Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 260327
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
825 PM MST TUE NOV 25 2014

.SYNOPSIS...
DRY AIR WILL CONTINUE TO OVERSPREAD THE AREA...RESULTING IN MOSTLY
CLEAR SKIES AND TEMPERATURES NEAR NORMAL THROUGH WEDNESDAY.
AFTERNOON TEMPERATURES WILL PEAK IN THE UPPER 70S/LOWER 80S TOWARD
THE END OF THE WEEK AS A STRENGTHENING HIGH PRESSURE RIDGE POSITIONS
ITSELF OVER THE DESERT SOUTHWEST.

&&

.DISCUSSION...
STRONG RIDGING WAS BUILDING EAST INTO THE FORECAST AREA REGION THIS
EVENING PER WV IMAGERY. CLEAR SKIES AND A WEAK PRESSURE GRADIENT
PROVIDING LIGHT WINDS WERE ALLOWING TEMPERATURES TO FALL FAIRLY
QUICKLY IN A DRY ENVIRONMENT. FOR THE MOST PART...THE FORECAST HAD
ACCOUNTED FOR THIS AND ONLY MADE MINOR 1F-3F HOURLY AND FORECAST LOW
TEMPERATURES ADJUSTMENTS BASED ON CURRENT TRENDS. OTHERWISE...NO
MAJOR CHANGES WERE NEEDED IN THE EVENING UPDATE.

&&

.PREVIOUS DISCUSSION...
/205 PM MST TUE NOV 25 2014/
LATEST STREAMLINE ANALYSIS SHOWS A BROAD ANTICYCLONE ACROSS THE
EASTERN PACIFIC PRODUCING A DRY SUBSIDENT NORTHWESTERLY FLOW ACROSS
THE DESERT SOUTHWEST. STANDARDIZED ANOMALIES ASSOCIATED WITH THE
RIDGE OFF THE WEST COAST ARE ON THE ORDER OF 1 TO 3 ABOVE THE MEAN.
MEANWHILE...SURFACE DEWPOINTS HAVE DROPPED INTO THE SINGLE DIGITS
AND EVEN BELOW ZERO IN SOME SPOTS ACROSS THE PHOENIX AREA.

TONIGHT...LIGHT WINDS AND CLEAR SKIES WILL BEGET OPTIMAL RADIATIONAL
COOLING CONDITIONS. BELOW NORMAL TEMPERATURES ARE EXPECTED WITH
READINGS AS LOW AS THE UPPER 30S ACROSS THE SOUTHEAST VALLEY AND
EVEN A FEW DEGREES COOLER INTO PINAL COUNTY. FORECAST WAS WEIGHTED
TOWARDS A CONSENSUS OF THE BIAS-CORRECTED MOS VALUES...WHICH
TRADITIONALLY DOES QUITE WELL IN THESE SCENARIOS.

MODELS REMAIN IN EXCELLENT AGREEMENT DEPICTING A WARMING TREND
THROUGH THANKSGIVING AS THE RIDGE SLIDES EASTWARD. ECMWF HAS BEEN A
TOP PERFORMER RECENTLY FOR MAX TEMPERATURE AND THE FORECAST HIGH IN
PHOENIX WAS RAISED TO 82 DEGREES FOR THANKSGIVING...A FEW DEGREES
SHY OF THE RECORD OF 86 DEGREES LAST SET IN 1950.

THE VAST MAJORITY OF THE UPCOMING FORECAST WILL FEATURE DRY WEATHER
WITH ABOVE NORMAL TEMPERATURES. LOOKING AHEAD FOR MID
WEEK...THANKSGIVING...AND INTO THE WEEKEND...A RIDGE OFF THE WEST
COAST WILL GRADUALLY MOVE INLAND AND POSITION ITSELF OVER ARIZONA
THURSDAY/FRIDAY. THIS WILL RESULT IN GRADUALLY INCREASING
TEMPERATURES...PEAKING AROUND 80 ACROSS THE LOWER DESERTS THURSDAY
AND FRIDAY...POSSIBLY SATURDAY AS WELL AS HEIGHTS AND 925MB TEMPS
REMAIN VIRTUALLY UNCHANGED DURING THIS PERIOD. OVERALL VERY QUIET
WEATHER WITH NO CHANCE OF PRECIP.

