Weather Service Report


426 
FXUS65 KPSR 292153
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
253 PM MST FRI APR 29 2016

.UPDATE...UPDATED FIRE WEATHER DISCUSSION. 

.SYNOPSIS...
DRY NORTHWEST FLOW ALOFT WILL INCREASE OVER THE REGION THROUGH
SATURDAY. WARMER AFTERNOON TEMPERATURES ARE ALSO FORECAST.
HOWEVER...ANOTHER PACIFIC LOW PRESSURE SYSTEM IS EXPECTED TO MOVE
INTO THE REGION SATURDAY NIGHT AND SUNDAY...DEVELOPING BREEZY
CONDITIONS AND A THREAT FOR SHOWERS AND THUNDERSTORMS. THE BEST
CHANCE OF PRECIPITATION WILL OCCUR OVER THE SOUTH CENTRAL ARIZONA
DESERTS AND MOUNTAINS...MAINLY IN THE VICINITY OF PHOENIX. CLEARING
IS EXPECTED SUNDAY NIGHT...WITH HIGH PRESSURE AND MUCH WARMER
WEATHER NEXT WEEK.
 
&&

.DISCUSSION...
UPPER LEVEL LOW PRESSURE SYSTEM CONTINUED TO PUSH OFF TOWARDS THE
NORTHEAST THIS AFTERNOON WITH THE LOW CENTER MOVING EAST/NORTHEAST
OF THE FOUR CORNERS AND INTO SERN COLORADO. DRY SUBSIDENT AND
SLIGHTLY CYCLONIC NORTHWEST FLOW ALOFT WAS OVERSPREADING THE
DESERTS...ALLOWING FOR SOME THINNING OF THE THICKER MID CLOUD DECKS
THAT WERE IN PLACE THIS MORNING ACROSS SOUTH CENTRAL ARIZONA. RADAR
AT 2 PM SHOWED JUST A FEW LIGHT SHOWERS OVER HIGHER TERRAIN
NORTHEAST OF PHOENIX...WITH HIGH BASED CUMULUS OVER THE LOWER
CENTRAL DESERTS. TEMPERATURES EARLY THIS AFTERNOON WERE RUNNING 3-8
DEGREES AHEAD OF YESTERDAY AS SOME OF THE WARM AIR ALOFT WAS
TRANSLATING TO THE SURFACE. STILL...HIGHS TODAY WILL STAY BELOW
SEASONAL NORMALS...ONLY RISING INTO THE LOW 80S OVER THE GREATER
PHOENIX AREA.

FAST ON THE HEELS OF THE CURRENTLY EXITING LOW PRESSURE SYSTEM WILL
BE ANOTHER PACIFIC LOW MOVING IN FROM THE NORTHWEST DURING THE DAY
ON SATURDAY. MODEL GUIDANCE...INCLUDING OPERATIONAL RUNS OF THE
NAM/GFS/ECMWF AS WELL AS GEFS ENSEMBLE GUIDANCE...REMAINS CONSISTENT
IN THE TIMING AND TRACK OF THIS NEXT LOW...AND CONFIDENCE IN THE
FORECAST IS HIGH FOR BOTH PRECIP AND AN EXPECTED COOL DOWN. PROGS
MOVE THE UPPER LOW CENTER INTO FAR SRN NV AND FAR WCNTRL ARIZONA BY
SATURDAY AFTERNOON...AND THE BEST QG FORCING APPEARS TO MOVE INTO
SOUTHERN ARIZONA DURING THE DAY SATURDAY BEFORE THE DEEPER MOISTURE
ARRIVES. AS SUCH...WE HAVE POPS STARTING UP SATURDAY AFTERNOON BUT
MAINLY SLIGHT CHANCES OVER SERN CA AS WELL AS NORTHERN PORTIONS OF
LA PAZ AND MARICOPA COUNTIES. CANNOT RULE OUT A THUNDERSTORM
DEVELOPING SATURDAY AFTERNOON AS LIFTED INDICES DROP TO AROUND ZERO.
OVERNIGHT SATURDAY NIGHT AS THE UPPER LOW MOVES ACROSS SOUTH CENTRAL
ARIZONA...MAIN FORCING SHIFTS INTO THE EASTERN PORTION OF THE STATE
AND POPS ACROSS SOUTH CENTRAL AZ RISE INTO THE 20-30 PERCENT BALL
PARK...WITH SLIGHT CHANCES LINGERING FURTHER TO THE WEST. WIND
SHOULD NOT BE AS MUCH OF AN ISSUE WITH THIS SYSTEM AS WITH SOME OF
THE EARLIER ONES...BUT ONCE AGAIN FAVORED AREAS IN IMPERIAL
COUNTY...MAINLY FROM THE IMPERIAL VALLEY SOUTHWESTWARD...COULD REACH
TO NEAR WIND ADVISORY CRITERIA ON SATURDAY AS THE LOW APPROACHES.
FOR NOW WE WILL HIGHLIGHT THIS THREAT VIA SOCIAL MEDIA INSTEAD OF A
WIND ADVISORY. 

