Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 021644
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
944 AM MST MON MAY 2 2016

.SYNOPSIS...
LOW PRESSURE WILL MAKE A SLOW EXIT TO THE EAST ACROSS NORTHERN AZ
TODAY...KEEPING THE FOCUS OF ANY LINGERING PRECIP ACTIVITY WELL NORTH
OF OUR FORECAST AREA. HIGH PRESSURE MOVING IN FROM THE WEST WILL
BUILD OVER THE DESERT SOUTHWEST THROUGH THURSDAY...RESULTING IN
MOSTLY CLEAR SKIES AND A STRONG WARMING TREND. ANOTHER PACIFIC
WEATHER SYSTEM WILL BEGIN TO MOVE INTO THE AREA FRIDAY AND FOR THE
COMING WEEKEND...BRINGING MUCH COOLER TEMPERATURES...BREEZY
CONDITIONS AND A SLIGHT CHANCE OF SHOWERS.

&&

.DISCUSSION...
MINOR ADJUSTMENTS TO THE FORECAST THIS MORNING TO ACCOUNT FOR VARIOUS
TRENDS INCLUDING CLEAR SKY AND HIGHER HUMIDITY VALUES. TEMPERATURES
ARE PRETTY MUCH ON TRACK TO HIT FORECAST HIGHS THIS AFTERNOON. WE ARE
SEEING A PUSH OF EASTERLY WINDS ACROSS MARICOPA AND PINAL COUNTIES
THIS MORNING AND THAT SHOULD SUBSIDE BY EARLY AFTERNOON.

LAST SHORT WAVE IS ABOUT OVER LAS VEGAS THIS MORNING AND IT WILL MOVE
ACROSS NORTHERN ARIZONA TODAY. A MORE LAMINAR FLOW OVER SOUTHERN
CALIFORNIA AND SOUTHERN ARIZONA...WITH SOME MINOR WAA...WILL KEEP
PRECIPITATION CHANCES QUITE LOW. MOST OF THE CAMS ARE GENERATING A
LITTLE ACTIVITY OVER JOSHUA TREE NP AND WE WILL MAINTAIN A SLIGHT
CHANCE FOR RAIN THERE.

LOOKING AHEAD...MESSAGE OF THE DAY WILL INCLUDE WARMING TEMPERATURES
WITH THE FIRST 100 POSSIBLE FOR PHOENIX AND YUMA ON WEDNESDAY /BUT
NOT GUARANTEED AND NOT FORECAST AT THIS TIME/...STRONG WINDS THURSDAY
LIKELY GENERATING AREAS OF BLOWING DUST AND POSSIBLE DANGEROUS FIRE
WEATHER CONDITIONS...THEN THE COOL DOWN FOR THE WEEKEND WITH PERHAPS
A FEW SHOWERS. MORE DETAILS BELOW AND UPDATES THIS AFTERNOON.

PREVIOUS DISCUSSION...
HIGH-AMPLITUDE HIGH PRESSURE WILL TAKE A FEW-DAY HOLD OVER THE
INTERMOUNTAIN WEST ALLOWING DAYTIME TEMPERATURES TO TAKE ANOTHER RUN
AT THEIR WARMEST READINGS OF THE YEAR SO FAR BY MIDWEEK. 500MB
HEIGHTS STILL PROGGED INTO THE 576-582DM RANGE AND 850MB AFTN
TEMPERATURE QUICKLY HEAD NORTH OF 20 TO 25C AFTER MONDAY. MID TO
UPPER 90 DEGREE READINGS ARE ANTICIPATED FOR THE LOWER DESERT
ELEVATIONS TUESDAY AND WEDNESDAY. WEDNESDAY STILL PINNED TO BE THE
WARMEST DAY OF THE WEEK AND QUITE POSSIBLY THE YEAR AS THE RIDGE AXIS
BEGINS TO SHIFT TO OUR EAST AS STRONG SOUTHERLY FLOW DEVELOPS INTO
THE AREA ENHANCING WAA FROM THE SUBTROPICS. CONSENSUS GUIDANCE
SUPPORTING UPPER 90S FOR MANY OF THE DESERT SITES...WITH 100S STILL
POSSIBLE FOR THE WARMEST LOCALES SUCH AS TACNA AND EL CENTRO. THE
FIRST 100F FOR PHOENIX HAS POPPED INTO SOME OF THE LATEST GRIDDED
GUIDANCE WEDNESDAY...BUT ARE FROM MODEL PERFORMERS NOT TYPICAL OF
THOSE THAT DO WELL WITH HIGH PRESSURE PATTERNS.