ATTENTION TURNS TOWARD A LARGE UPPER LOW WHICH WILL MOVE THROUGH
NORTHERN CALIFORNIA ON SUNDAY AND INTO NEVADA/UTAH/ARIZONA EARLY
NEXT WEEK. OPERATIONAL MODELS AND ENSEMBLES ARE BEGINNING TO
CONVERGE ON A SOLUTION OF PRECIP DEVELOPING AT SOME POINT MONDAY
ACROSS SOUTHEAST CALIFORNIA AS MOISTURE CONVERGENCE AND ISENTROPIC
ASCENT STRENGTHENS EAST OF THE COASTAL MOUNTAINS. TODAYS 00Z GFS IS
A BIT FASTER AND MORE PROGRESSIVE WITH THE TROUGH COMPARED TO THE
ECMWF. ENSEMBLES SEEM TO FAVOR A SLIGHTLY SLOWER ARRIVAL PER THE
ECMWF SOLUTION. I INTRODUCED 20-30 POPS ACROSS PORTIONS OF THE AREA
AS EARLY AS MONDAY ACROSS SOUTHEAST CALIFORNIA...AND ACROSS ARIZONA
MONDAY EVENING/TUESDAY. BIGGEST UNCERTAINTY AT THIS POINT IS TIMING
WHEN THE PRECIP WILL ARRIVE. COULD ALSO SEE SNOW LEVELS FALL QUITE A
BIT BEHIND THE LOW ALTHOUGH AT THIS POINT IMPACTS APPEAR TO BE
MINIMAL IN OUR HIGHER TERRAIN LOCALES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...AND
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND
KBLH...
NO SIGNIFICANT AVIATION CONCERNS THROUGH WEDNESDAY EVENING UNDER
CLEAR SKIES. SLANTWISE VISIBILITIES COULD BE ONCE AGAIN BE REDUCED
BY SMOKE DURING THE LATE NIGHT/EARLY MORNING HOURS WEST OF KPHX.
OTHERWISE...WINDS WILL BE UNUSUALLY LIGHT UNDER 8 KT...AND IN MANY
CASES CALM OR VARIABLE FOR PROLONGED PERIODS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
STRONG HIGH PRESSURE WILL AFFECT THE DESERT SOUTHWEST THURSDAY AND
FRIDAY...FOR WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. HIGH
TEMPERATURES BOTH DAYS WILL CLIMB INTO THE LOW 80S OVER THE WARMEST
LOWER DESERTS.A SUBTLE COOLING TREND IS ANTICIPATED OVER THE WEEKEND
AS THE HIGH GRADUALLY WEAKENS...BUT HIGH TEMPERATURES WILL REMAIN
WELL ABOVE SEASONAL NORMALS. HUMIDITY VALUES WILL BE LOW THROUGH
SATURDAY...WITH MOST OF THE DESERTS MOSTLY IN THE TEENS. HUMIDITY
LEVELS WILL CLIMB SUNDAY INTO MONDAY AS A PACIFIC LOW PRESSURE
SYSTEM STARTS TO MOVE INLAND AND INTO THE AREA FROM THE WEST. BY
MONDAY...EXPECT A SLIGHT CHANCE OF SHOWERS FROM THE CENTRAL ARIZONA
DESERTS WESTWARD. OVERNIGHT RECOVERIES WILL BE FAIR TO GOOD...SLOWLY
IMPROVING EACH NIGHT WITH MOST OF THE DESERTS REACHING BETWEEN 40
AND 50 PERCENT OVER THE WEEKEND. WINDS WILL BE ON THE LIGHT SIDE
EACH DAY THROUGH SUNDAY WITH ONLY MINOR AFTERNOON GUSTINESS.
INCREASED SOUTHERLY TO SOUTHWESTERLY BREEZINESS IS EXPECTED MONDAY
AHEAD OF THE APPROACHING WEATHER SYSTEM.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO/HIRSCH/LEINS
AVIATION...MO
FIRE WEATHER...CB





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