY WILL STILL SEE HIGH TEMPS WELL ABOVE NORMAL WITH 
HIGHS AROUND 107 EXPECTED AT PHOENIX BUT BY WEDNESDAY THE CENTRAL 
DESERTS SHOULD LOWER TO AROUND 104 DEGREES WITH LITTLE CHANGE THEN 
EXPECTED INTO THE WEEKEND.

THERE IS A BIT OF A WRINKLE IN THE FORECAST OUT AT THE END OF THE 
EXTENDED PERIOD...OVER THE COMING WEEKEND...AS MEDIUM RANGE MODELS 
CONTINUE TO CALL FOR SOME TROPICAL MOISTURE TO BE DRAWN NORTHWARD BY 
THE BROAD TROF OVER THE WESTERN CONUS...AND THEN SPREAD INTO THE 
LOWER ARIZONA DESERTS LEADING TO AT LEAST A SLIGHT CHANCE OF 
AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS BY SATURDAY. POPS 
HAVE BEEN RAISED OVER THE WEEKEND ACCORDINGLY...AND WILL BE SLIGHTLY 
GREATER THAN CLIMO VALUES FOR NOW.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
STORMS HAVE LONG SINCE DISSIPATED BUT A FEW MID CLOUDS WILL LINGER
THROUGH THE REST OF THE MORNING. EXPECTING ANOTHER ROUND OF LATE-DAY
STORMS CIRCLING THE VALLEY...POSSIBLY ENCROACHING UPON KIWA AFTER
02Z-03Z. OUTFLOWS A POSSIBILITY AT ALL PHOENIX TERMINALS AND I
INDICATED AN EARLIER THAN USUAL SOUTHEASTERLY SHIFT IN WIND
DIRECTIONS. 

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH... 
NO WEATHER-RELATED AVIATION IMPACTS EXPECTED AT IPL OR BLH THROUGH AT
LEAST MONDAY MORNING. 
 
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
 
&&

.FIRE WEATHER... 
TUESDAY THROUGH SATURDAY...
A LOW PRESSURE SYSTEM ACROSS THE PACIFIC NORTHWEST WILL DISPLACE THE
MONSOON HIGH TO THE SOUTH AND EAST THROUGH THE WEEK. THE TREND WILL
BE TOWARDS COOLER AND DRIER CONDITIONS ACROSS THE DESERT SOUTHWEST.
HOWEVER...ENOUGH MOISTURE WILL LINGER ACROSS EASTERN ARIZONA FOR
ISOLATED AFTERNOON THUNDERSTORMS.

&&
 
.SPOTTER INFORMATION STATEMENT... 
SPOTTERS ARE ENCOURAGED TO REPORT CONDITIONS ACCORDING TO STANDARD
OPERATING PROCEDURES.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...BRECKENRIDGE
AVIATION...LEINS
FIRE WEATHER...HIRSCH

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