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000
FXUS65 KPSR 211704
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1005 AM MST TUE MAY 21 2013

.SYNOPSIS...
HIGH PRESSURE ACROSS THE REGION WILL BRING CONTINUED DRY WEATHER AND
ABOVE NORMAL TEMPERATURES THROUGH MID WEEK. CLEAR SKIES AND SOMEWHAT
BREEZY AFTERNOONS ARE EXPECTED NEARLY EVERY DAY THROUGH THE WEEKEND.
A DEEP LOW PRESSURE SYSTEM WILL MOVE SOUTHEAST INTO THE GREAT BASIN
BY LATE WEEK ALLOWING A SLIGHT COOLING TREND. THE DRY CONDITIONS
WILL CONTINUE THROUGH THE COMING WEEKEND WHILE TEMPERATURES FALL
BACK TO AROUND SEASONAL NORMALS STARTING LATE THIS WEEK.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A REX PATTERN OVER NORTH AMERICA WITH A
NARROW HIGH AMPLITUDE RIDGE OVER SOUTHERN CALIFORNIA/ARIZONA
EXTENDING NORTHEASTWARD INTO CANADA. IMMEDIATELY DOWNSTREAM IS AN
UPPER LOW CENTERED OVER THE NORTHERN PLAINS AND UPPER MIDWEST AND
IMMEDIATELY UPSTREAM OF THE RIDGE IS A DEEP UPPER LOW CENTERED JUST
OFF THE PACIFIC NORTHWEST COAST. THE RIDGE AXIS WILL MOVE EASTWARD
INTO ARIZONA TODAY BEFORE SHIFTING OVER THE ROCKIES BY WEDNESDAY
MORNING. THE RIDGING COUPLED WITH DRIER AIR WILL HELP WITH SOME
WARMING TODAY...MORE NOTICEABLY OVER SOUTHEAST CALIFORNIA. CIRRUS
WILL INCREASE TODAY AS SOUTHWESTERLY FLOW ALOFT BEGINS TO MOVE IN.
OTHER THAN SOME MINOR TWEAKS TO TODAYS DEW POINT/RH GRIDS...NO
CHANGES AT THIS TIME.

&&

.PREVIOUS DISCUSSION ISSUED 301 AM...
AN UPPER LEVEL RIDGE AXIS WILL MOVE THROUGH THE REGION TODAY WITH
SOME SLIGHT WARMING TAKING PLACE. THE STRONGEST BOUNDARY LAYER
WARMING WILL SOMEWHAT LAG BEHIND THE RIDGE AXIS WITH HIGHS TOPPING
100 ACROSS OUR WESTERN ZONES TODAY AND THEN ACROSS SOUTH-CENTRAL
ARIZONA ON WEDNESDAY. WILL ALSO SEE A SLUG OF MOISTURE BETWEEN
300-400MB MOVE THROUGH TODAY WHICH SHOULD BRING A FEW HOURS OF
BROKEN CIRRUS...THOUGH NOT EXPECTING CLOUDS TO HAVE ANY IMPACT ON
AFTERNOON HIGHS. COLUMN MOISTURE WILL THEN BE SCARCE FOR WEDNESDAY
AND THURSDAY RESULTING IN CLEAR SKIES.

AN UPPER LEVEL OMEGA BLOCKING PATTERN TAKES HOLD STARTING WEDNESDAY
WITH A DEEP CLOSED LOW MOVING INTO THE PACIFIC NORTHWEST AND
STALLING...WHILE A HIGH AMPLITUDE RIDGE SETS UP OVER THE PLAINS
STATES INTO SOUTH-CENTRAL CANADA. THIS BLOCKING PATTERN WILL BRING
AN EXTENDED PERIOD THE DRY AND QUIET WEATHER TO THE DESERT
SOUTHWEST. THE CLOSED LOW TO THE NORTH WILL HAVE A SLIGHT IMPACT
ACROSS THE REGION...MORE SO ACROSS OUR WESTERN ZONES IN THE EFFECT
OF COOLER TEMPERATURES. STARTING THURSDAY AND LASTING AT LEAST
THROUGH THE WEEKEND...THE REGION WILL BE UNDER THE INFLUENCE OF DRY
SOUTHWESTERLY FLOW ALOFT WITH VERY LITTLE CHANGE IN AIRMASS
TEMPERATURES. THE COOLDOWN STARTING THURSDAY WILL BE MORE PRONOUNCED
ACROSS SOUTHEAST CALIFORNIA WITH TEMPERATURES A FEW DEGREES BELOW
NORMAL...AND THESE COOLER TEMPERATURES WILL LIKELY PERSIST INTO
EARLY NEXT WEEK. FARTHER AWAY FROM THE CLOSED UPPER
LOW...SOUTH-CENTRAL ARIZONA WILL BE SLIGHTLY WARMER WITH
TEMPERATURES RIGHT AROUND SEASONAL NORMALS FOR THE SAME PERIOD. THE
REGION WILL ALSO BE IN FOR SEVERAL DAYS OF BREEZY
CONDITIONS...MAINLY DURING THE AFTERNOON HOURS WITH THE POTENTIAL TO
MIX UP TO 700MB.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...KSDL...
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA...INCLUDING KIPL AND KBLH...

THROUGH 19Z TUE...CLEAR SKIES. LIGHT WIND. FROM 19Z TUE TO 02Z WED...
CLEAR SKIES. WEST WIND 5 TO 10 KTS...OCCASIONAL 15 KTS LATE AFTN.


AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
A LARGE PACIFIC LOW PRESSURE SYSTEM WILL MOVE INTO THE WESTERN
STATES NORTH OF AZ. DRY WEATHER WILL CONTINUE OVER THE AREA...
HOWEVER GUSTY AFTERNOON SOUTHWEST WINDS ARE EXPECTED EACH DAY.
SINGLE DIGIT MINIMUM HUMIDITIES WILL CONTINUE. OVERNIGHT RECOVERY
WILL BE POOR OVER SOUTH-CENTRAL ARIZONA AND POOR TO FAIR OVER
SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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DISCUSSION...AJ
PREVIOUS DISCUSSION...KUHLMAN
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ/AJ