Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 190414
AFDPSR

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

.SYNOPSIS...
HIGH PRESSURE BUILDING INTO THE DESERT SOUTHWEST FROM THE WEST WILL
RETURN 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 DEVELOP DOWN INTO THE WESTERN STATES.

&&

.DISCUSSION...
SHORTWAVE AXIS AND ASSOCIATED CLOUD/SHOWER ACTIVITY QUICKLY CLEARED
TO OUR EAST EARLIER THIS AFTERNOON...ALLOWING FOR A FEW HOURS OF
INSTABILITY CU TO TRY AND POP OVER THE WARMING DESERT FLOORS. THE
TRANSITION TO NORTHWESTERLY FLOW WAS EVIDENT ON AFTERNOON RADAR
LOOPS...WITH ANY LINGERING LIGHT SHOWER ACTIVITY SKIRTING THE HIGH
TERRAIN TO OUR EAST. ALL ACTIVITY...BOTH CU AND RADAR
RETURNS...QUICKLY DIMINISHED AFTER SUNSET. ONLY SOME LIMITED AMOUNTS
OF LOW TO MID LEVEL STRATUS ALONG THE PENINSULA RANGES OF BAJA AND
FAR SOUTHERN CA AND OVER THE SOUTHERN GILA COUNTY HIGHER TERRAIN
REMAIN.

MINOR UPDATES WERE NEEDED TO ADJUST OVERNIGHT SKY FORECASTS TO
CURRENT TRENDS. VERY LITTLE CHANGE NOTED ON AREA DEWPOINTS WHEN
COMPARED TO 24 HOURS AGO...WITH MID TO UPPER 40 DEGREE READINGS
STILL HOLDING OVER THE LOWER DESERT LOCALES. EXPECT A MUCH COOLER
NIGHT WITHOUT THE INSULATING CLOUD COVER...WHICH COULD RESULT IN
SOME AREAS SEEING ANOTHER ROUND OF AM FOG...PARTICULARLY DOWN ALONG
THE LOWER GILA RIVER DRAINAGE TOWARDS YUMA AND OVER THE DUNES IN
IMPERIAL COUNTY. NAM FCST SOUNDINGS LOOK SIMILAR TO THOSE FROM 24
HOURS AGO WITH LOW LEVEL INVERSIONS AND A SMALL TEMP-DEWPOINT SPREAD
HOLDING THROUGH MID MORNING BEFORE EVENTUALLY BREAKING DOWN. REST OF
THE SHORT TERM FORECAST ON TRACK...FURTHER DETAILS AVAILABLE IN
PREVIOUS DISCUSSION BELOW.

&&

.PREVIOUS DISCUSSION /ISSUED AT 125 PM MST/1225 PST/...
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...
MOSTLY CLEAR SKIES EXPECTED THROUGH THE OVERNIGHT AND ARE ALREADY
NOTED ON AREA OBS. THERE COULD BE SOME PATCHES OF LOW LEVEL
CLOUDS...ESPECIALLY ALONG NEARBY TERRAIN SLOPES...THAT EVENING IR
COULD BE MISSING. AREA DEWPOINTS REMAIN AND COOL TEMPERATURES
TONIGHT COULD PROMOTE SOME MIST/FOG DEVELOPMENT BUT CONFIDENCE NOT
HIGH ENOUGH ATTM TO INCLUDE MENTION IN THE TAF. OVERNIGHT WINDS TO
FOLLOW TYPICAL SESTRLY HEADINGS...GNLY 8KTS OR LESS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND
KBLH...
MOSTLY CLEAR SKIES TO HOLD OVERNIGHT WITH SOME PATCHES OF LOW TO MID
LEVEL CLOUDS ALONG THE TERRAIN TO THE WEST OF KIPL. AREA DEWPOINTS
REMAIN HIGH AND THOSE COMBINED WITH COOL TEMPERATURES TONIGHT COULD
PROMOTE ANOTHER ROUND OF MIST/FOG DEVELOPMENT THROUGH THE EARLY TO
MID MORNING. CONFIDENCE NOT HIGH ENOUGH TO WARRANT MENTION IN THE
TAFS ATTM. OVERNIGHT WINDS TO FOLLOW TYPICAL DIURNAL
HEADINGS...WESTERLY FOR KIPL AND NORTHERLY FOR KBLH...WITH MOSTLY
LIGHT SPEEDS.

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...NOLTE
PREVIOUS DISCUSSION...PERCHA
AVIATION...NOLTE
FIRE WEATHER...KUHLMAN









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