Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 222230 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
330 PM MST MON DEC 22 2014

.UPDATE...
UPDATED AVIATION AND FIRE WEATHER SECTIONS.

&&

.SYNOPSIS...
HIGH PRESSURE OFF THE WEST COAST WILL RESULT IN NEAR NORMAL
TEMPERATURES WITH VARYING AMOUNTS OF HIGH CLOUDS THROUGH THE MIDDLE
OF THE WEEK. BY THURSDAY...A FAST MOVING STORM SYSTEM WILL SWING
THROUGH THE GREAT BASIN...BRINGING SLIGHTLY COOLER TEMPERATURES AND
INCREASED CLOUDINESS THAT WILL LAST THROUGH FRIDAY. DRY...AND
POTENTIALLY MUCH COOLER...WEATHER IS EXPECTED BY THE COMING WEEKEND.

&&

.DISCUSSION...
TONIGHT THROUGH WEDNESDAY...MODELS IN THE SHORT TERM ARE IN VERY
GOOD AGREEMENT THAT THE RIDGE WILL CONTINUE TO STRENGTHEN...
MAINTAINING 582-588DM 500MB HEIGHTS OVER CALIFORNIA. THE RIDGE AXIS
WILL REMAIN OFFSHORE AND CLOUD COVER WILL BE MINIMAL ACROSS THE
SOUTHWEST STATES IN THIS TIME FRAME...BUT DAYTIME TEMPS ARE EXPECTED
TO BE WARM AGAIN TUESDAY...INTO THE LOW TO MID 70S FOR THE LOWER
DESERTS ACROSS SOUTHEAST CALIFORNIA AND THE LOWER COLORADO RIVER
VALLEY. CURRENTLY...A VIGOROUS SHORT WAVE IMPULSE CONTINUES TO SLIDE
DOWN THE EASTERN PERIPHERY OF THE RIDGE...ALONG THE LEE SIDE OF THE
ROCKIES INTO THE CENTRAL CONUS. THE FAST MOVING TROUGH WILL SEND A
BACKDOOR COLD FRONT TO THE SOUTHWEST THROUGH ARIZONA OVERNIGHT...AND
THE DISTURBANCE WILL BOTTOM OUT OVER WEST TEXAS BY TUESDAY MORNING.
THE FRONT WILL BE DRY...BUT THE INTRUSION OF DRIER COLD AIR WILL
OFFSET ANY WARMING EXPECTED OVER OUR SOUTH-CENTRAL ARIZONA ZONES...
WITH JUST A FEW DEGREES OF COOLING EXPECTED ACROSS SOUTHEAST
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY. NORTH-NORTHEASTERLY
WINDS WILL INCREASE TONIGHT AND REMAIN ELEVATED THROUGH MOST OF THE
DAY TUESDAY INTO WEDNESDAY...WITH LOCAL WIND GUSTS OF 35-40 MPH
COMMON ACROSS SOUTHEAST CALIFORNIA...ALONG THE LOWER COLORADO RIVER
VALLEY...AND LOCALLY OVER HIGHER ELEVATION AND MOUNTAIN SITES IN
SOUTH-CENTRAL ARIZONA. OTHER LOCATIONS IN THE FORECAST AREA MIGHT
NOT EXPERIENCE THESE STRONG WINDS...BUT IT WILL STILL BE NOTICEABLY
BREEZY COMPARED TO THE CALM WINDS EXPERIENCED IN MANY AREAS OVER THE
LAST WEEK OR SO. THE WINDS WILL ABATE BY WEDNESDAY MORNING...AND
COOLER TEMPERATURES BACK INTO THE 60S WILL PREVAIL ACROSS THE LOWER
DESERTS.


