Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 252125
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
225 PM MST THU DEC 25 2014

.UPDATE...UPDATED AVIATION DISCUSSION.

&&

.SYNOPSIS...
A COLD FRONT WILL CONTINUE MOVING THROUGH THE AREA THIS
EVENING...RESULTING IN SCATTERED SHOWERS EAST OF PHOENIX ALONG WITH
MUCH COOLER TEMPERATURES ACROSS THE ENTIRE REGION. DRY WEATHER WITH
BELOW NORMAL TEMPERATURES ARE EXPECTED FRIDAY THROUGH EARLY NEXT
WEEK...WITH ANOTHER LOW PRESSURE SYSTEM EXPECTED TO MOVE THROUGH THE
AREA TUESDAY THROUGH THURSDAY.

&&

.DISCUSSION...
COLD FRONT CONTINUES TO RAPIDLY MOVE THROUGH THE AREA THIS AFTERNOON
AND IS POSITIONED ROUGHLY FROM WINSLOW TO YUMA AS OF 2040Z. SHOWERS
HAVE INCREASED ACROSS THE REGION SINCE ABOUT NOON AS THE FRONT HAS
MOVED INTO SOMEWHAT DEEPER MOISTURE ACROSS THE LOWER DESERTS. ACROSS
THE PHOENIX AREA RAIN SHOWERS HAVE BEEN MOSTLY IN THE FORM OF VIRGA
BUT MORE INTENSE ECHOES ARE STARTING TO FILL IN ACROSS PORTIONS OF
GILA COUNTY AND FAR NE MARICOPA COUNTY. THE CLOUD COVER HAS MANAGED
TO PUT THE BRAKES ON OUR WARMING FOR THE DAY WITH MOST SPOTS STUCK
IN THE LOW/MID 60S.

FORECAST REMAINS LARGELY ON TRACK AS THE FRONT WILL CONTINUE ITS
RAPID PUSH THROUGH ARIZONA THIS AFTERNOON AND EVENING. MOISTURE IS
MAINLY CONFINED TO THE 700-500MB LAYER WITH A FAIRLY DRY AIRMASS IN
PLACE IN THE LOWER LEVELS. WITH SURFACE DEWPOINTS IN THE MID 20S
IT`S HARD TO ENVISION MUCH PRECIP MAKING ITS WAY TO THE GROUND
ACROSS THE DESERTS. WILL CONTINUE TO MENTION 10-20 POPS FOR PARTS OF
THE EAST VALLEY AND NW PINAL COUNTY BUT THE REMAINING DESERT
LOCATIONS ARE LIKELY DONE WITH PRECIP CHANCES TODAY. MEANWHILE TO
THE NORTH/EAST OF PHOENIX...IT IS STILL LOOKING TO BE A RACE BETWEEN
FALLING SNOW LEVELS AND THE BACK EDGE OF THE PRECIPITATION. SNOW
LEVELS SHOULD FALL TO AROUND 5000FT THIS EVENING BUT THIS IS RIGHT
AROUND WHEN THE PRECIPITATION WILL BE COMING TO AN END. WILL
CONTINUE WITH THE IDEA OF A DUSTING OF SNOW IN THE HIGHEST LOCALES
EAST OF PHOENIX BUT NOTHING OF SIGNIFICANT IMPACT. AS FOR
WINDS...THE GUSTINESS WILL TAPER OFF QUICKLY BEHIND THE FRONT THIS
EVENING. THE COMBO OF RELATIVELY LIGHT WINDS AND CLEARING SKIES
SHOULD ALLOW TEMPERATURES TO DROP QUITE A BIT OVERNIGHT. CANNOT RULE
OUT SOME POCKETS OF FREEZING TEMPERATURES IN THE PROTECTED AREAS OF
LA PAZ COUNTY AS WELL AS PORTIONS OF JOSHUA TREE NATIONAL PARK
/ALTHOUGH THEIR WINDS COULD STAY ELEVATED OVERNIGHT/. WILL ISSUE A
SPECIAL WEATHER STATEMENT FOR THESE AREAS. I DON`T THINK THE AREAL
COVERAGE AND TEMPORAL EXTENT OF THE FREEZING TEMPERATURES IS ENOUGH
TO WARRANT A WARNING AT THIS POINT.

LOOKING AHEAD TO FRIDAY HOWEVER...COOL NORTHWESTERLY FLOW ALOFT WILL
CONTINUE TO USHER WELL BELOW NORMAL TEMPERATURES INTO THE REGION.
DAYTIME HIGHS FROM BIAS CORRECTED AND RAW GUIDANCE SUGGEST HIGHS
WON`T BREAK OUT OF THE MID 50S. CONSEQUENTLY LOW TEMPERATURES WILL
FALL WELL BELOW NORMAL AND NUMEROUS LOCATIONS ACROSS THE DESERTS
COULD SEE FREEZING TEMPERATURES. WILL STICK WITH THE IDEA OF THE
COLDEST TEMPS IN LA PAZ...NW MARICOPA...AND NW PINAL COUNTIES
ALTHOUGH THE NORMALLY COLDER SOUTHEAST VALLEY LOCATIONS COULD ALSO
SEE FREEZING TEMPS EARLY SATURDAY MORNING. FREEZE WARNING WILL
REMAIN INTACT AS ISSUED EARLIER TODAY...ONLY QUESTION AT THIS POINT
IS IF THE PHOENIX METRO SHOULD BE INCLUDED WITHIN THE WARNING BASED
ON THE SOUTHEAST VALLEY`S FREEZE POTENTIAL.

