Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 301006
AFDPSR

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

.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...
THUNDERSTORMS HAVE DISSIPATED ACROSS THE PHOENIX METRO THIS
EVENING...AND WINDS WILL MAINTAIN AN EASTERLY TRAJECTORY WITH CIGS
ABOVE 12K FT THROUGH SUNDAY MORNING. PROSPECTS FOR STORMS DIRECTLY
IMPACTING PHOENIX TERMINALS SUNDAY AFTERNOON ARE REMOTE AT
BEST...WITH ONLY TYPICAL WEST SFC WINDS DEVELOPING AFTER NOON.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NO AVIATION IMPACTS WITH ONLY PERIODIC HIGH CIRRUS CLOUDS THROUGH
SUNDAY EVENING. SFC WINDS WILL FAVOR A S/SW DIRECTION THROUGH THE
PERIOD...THOUGH PERIODS OF VARIABLE WINDS WILL BE COMMON SUNDAY
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...CB
AVIATION...MO
FIRE WEATHER...HIRSCH



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