THURSDAY -- CHRISTMAS DAY -- THROUGH THE COMING WEEKEND...FAIR MODEL
AGREEMENT IS HOLDING FOR THE LATE WEEK AND WEEKEND FORECAST AS THE
UPPER LEVEL PATTERN RETURNS TO MORE ACTIVE AND PROGRESSIVE SET-UP.
00Z SOLUTIONS FROM THE OPERATIONAL GFS AND ECMWF PLOT THE PASSING
GREAT BASIN SHORTWAVE A BIT DEEPER AND FURTHER TO THE SOUTH ACROSS
AZ LATE THURSDAY INTO FRIDAY. BOTH THESE SOLNS EVEN PAINT SOME
THICKER CLOUDS AND VERY LIGHT QPF OVER THE EASTERN AZ HIGHER
TERRAIN...AS A NARROW BAND OF ELEVATED PWATS IS DRAWN INTO THE
REGION FROM OFF THE SO CAL COAST AND BAJA CA. FCST PWAT VALUES ATTM
AREN`T OVERLY IMPRESSIVE...MOSTLY SHY OF 0.70 INCH. UPPER SHORTWAVE
WILL QUICKLY EXIT TO THE EAST FRIDAY...AS UNSETTLED BROAD
NORTHWESTERLY FLOW REMAINS OVER MUCH OF THE WEST. CONTINUED COOL
TEMPERATURES AND PERIODS OF PASSING CLOUDS ARE POSSIBLE AS SEVERAL
SHORTWAVES TRAVERSE THE FLOW.

TOWARDS THE FAR EXTENDED PERIOD OF THE LATE WEEKEND AND EARLY NEXT
WEEK...MODELS ARE HINTING AT A DRY BUT POTENTLY COLDER SYSTEM
EXPANDING SOUTHWARD FROM CANADA LATE SUNDAY. MUCH OF THE INTERIOR
WEST COULD BE IN FOR A SPELL OF BELOW NORMAL TEMPERATURES...
RESULTING IN SOME OF OUR COOLEST NIGHTS OBSERVED SO FAR THIS LATE IN
THE CALENDAR YEAR.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...SOUTHEAST
CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND KBLH...
THE APPROACH AND PASSAGE OF A DRY COLD FRONT FROM THE NORTH TONIGHT
WILL LEAD TO STRENGTHENING NORTH AND NORTHEAST WINDS...ESPECIALLY
OVER AND NEAR THE LOWER COLORADO RIVER VALLEY. WINDS IN THE LOWER
LEVELS ABOVE THE SURFACE WILL BECOME QUITE STRONG OVER SOUTHEAST
CALIFORNIA AND SOUTHWEST ARIZONA WHICH MAY LEAD TO LOW LEVEL WIND
SHEAR CONDITIONS BY 03Z IF THE SURFACE WINDS REMAIN LIGHT.
ANTICIPATE GUSTY NORTH AND NORTHEAST SURFACE WINDS ACROSS THE
FORECAST AREA BY 16Z. SKIES WILL BE CLEAR EXCEPT FOR DECREASED SLANT
VISIBILITIES THIS AFTERNOON DUE TO SMOG. SOME LOCAL BLOWING DUST IS
POSSIBLE AFTER 16Z IN THE MORE DUST PRONE AREAS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
LIGHT WINDS CAN BE EXPECTED WEDNESDAY BEFORE ANOTHER WEATHER SYSTEM
MOVES THROUGH THURSDAY AND FRIDAY FOR BREEZY CONDITIONS AT TIMES
ALONG WITH COOLER TEMPERATURES. THE SYSTEM WILL HAVE LIMITED
MOISTURE AND THERE IS ONLY A SLIGHT CHANCE OF PRECIPITATION WHICH
WILL BE LIMITED TO THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA
THURSDAY NIGHT. NO CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED.
THERE MAY BE SOME LINGERING BREEZES SATURDAY MORNING BUT OTHERWISE
WINDS THIS WEEKEND WILL BE LIGHT AND CONDITIONS WILL BE DRY.
OTHERWISE TEMPERATURES FOR THE LATTER HALF OF THIS WEEK AND WEEKEND
WILL BE NEAR TO SLIGHTLY BELOW NORMAL.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MEYERS/NOLTE
AVIATION....AJ
FIRE WEATHER...AJ






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