SATURDAY AND SUNDAY WILL SEE CONTINUED NORTHWESTERLY FLOW BUT
HEIGHTS AND BL TEMPS WILL RISE SLIGHTLY EACH DAY. WHILE HIGHS WILL
STILL TOP OUT IN THE MID/UPPER 50S EACH DAY...CLOUDS WILL BE ON THE
INCREASE AHEAD OF A FAST MOVING SHORTWAVE WHICH SHOULD HELP MITIGATE
THE CHANCE OF ANOTHER ROUND OF EARLY MORNING FREEZING TEMPERATURES.

TAKING A BROAD BRUSH APPROACH FROM THE WIDELY VARYING MODEL FCST FOR
THE EXTENDED...MOSTLY DRY AND COOL NORTHWEST FLOW WITH EMBEDDED
SHORTWAVES WILL HOLD OVER THE REGION FOR EARLY NEXT WEEK...KEEPING
TEMPERATURES AT OR BELOW SEASONAL NORMALS WHILE PERIODICALLY BRINGING
CLOUDS INTO THE REGION. 00Z OPERATIONAL SOLNS FROM THE GFS/ECMWF/GEM
ALL ADVERTISE A LARGE UPPER LOW DEVELOPING INTO THE SW STATES WITH
CONSIDERABLE MOISTURE FIELDS AND QPF VALUES BY TUESDAY.
MEANWHILE...ONLY A SMALL PERCENTAGE OF ENSEMBLE MEMBERS SUPPORT
THEIR OPERATIONAL COUNTERPARTS. FOR NOW...MAINTAINED A COOL FORECAST
FOR BOTH HIGHS AND LOWS AND BLENDED INTO CLIMO POP INFLUENCE IN THE
EXTENDED FOR TUESDAY AND BEYOND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A COLD FRONT CONTINUES TO PUSH EASTWARD THROUGH CENTRAL AZ THIS
AFTERNOON. WESTERLY WINDS HAVE INCREASED TO 10 TO 20 KT IN THE
PHOENIX AREA ALONG AND BEHIND THE FRONT. MEANWHILE...CLOUDS HAVE
THICKENED WITH CIGS GENERALLY IN A 8-10K FT RANGE.
HOWEVER...OCCASIONAL CIGS AS LOW AS 7K FT ARE POSSIBLE THROUGH 23Z
ALONG WITH AREAS OF VIRGA. THEREAFTER...CEILINGS WILL LIFT AND A
RAPID CLEARING TREND WILL TAKE PLACE AS DRIER AIR WORKS ITS WAY INTO
THE AREA. WINDS WILL SUBSIDE AFTER SUNSET...BUT WILL PERSIST OUT OF
THE WEST THROUGH AT LEAST 09Z. A SWITCH TO DOWNSLOPE EASTERLY FLOW
IS ANTICIPATED IN SOME SPOTS...PARTICULARLY AT KIWA BUT LESS LIKELY
AT KPHX.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND
KBLH...
BREEZY CONDITIONS WILL PERSIST OVERNIGHT IN THE WAKE OF A COLD FRONT
THAT MOVED THROUGH THE AREA EARLY THURSDAY. SOMEWHAT LIGHTER WINDS
ARE EXPECTED FRIDAY.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
TRANQUIL DRY AND ABNORMALLY COOL WEATHER WILL PREVAIL OVER THE
WEEKEND INTO EARLY NEXT WEEK WITH NO FIRE WEATHER CONCERNS. ONLY A
BRIEF PERIOD OF SOMEWHAT GUSTY WINDS DOWN THE COLORADO RIVER VALLEY
WILL DISRUPT OTHERWISE NEARLY CALM CONDITIONS. AFTERNOON HUMIDITY
VALUES WILL ONLY FALL INTO A 20 TO 30 PERCENT RANGE WITH GOOD TO
EXCELLENT OVERNIGHT RECOVERY. THE POTENTIAL EXISTS FOR ANOTHER WIND
PRODUCING AND WETTER WEATHER SYSTEM AFFECTING THE DISTRICT BY THE
MIDDLE OF NEXT WEEK.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FREEZE WARNING FROM MIDNIGHT FRIDAY NIGHT TO 8 AM MST SATURDAY
     AZZ021-022-028.

CA...NONE.

&&

$$

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

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







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