ON SUNDAY THE MAIN UPPER LOW SHIFTS EAST AND INTO NEW MEXICO...AND
DYNAMICS/Q CONVERGENCE SHIFT EAST WITH THE UPPER LOW...AND JET
DYNAMICS ALSO DECREASE MARKEDLY AS THE UPPER JET AXIS SHIFTS OFF TO
THE SOUTHEAST OF PHOENIX. SO THE QG FORCING DECREASES BUT
THERMODYNAMIC EFFECTS INCREASE AS COOL AIR ALOFT AND LOWER LEVEL
MOISTURE SPREAD INTO THE CENTRAL DESERTS. AS SUCH WE HAVE A 20-30
PERCENT CHANCE OF SHOWERS OR THUNDERSTORMS OVER SOUTH CENTRAL AZ
SUNDAY...WITH A LINGERING 10 PERCENT CHANCE OVER THE WESTERN DESERTS
INTO SERN CA. WE WILL SEE HIGH TEMPS COOL DOWN TO NEAR 80 OR INTO
THE UPPER 70S OVER SOUTH CENTRAL AZ...WITH HIGHS INTO THE MID 80S
OVER THE WARMER WESTERN DESERTS.

SUNDAY NIGHT INTO MONDAY...UPPER LOW IS FORECAST TO CONTINUE TO PUSH
OFF TO THE NORTHEAST AS RIDGING ALOFT BUILDS ALONG THE SRN CA COAST.
DRIER MORE SUBSIDENT WEST/NORTHWEST FLOW ALOFT SPREADS ACROSS THE
AREA FOR MOSTLY SUNNY SKIES ALONG WITH WARMER HIGH TEMPERATURES.
HIGHS WILL CLIMB INTO THE MID 80S TO AROUND 90 MONDAY. EXPECT A DRY
DAY ALTHOUGH THERE MAY BE ENOUGH LINGERING MOISTURE TO ALLOW FOR A
SLIGHT CHANCE OF A SHOWER OR AFTERNOON STORM OVER THE HIGHER TERRAIN
EAST OF GLOBE.

TUESDAY THROUGH FRIDAY...

A HIGH PRESSURE SYSTEM WILL BUILD INTO THE REGION THIS PERIOD FOR
MOSTLY CLEAR SKIES AND MUCH WARMER TEMPERATURES. IN OTHER WORDS...
BACK TO NORMAL SPRING-TIME WEATHER...WITH OUCH...DESERT TEMPERATURES
IN THE 90S AGAIN. ITS ALSO CONCEIVABLE THAT PHOENIX CAN REACH ITS
FIRST 100 DEG TEMP OF THE YEAR THURSDAY UNDER SOUTH WINDS/WARM
ADVECTION. ALTHOUGH GUIDANCE DISPLAYS DECREASING MODEL-TO-MODEL
CONSISTENCY...AND ENSEMBLE MEMBER SPREAD IS STILL HIGH...IT LOOKS
MORE LIKELY THAT WE WILL SEE SHOWERS AND MAYBE THUNDERSTORMS SPREAD
INTO THE AREA FRIDAY AS A DEEP UPPER LOW SETS UP JUST INLAND ALONG
THE WEST COAST. THUS POPS HAVE BEEN RAISED INTO THE SLIGHT CHANCE
CATEGORY ON FRIDAY ACROSS SOUTHEAST CALIFORNIA...AS WELL AS PORTIONS
OF SOUTHERN GILA COUNTY.

&&

.AVIATION... 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL... 

BREEZY WEST TO SOUTHWESTERLY WINDS WITH GUSTS OF 14 TO 22KTS ARE
EXPECTED THROUGH THE AFTERNOON AND EARLY EVENING ALONG WITH PARTLY
CLOUDY SKIES AND OCCASIONAL CIGS OF 8 TO 9K FT. WEST WINDS WILL
BECOME LIGHT THIS EVENING WITH MOSTLY SCATTERED SKIES. EASTERLY
COMPONENT OR LIGHT AND VARIABLE WINDS SHOULD BEGIN IN THE VERY EARLY
MORNING HOURS. 

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. 

FOR THIS AFTERNOON SKIES WILL BE CLEAR TO PARTLY CLOUDY WITH LIGHT
AND VARIABLE WINDS. DURING THE LATE AFTERNOON AND EARLY EVENING
WESTERLY COMPONENT WINDS OF 10 TO 15 KTS CAN BE EXPECTED. 

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. 

&&

.FIRE WEATHER... 
MONDAY THROUGH FRIDAY... 

A DRIER AND WARMER AIRMASS WILL STEADILY MOVE INTO THE REGION WITH
BELOW NORMAL HIGH TEMPS ON MONDAY WARMING TO ABOVE NORMAL ON TUESDAY
AND WELL ABOVE NORMAL ON WEDNESDAY WHEN HIGHS IN THE UPPER 90S...
AND ELEVATED FIRE WEATHER DANGER...IS EXPECTED. MINIMUM HUMIDITIES
IN THE MID TEENS TO LOWER 20S PERCENT RANGE ON MONDAY WILL BECOME
EVEN DRIER BY WEDNESDAY WHEN THEY WILL FALL TO THE SINGLE DIGITS.
EXPECT FAIR TO GOOD OVERNIGHT RECOVERIES ON MONDAY TO BECOME FAIR BY
TUESDAY WITH SOME IMPROVEMENT POSSIBLE ON FRIDAY. BREEZY SOUTH AND
SOUTHWESTERLY WINDS IN THE WESTERN ZONES ARE IN STORE FOR WEDNESDAY
AND IN CENTRAL AND EASTERN ZONES ON THURSDAY AND FRIDAY.

&&

.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...CB/VASQUEZ
AVIATION...SAWTELLE
FIRE WEATHER...SAWTELLE

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