Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 292159
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
300 PM MST FRI AUG 29 2014


.SYNOPSIS...
MOSTLY CLEAR SKIES WITH LOWER HUMIDITY WILL CONTINUE TO PROVIDE
ABOVE NORMAL AFTERNOON TEMPERATURES THROUGH THE MIDDLE OF NEXT
WEEK...HOTTEST TEMPERATURES WILL BE SATURDAY. A GRADUAL UPTREND IN
STORM CHANCES IS EXPECTED TO BEGIN OVER ARIZONA WEDNESDAY WITH
SLIGHT CHANCES EXPANDING TO THE LOWER DESERTS BY NEXT FRIDAY.

&&

.DISCUSSION...
REST OF TODAY THROUGH TUESDAY...
TEMPERATURES IN PORTIONS OF SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA RUNNING SLIGHTLY HOTTER THAN FORECAST THIS
AFTERNOON...AND WILL PROBABLY REACH EXCESSIVE HEAT CRITERIA. WITH
NO CHANGE EXPECTED SATURDAY...AN EXCESSIVE HEAT WARNING HAS BEEN
ISSUED FOR SATURDAY OVER SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA.
TEMPERATURES ARE NOT QUITE AS HOT OVER THE LOWER ELEVATIONS OF
SOUTH-CENTRAL ARIZONA BUT ARE RUNNING AT LEAST A FEW DEGREES ABOVE
NORMAL. EXPECT VERY SIMILAR TEMPERATURES FOR SATURDAY. MODELS DEPICT
A LITTLE BIT OF COOLING SUNDAY AS THE RIDGE AXIS IS NUDGED
SOUTHWARD DUE TO A TROUGH PASSING TO THE NORTH. THIS SHOULD PRECLUDE
THE NEED FOR A HEAT WARNING ON SUNDAY. ALSO...DEW POINTS MAY BE
HIGHER AS BOTH THE GFS AND NAM DEPICT A MOISTURE SEEP FROM
SONORA/SEA OF CORTEZ. THE NAM IS FASTER WITH THE ARRIVAL AND
SLIGHTLY JUICIER. NOT ENOUGH MOISTURE TO GET STORMS TO FORM THOUGH.
EARLY NEXT WEEK...AN ANTICYCLONE WITHIN A VERY BROAD REGION OF
SUBTROPICAL HIGH PRESSURE SLOWLY MIGRATES NORTHWARD. NOT MUCH
DISCERNIBLE IMPACT. FORTUNATELY...MODELS AGREE THAT THE MINOR
COOLING FROM SUNDAY INTO MONDAY IS NOT REVERSED. NOT ENOUGH MOISTURE
FOR STORM CHANCES OVER OUR AREA THROUGH TUESDAY. SOUTHWESTERLY FLOW
ALOFT ALSO MAKES IT UNLIKELY FOR STORMS TO GET ADVECTED INTO OUR CWA
FROM SOUTHEAST ARIZONA. ANTICIPATE TEMPS 2-3 DEGREES ABOVE NORMAL
MONDAY AND TUESDAY.

WEDNESDAY THROUGH FRIDAY...
DURING THE LATTER HALF OF NEXT WEEK...MODELS ARE IN PRETTY GOOD
AGREEMENT THAT AN ANTICYCLONE CENTERED NEAR THE MEXICO BORDER WILL
BE ABSORBED INTO A MUCH LARGER ANTICYCLONE CENTERED OVER THE
SOUTHEAST STATES. WITH TIME...FLOW BECOME MORE SOUTH AND
SOUTHEASTERLY WHICH ALLOWS BETTER MOISTURE TO RETURN TO ARIZONA.
THUS THERE IS A GRADUAL UPTREND IN POPS. THERE ARE SOME DIFFERENCES
IN THE DETAILS THOUGH AS THE GFS IS LESS GENEROUS WITH THE MOISTURE
THAN THE ECMWF. THIS APPEARS TO BE RELATED TO HOW THEY HANDLE AN
INVERTED TROUGH. THE GFS KEEPS IT FURTHER SOUTH THAN THE ECMWF. BOTH
HAVE BEEN FAIRLY CONSISTENT IN THEIR RESPECTIVE SOLUTIONS. NUDGED
PREVIOUS POP NUMBERS UPWARD SO THAT THERE IS MORE AREA COVERED BY
SLIGHT CHANCE IN THE WED-FRI TIME FRAME...ESPECIALLY FRIDAY.

&&

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

STRONG HIGH PRESSURE AND WEAK SFC PRESSURE GRADIENTS WILL KEEP SKIES
MAINLY CLEAR THROUGH THE TAF PERIOD AND WINDS MOSTLY ON THE LIGHT
SIDE...MAINLY FOLLOWING TYPICAL DIURNAL TRENDS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
AFTER A DRY PERIOD ON MONDAY AND TUESDAY...INCREASING SOUTHERLY FLOW
ALOFT WILL ALLOW MOISTURE LEVELS TO SLOWLY INCREASE THROUGH THE
REMAINDER OF THE WORKWEEK. ISOLATED SHOWER/THUNDERSTORM ACTIVITY
OVER THE HIGHER TERRAIN EAST OF PHOENIX IS EXPECTED TO SPREAD
WESTWARD INTO THE LOWER DESERTS OF SOUTH-CENTRAL AZ BY FRIDAY
AFTERNOON. AFTERNOON HUMIDITY VALUES...WHICH WILL BE FALLING INTO
THE TEENS ON MONDAY AND TUESDAY...WITH FAIR TO GOOD OVERNIGHT
RECOVERIES...ARE EXPECTED TO RISE INTO THE 20S ON FRIDAY...WITH GOOD
TO EXCELLENT OVERNIGHT RECOVERIES. TEMPERATURES DURING THE ENTIRE
FORECAST PERIOD WILL REMAIN NEAR...TO SLIGHTLY ABOVE NORMAL.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...AJ
AVIATION...PERCHA
FIRE WEATHER...PERCHA





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