Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 020414
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
914 PM MST MON JUN 1 2015

.SYNOPSIS...
LOW PRESSURE...THAT WILL BE MOVING INTO THE WESTERN STATES OVER THE
NEXT SEVERAL DAYS...IS EXPECTED TO BRING A SLOW COOLING TREND TO THE
REGION THROUGH THE REST OF THE WEEK...WITH MANY LOWER DESERT
LOCATIONS SEEING HIGHS BACK DOWN INTO THE 90S BY THE END OF THE WEEK.
THIS SAME LOW PRESSURE SYSTEM IS THEN EXPECTED TO PULL AT LEAST SOME
TROPICAL MOISTURE...AND BRING A SLIGHT CHANCE FOR SHOWERS AND
THUNDERSTORMS NORTHWARD INTO THE REGION BY THE END OF THE WEEK...AND
INTO THE UPCOMING WEEKEND.

&&

.DISCUSSION...
DRY WESTERLY FLOW AROUND AN ANTICYCLONE IN THE EASTERN PACIFIC
PREVAILS ACROSS THE DESERT SOUTHWEST THIS EVENING. LATEST TWC PWAT
AND LOW-LEVEL MIXING RATIOS WERE ANOMALOUSLY LOW THIS EVENING AND
THIS IS REFLECTED IN THE SURFACE DEWPOINTS WHICH HAVE GENERALLY BEEN
RUNNING IN THE 20S ACROSS THE LOWER DESERTS. MEANWHILE...LATEST IR
SATELLITE SHOWS A FEW PATCHES OF CIRRUS CURRENTLY SLIDING EASTWARD
ACROSS AZ. THIS WILL BE SHORT-LIVED AND CLEAR SKIES ARE EXPECTED
AFTER MIDNIGHT. CURRENT FORECAST IS IN GOOD SHAPE AND ONLY MINOR
ADJUSTMENTS TO THE SHORT-TERM TEMPERATURES AND DEWPOINTS WERE NEEDED.

&&

.DISCUSSION...
TONIGHT THROUGH THURSDAY... THE LATEST GLOBAL MODELS
SUITES CONTINUE THE IDEA OF EARLIER RUNS...WHICH HAVE TAKEN ENERGY
FROM A RATHER DEEP...AND COLD UPPER LOW CENTER THAT IS CURRENTLY OVER
THE GULF OF ALASKA...EASTWARD INTO THE WESTERN US...WHICH IS EXPECTED
TO ALLOW THE DEVELOPMENT OF A VERY DEEP (FOR JUNE) UPPER TROF THAT IS
FORECAST TO DROP SLOWLY SOUTHWARD ALONG THE WEST COAST THROUGH THE
REMAINDER OF THIS WEEK...WITH NAEFS STANDARDIZED ANOMALIES AOB -2.0SD
OFF THE SOUTHERN CA COAST BY FRI/SAT. THE MAIN IMPACT FOR OUR
CWA...AT LEAST THROUGH THURSDAY...IS TO BRING A GRADUAL COOLING TREND
TO THE REGION...WITH THE BEST-PERFORMING NUMERICAL GUIDANCE IS
BRINGING HIGHS BACK DOWN BELOW 100 AT MANY LOWER DESERT LOCATIONS BY
THURSDAY. ALONG WITH THE COOLER TEMPERATURES...STRONG WINDS ALOFT ARE
ALSO EXPECTED TO ENHANCE OUR TYPICAL AFTERNOON BREEZES A BIT...BUT
WIND SPEEDS ARE NOT EXPECTED TO COME ANYWHERE CLOSE TO ADVISORY
CRITERIA. OUTSIDE OF THE COOLER TEMPERATURES AND ENHANCED BREEZES...A
STILL-DRY AIRMASS IS EXPECTED TO KEEP DRY CONDITIONS AND MAINLY CLEAR
SKIES IN PLACE THROUGH THURSDAY.

