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000
FXUS65 KPSR 131524
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
825 AM MST FRI DEC 13 2013

.SYNOPSIS...
SUNNY SKIES AND COOLER TEMPERATURES WILL MOVE INTO THE AREA TODAY IN
THE WAKE OF A DEPARTING UPPER LEVEL LOW PRESSURE SYSTEM. HIGH
PRESSURE WILL THEN BUILD INTO THE AREA FROM THE WEST THIS WEEKEND
FOR A WARMING TREND UNDER GENERALLY CLEAR SKIES. DESPITE SOME HIGH
CLOUD COVER...HIGH PRESSURE WILL CONTINUE TO BUILD THROUGH THE
MIDDLE OF NEXT WEEK ALLOWING HIGH TEMPERATURES TO CLIMB WELL ABOVE
SEASONAL NORMALS AND INTO THE MID TO UPPER 70S OVER THE WARMER
DESERTS.

&&

.DISCUSSION...
AFTER A BOUT OF ISOLATED SHOWERS AND THUNDERSTORMS MOST OF THE NIGHT
OVER GENERALLY THE NORTHEAST QUARTER OF AZ...ASSOCIATED WITH A
DEPARTING SHORTWAVE...A SECOND SHORTWAVE FROM THE NORTHWEST WAS
APPROACHING THE STATE. ALTHOUGH PLOT CHARTS SHOW LINGERING MOISTURE
AT AND BELOW 700 MB OVER THE EASTERN HALF OF AZ...MOST DYNAMICS AND
UPPER SUPPORT FOR SHOWERS TODAY...IF ANY...SHOULD BE LIMITED TO
SECTIONS OF NORTHEAST AND EAST CENTRAL AZ OUTSIDE OUR FORECAST AREA.
THEREFORE THE DRIER AND COOLER FORECAST GOING FOR TODAY LOOKS OK. NO
UPDATES PLANNED. OTHERWISE...DRY AND WARMER WEATHER IS STILL
FORECAST THIS WEEKEND. PREVIOUS DISCUSSION BELOW STILL APPLIES.

PREVIOUS DISCUSSION...2 AM MST...
EARLY THIS MORNING...A RATHER DRY UPPER LEVEL LOW CONTINUED TO SCOOT
QUICKLY EASTWARD ACROSS ARIZONA AND BY 12Z IT WILL OPEN UP WITH THE
TROF AXIS NEARING THE AZ/NM BORDER. THIS LOW...MORE EASILY SEEN IN
VAPOR IMAGERY...BROUGHT LITTLE IF ANY PRECIP TO OUR AREA YESTERDAY
AND AT 2 AM SKIES WERE BASICALLY CLEAR ACROSS SERN CA AS WELL AS THE
SRN AZ DESERTS. SURFACE DEWPOINTS WERE ON THE LOW SIDE OVER THE
DESERTS AND MOSTLY WERE IN THE 20S TO LOW 30S EARLY THIS MORNING.
MEANWHILE...AN UPPER RIDGE WAS BUILDING IN THE EASTERN PACIFIC WITH
THE AXIS JUST OFF THE WEST COAST...AND ANOTHER QUICK MOVING SHORT
WAVE WAS DIVING DOWN THE FRONT SIDE OF THE RIDGE AND INTO THE GREAT
BASIN. THIS FEATURE WILL FOLLOW QUICKLY ON THE HEELS OF THE
DEPARTING LOW...AND WILL DROP THRU THE FOUR CORNERS THIS AFTERNOON
AND EVENING...BRINGING A FEW CLOUDS TO SOUTH CENTRAL AZ BUT NO
PRECIP. COMBINED WITH THE LOW NOW MOVING EAST ACROSS THE STATE IT
WILL USHER IN COOLER AIR...AND HIGH TEMPS TODAY WILL FALL AT LEAST
SEVERAL DEGREES AND DOWN INTO THE MID 60S OVER THE CENTRAL AZ
DESERTS. PHOENIX SHOULD SEE A HIGH AROUND 65 DEGREES TODAY WHICH IS
ROUGHLY AT SEASONAL NORMALS.

GUIDANCE IS CONSISTENT IN CALLING FOR THE UPPER RIDGE TO GRADUALLY
MOVE INLAND AND INTO THE DESERT SOUTHWEST THIS WEEKEND...BRINGING
DRY CONDITIONS...SUNNY DAYS...AND WARMER TEMPERATURES...TO THE
REGION. BY SUNDAY EXPECT HIGHS IN THE UPPER 60S TO LOW 70S OVER MOST
OF THE WARMER LOWER DESERTS. THE RIDGE WILL SETTLE IN OVER THE
DESERT SOUTHWEST THROUGH THE MIDDLE OF NEXT WEEK...AND DESPITE THE
PRESENCE OF SOME HIGH CLOUDINESS...HIGH TEMPS WILL CLIMB ANOTHER
SEVERAL DEGREES OR MORE AS THE WARM AIR ALOFT MIXES TO THE SURFACE.
DESERT HIGHS WILL RISE INTO THE MID OR EVEN UPPER 70S MONDAY THROUGH
WEDNESDAY.

GFS AND ECMWF...AS WELL AS GFS ENSEMBLES...ALL CALL FOR A VERY DEEP
UPPER TROF TO RAPIDLY DEVELOP ACROSS THE WESTERN AND CENTRAL CONUS
STARTING NEXT THURSDAY AND CONTINUING INTO THE WEEKEND. IT WILL
LIKELY STAY RELATIVELY DRY THURSDAY...BUT AS COOLER AIR STARTS TO
PLUNGE SOUTH AND INTO THE AREA...HIGH TEMPS WILL START TO FALL OFF.
HIGHS WILL FALL SEVERAL DEGREES BUT REMAIN A BIT ABOVE NORMAL
THURSDAY UNDER PARTLY TO MOSTLY SUNNY SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...SOUTHEAST
CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND KBLH...

SURFACE GRADIENTS REMAIN LIGHT IN THE WAKE OF EXITING LOW PRESSURE
SUPPORTING LIGHT WINDS...GENERALLY 6KTS OR LESS...THROUGH THE
MAJORITY OF THE TAF PERIOD. WINDS WILL SUBTLY FOLLOW TYPICAL
DIURNAL HEADINGS...OTHERWISE REMAIN VARIABLE IN NATURE. NORTHERLY
HEADINGS APPROACHING 10KTS MAY BE POSSIBLE OVERNIGHT AT
KBLH...REMAINING STEADY THROUGH THE DAY SATURDAY. SOME BOUNDARY
LAYER MOISTURE LINGERS TODAY...SO EXPECT AFTERNOON FEW TO SCT CU
DEVELOPMENT ACROSS THE REGION NEAR 8 TO 10KFT WHILE DISSIPATING AND
CLEARING INTO THE EARLY EVENING HOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
HIGH PRESSURE WILL KEEP DRY AND WARM CONDITIONS FOR THE REGION
THROUGH THE LATE WEEKEND AND INTO NEXT WEEK. EXPECT TYPICAL AND
TERRAIN DRIVEN WIND PATTERNS WITH MOSTLY CLEAR SKIES. HIGH PRESSURE
WILL BEGIN TO BREAK DOWN BY THE MIDDLE OF THE WEEK AS THE PACIFIC
STORM TRACK BEGINS TO EXPAND BACK INTO THE SOUTHWEST STATES BY
THURSDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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DISCUSSION...VASQUEZ/CB
AVIATION...NOLTE
FIRE WEATHER...NOLTE