THURSDAY THROUGH NEXT WEEKEND...
MODEL AGREEMENT AND TRENDS...BOTH IN THE DETERMINISTIC AND ENSEMBLE
SOLUTIONS...HAVE REMAINED IN EXCELLENT AGREEMENT OVER THE PAST
SEVERAL DAYS IN ADVERTISING A DEEP PACIFIC TROUGH MOVING INTO THE
SOUTHWEST BY THE LATE WEEK/EARLY WEEKEND. TROUGHING REACHES AS FAR
SOUTH AS THE NORTHERN BAJA PENINSULA AND MAINTAINS ITS COOL
TEMPERATURE PROFILE BY THURSDAY. DAYTIME TEMPERATURES WILL BEGIN TO
COOL ACROSS THE WESTERN FORECAST ZONES AS STRONG SOUTHERLY LOW-LEVEL
WINDS DEVELOP INTO THE REGION. JET-LEVEL WINDS BEGIN TO PUSH 100KTS
THURSDAY AFTERNOON...WITH LL WINDS AT 700MB AND 850MB ENCROACHING 35
TO 45 KTS. WINDS FORECAST TO BE AT THEIR STRONGEST ON THURSDAY...WITH
AREA WIDE SUSTAINED SFC SPEEDS PUSHING 25 MPH AND GUSTS 35 MPH OR
GREATER. WITH THE WINDS COMES THE THREAT FOR DUST...SO INCLUDED
MENTION OF BLOWING DUST IN THE GRIDS FOR BOTH WEDNESDAY AND THURSDAY
AS THE SYSTEM WINDS RAMP UP INTO THE AREA. THE ONE FORECAST ELEMENT
THAT REMAINS A BIT OF A UNKNOWN QUANTITY WILL BE THE MOISTURE...AS
PWAT FIELDS APPEAR TO STRUGGLE BREAKING PAST HALF INCH READINGS.
QPF/PRECIP PLOTS FROM THE DETERMINISTIC AS WELL AS THE GEFS
REFORECAST ARE NOT OVERLY EXCITED ABOUT ANY PERIODS OF PERSISTENT
RAINFALL INTO THE AREA ON THIS SYSTEM SWINGS IN OFF THE PACIFIC AND
SETTLES OVER THE AREA BY FRIDAY.

A WELCOME COOL-DOWN WILL RESULT FOR THE SOUTHWEST AS 500MB
TEMPERATURES BEGIN TO RUN COOLER THAN -20C ACROSS THE AREA...WITH
DAYTIME HIGHS DIPPING INTO THE UPPER 70S AND LOW 80S. AS WITH
PREVIOUS SYSTEMS...THE UPPER LOW FEATURE WILL TAKE UP RESIDENCE OVER
THE WEST INTO THE WEEKEND AND POSSIBLY VERY EARLY NEXT WEEK...AS IT
BECOMES THE WESTERN END OF A CONUS WIDE OMEGA BLOCK. VORTICITY PLOTS
INDICATE IT COULD BEGIN TO LOBE OUT...ALLOWING FOR ON AND OFF ROUNDS
OF BREEZINESS AND SOME PRECIP CHANCES TO OCCUR THROUGHOUT THE
SOUTHWEST STATES.

&&

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

DRY WESTERLY FLOW ALOFT WILL RESULT IN MOSTLY CLEAR SKIES THROUGH
23Z MON. LIGHT AND VARIABLE WINDS UNDER 7 KNOTS THROUGH 23ZZ MON.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

WEDNESDAY AND THURSDAY...

A HIGH PRESSURE SYSTEM WILL CONTINUE OVER THE REGION ON WEDNESDAY...
HOWEVER ANOTHER PACIFIC COLD FRONT WILL APPROACH THE WEST COAST
WEDNESDAY AFTERNOON...THEN MOVE THROUGH THE REGION THURSDAY. AS A
RESULT...BREEZY SOUTHWEST WINDS WILL DEVELOP WEDNESDAY AFTERNOON AND
EVENING...BECOMING VERY WINDY THURSDAY. SINCE RELATIVE HUMIDITIES
THURSDAY WILL RANGE FROM 10 TO 15 PERCENT...RED FLAG CONDITIONS MAY
BE REACHED ON THE SOUTHWEST AND SOUTH CENTRAL AZ DESERTS THURSDAY
AFTERNOON.

FRIDAY THROUGH SUNDAY...

AFTER THE COLD FRONTAL PASSAGE THURSDAY...A COOL AND RELATIVELY
MOIST AIRMASS WILL SETTLE OVER THE REGION THIS PERIOD. BREEZY WEST
WINDS MAY DEVELOP FRIDAY AFTERNOON...BUT BECOME MUCH LIGHTER
SATURDAY AND SUNDAY. MINIMUM RELATIVE HUMIDITIES WILL INCREASE AREA-
WIDE INTO THE 17 TO 24 PERCENT RANGE. A SLIGHT CHANCE OF SHOWERS...
UNDER A RELATIVELY COOL AND MOIST AIRMASS...WILL DEVELOP FRIDAY AND
SATURDAY.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED.

&&

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

$$

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

DISCUSSION...INIGUEZ/NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ


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