FRIDAY THROUGH MONDAY... THERE STILL IS A GREAT DEAL OF UNCERTAINTY
IN THE FORECAST FOR THIS PERIOD. ALTHOUGH THE EURO...GFS...AND GEM
MODELS...AND A NUMBER OF THEIR ENSEMBLE MEMBERS ARE IN GOOD
AGREEMENT ON THE OVERALL LARGE-SCALE PATTERN OVER THE REGION...WHICH
MAINTAINS A DEEP UPPER-LEVEL TROF OVER SOUTHERN CA/AZ...THERE IS
STILL A GREAT DEAL OF DISAGREEMENT ON HOW THEY HANDLE MOISTURE
ASSOCIATED WITH TWO TROPICAL CYCLONES THAT HAVE NOW DEVELOPED IN THE
EASTERN PACIFIC. THE 1ST ONE...HURRICANE ANDRES...WHICH WAS A CAT-4
STORM THIS MORNING...LOCATED SEVERAL HUNDRED MILES SOUTHWEST OF THE
SOUTHERN TIP OF BAJA...NOW SLOWLY WEAKENING AND MOVING TO THE
NORTHWEST. ALTHOUGH THIS STORM IS EXPECTED TO CONTINUE TO MOVE OFF
THE THE NORTHWEST AND WEAKEN OVER THE NEXT FEW DAYS...THE GFS
CONTINUES TO PULL A FAIR BIT OF MOISTURE FROM THE REMAINS OF ANDRES
NE-WARD INTO THE SOUTHWEST US BY FRI/SAT...WITH PWATS IN THIS
MOISTURE PLUME RISING AS HIGH AS 1.50 INCHES OVER WESTERN AZ BY
MIDDAY FRIDAY. THE EURO...ON THE OTHER HAND...CONTINUES TO BE MUCH
DRIER...TAKING A MUCH WEAKER MOISTURE PLUME...WITH PWATS AOB 1.00
INCH INTO EASTERN AZ. GIVEN ALL THE UNCERTAINTY...HAVE DECIDED TO
JUST RAISE POPS A BIT FOR FRI/SAT...INTO THE SLIGHT CHANCE CATEGORY.

THE 2ND TROPICAL SYSTEM...BLANCA...WHICH IS NOW A RAPIDLY DEEPENING
TROPICAL STORM...LOCATED A FEW HUNDRED MILES SOUTH-SOUTHWEST OF
ZIHUATANEJO, MEXICO...IS FORECAST BY THE NHC TO CONTINUE TO RAPIDLY
DEEPEN...AND BECOME A MAJOR HURRICANE BY THU MORNING AS IT MOVES
NORTHWEST TOWARDS THE SOUTHERN TIP OF BAJA. THERE IS A POTENTIAL
THAT MOISTURE FROM THIS SYSTEM COULD AFFECT OUR REGION AS WELL BY
LATER IN THE WEEKEND OR EARLY NEXT WEEK...ESPECIALLY IF THE GFS IS
RIGHT. AT THIS POINT...WILL JUST MAINTAIN SOME SINGLE-DIGIT TO LOW
TEEN POPS FOR THE SUNDAY-MONDAY PERIOD FOR NOW...ALONG WITH NEAR TO
BELOW-NORMAL TEMPS.

&&

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

PERSISTENT WESTERLY FLOW WILL MEAN A LATE ONSET OF THE DOWNSLOPE FLOW
AT THE PHOENIX TERMINALS. BREEZY CONDITIONS ANTICIPATED AGAIN TUESDAY
AFTERNOON AREA-WIDE...WITH SUSTAINED WINDS OF 15-20 KT LIKELY AGAIN AT
KIPL/KBLH AND POSSIBLE AT KPHX.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

THURSDAY THROUGH MONDAY...TEMPERATURES WILL CONTINUE TO SLOWLY
DECLINE THE REST OF THE WEEK AND INTO THE WEEKEND...EVENTUALLY
DIPPING A BIT BELOW NORMAL...DUE TO TROUGHING DEEPENING OVER THE
WEST COAST. HUMIDITIES WILL BE QUITE LOW THURSDAY BEFORE INCREASING
LATE IN THE WEEK AND OVER THE WEEKEND. THE AMOUNT OF THE INCREASE
REMAINS TO BE SEEN. THERE IS A POSSIBILITY THAT SOME MOISTURE WILL
BE STRIPPED OFF OF A COUPLE OF TROPICAL SYSTEMS...CURRENTLY WELL OFF
THE SOUTHWEST COAST OF MEXICO...AND WORK ITS WAY INTO THE DESERT
SOUTHWEST. IN THE MOST AGGRESSIVE MODEL SCENARIO...NORTHERN AND
SOUTHEASTERN ARIZONA WOULD SEE THE BRUNT OF PRECIPITATION. STILL A
LOT OF UNCERTAINTY ON THE WHAT/WHEN/WHERE PARAMETERS FOR THE FRIDAY-
MONDAY TIME FRAME.


&&

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

&&

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

$$

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

DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...PERCHA
AVIATION...HIRSCH
FIRE WEATHER...AJ


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