Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 182039
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
140 PM MST THU DEC 18 2014

...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...
AFTER SEVERAL DAYS OF COOL...AND MOIST CONDITIONS...HIGH PRESSURE
BUILDING INTO THE DESERT SOUTHWEST FROM THE WEST IS EXPECTED TO
BRING DRY CONDITIONS...AND A GRADUAL WARMING TREND BACK TO THE
REGION THROUGH MUCH OF NEXT WEEK. COOLER TEMPERATURES ARE THEN
POSSIBLE BY THE END OF NEXT WEEK AS A RATHER STRONG...AND COLD
WEATHER SYSTEM BEGINS TO DROP SOUTHWARD INTO THE WESTERN US.

&&

.DISCUSSION...
THE EXPECTED CHANGE TO A DRY...AND WARMER WEATHER REGIME CAN ALREADY
BE SEEN THIS AFTERNOON AS THE LAST IN A SERIES OF SHORTWAVES BEGINS
TO MOVE OFF TO THE EAST...INTO EASTERN AZ AND NM. BEHIND THIS
SYSTEM...LATEST SATELLITE IMAGERY AND SFC OBSERVATIONS ARE NOW
SHOWING A DISTINCT CLEARING TREND ACROSS SE CA AND SW AZ...AND INTO
SOUTH-CENTRAL AZ...WHICH IS ALLOWING TEMPERATURES AT MANY LOWER
DESERT LOCATIONS ACROSS SE CA AND SW AZ TO RECOVER INTO THE 60S THIS
AFTERNOON. THIS CLEARING/DRYING TREND IS FORECAST TO CONTINUE INTO
THE EVENING...WITH THE LAST FEW LIGHT SHOWERS ENDING OVER THE HIGHER
TERRAIN OF SOUTHERN GILA COUNTY SHORTLY AFTER SUNSET.

HIGH PRESSURE BUILDING INTO FROM THE WEST IS FORECAST TO KEEP DRY
CONDITIONS IN PLACE...AND ALLOW DAYTIME TEMPERATURES TO RISE A BIT
ON FRIDAY AND SATURDAY. SOME MID AND HIGH CLOUDINESS WILL LIKELY
RETURN TO THE REGION ON FRIDAY NIGHT AND SATURDAY AS ANOTHER
WEAK...BUT DRY SHORTWAVE PASSES OVER THE REGION. AFTER HIGHS IN THE
MID TO UPPER 60S ON SATURDAY...70S ARE EXPECTED TO RETURN TO SE
CA...AND TO THE REST OF OUR LOWER DESERT LOCATIONS ON MONDAY AS
STRONG HIGH PRESSURE RIDGING BECOMES ESTABLISHED ALONG THE WEST
COAST. RELATIVELY HIGH 500MB HEIGHTS (AOA 570DM) AND A DRY
NORTHWESTERLY FLOW WILL THEN ALLOW LOWER DESERT HIGHS TO RISE INTO
THE LOW TO MID 70S FROM TUESDAY INTO THURSDAY UNDER MOSTLY CLEAR
SKIES. AS FAR AS THE FORECAST FOR END OF NEXT WEEK IS
CONCERNED...ALTHOUGH THE LATEST EURO...GEM...AND OPERATIONAL GFS
HAVE NOW BACKED OFF SOMEWHAT ON THE AMPLITUDE OF A STRONG...AND COLD
LONG-WAVE TROF THAT IS FORECAST TO DIG SOUTHWARD INTO THE WESTERN
US...A COOLING TREND IS STILL EXPECTED TO BEGIN BY NEXT
FRIDAY...WHICH WOULD BRING OUR TEMPERATURES DOWN CLOSER TO SEASONAL
NORMALS...ALTHOUGH THE LATEST 13KM PARALLEL GFS CONTINUES TO HOLD ON
TO A MUCH COLDER SOLN.

&&

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

BREAKS IN CEILINGS ARE STARTING TO SHOW EARLY THIS AFTERNOON AS THE
DEPARTING TROUGH CONTINUES EASTWARD...SCT TO BKN DECKS AT KSDL AND
KPHX 4500FT WILL IMPROVE EVEN MORE BY 00Z FRIDAY. WINDS REMAIN LIGHT
AND MOSTLY DIURNAL...AROUND 7-8 KTS EXPECTED THROUGH THE EVENING
HOURS. RAIN CHANCES WILL DIMINISH THIS AFTERNOON AND SHOULD REMAIN
CLEAR THROUGH THE NEXT 24 TO 48 HOURS. ANOTHER ROUND OF MID AND HIGH
CLOUDS WILL RETURN FRIDAY AFTERNOON WITH ANOTHER SHORTWAVE PUSHING
THROUGH.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND
KBLH...
MOSTLY CLEAR SKIES ARE NOW IN PLACE AND WILL DOMINATE THROUGH 18Z
FRIDAY BEFORE MID AND HIGH CLOUDS BUILD BACK IN. RAIN CHANCES
DIMINISH TODAY AND SHOULD REMAIN DRY THROUGH THE NEXT 24 TO 48
HOURS. MOSTLY DIURNAL WIND PATTERNS WILL BE IN PLACE WITH A FAVOR
FROM THE NORTHERLY DIRECTION AS A SHORTWAVE TROUGH MOVES THROUGH
FRIDAY.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
UPPER LEVEL RIDGING WILL TAKE OVER STARTING LATE SATURDAY WITH
WARMING TEMPERATURES AND SLIGHTLY DRIER CONDITIONS. HIGHS WILL WARM
TO ABOVE NORMAL STARTING SUNDAY WITH LOWER DESERT HIGHS IN THE LOW
TO MID 70S FOR LATE IN THE PERIOD. HUMIDITIES WILL REMAIN FAIRLY
HIGH THROUGH THE PERIOD WITH MINIMUM VALUES STAYING ABOVE 25
PERCENT. WINDS WILL REMAIN LIGHT FOR THE MOST PART WITH THE
EXCEPTION OF OCCASIONAL AFTERNOON BREEZINESS MAINLY CONFINED TO
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA SUNDAY THROUGH TUESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...PERCHA
AVIATION...DEWEY
FIRE WEATHER...KUHLMAN







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