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000
FXUS65 KPSR 221720
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1020 AM MST SUN NOV 22 2009

.SYNOPSIS...
MOSTLY CLEAR NIGHTS AND SUNNY DAYS ARE EXPECTED TO CONTINUE AT LEAST
THROUGH THANKSGIVING. HIGH PRESSURE ALOFT BETWEEN HAWAII AND BAJA
CALIFORNIA IS EXPECTED TO BUILD NORTHEAST OVER OUR AREA WITH WARMER
WEATHER WEDNESDAY AND THANKSGIVING DAY. TEMPERATURES WILL RISE TO
WELL ABOVE AVERAGE FOR LATE NOVEMBER BY THANKSGIVING DAY...IN THE
UPPER 70S TO NEAR 80 DEGREES IN THE DESERT AREAS INCLUDING PHOENIX...
YUMA AND EL CENTRO.

&&

.DISCUSSION...
UNDER SUNNY SKIES WITH SOME HIGH THIN CIRRUS CLOUDS...TEMPERATURES
WERE GENERALLY CLOSE TO THE SAME OR A COUPLE OF DEGREES COOLER LATE
THIS MORNING COMPARED WITH THE SAME TIME YESTERDAY. WINDS WERE
GENERALLY CALM OR LIGHT...MOSTLY FROM FROM THE NORTH AND EAST IN
SOUTH-CENTRAL AND SOUTHWEST ARIZONA INCLUDING THE GREATER PHOENIX
AND YUMA AREAS.

FORECAST LOOKS AS IF IT IS ON THE RIGHT TRACK...NO UPDATES.

PREVIOUS DISCUSSION...
AS OF 1 AM THIS MORNING SKIES WERE CLEAR ACROSS THE CWA...AND THE
AIRMASS WAS QUITE DRY WITH PWAT BELOW ONE QUARTER INCH. SURFACE
DEWPOINTS OVER THE DESERTS WERE LOW...RANGING FROM THE UPPER TEENS
TO AROUND 30. FOR TODAY INTO MONDAY...PROGS AGREE THAT THE STORM
TRACK WILL REMAIN WELL TO OUR NORTH...WITH A DRY NWLY FLOW IN PLACE
ACROSS THE CWA. A SERIES OF DISTURBANCES WILL PASS BY TO OUR
NORTH...KEEPING TEMPERATURES NEARLY FLAT LINED...AND SLIGHTLY ABOVE
SEASONAL NORMALS. A FEW HIGH CLOUDS WILL MOVE THROUGH THE FLOW...BUT
THEY WILL BE ON THE THIN SIDE...FOR MOSTLY SUNNY DAYS AND CLEAR
NIGHTS.

TUESDAY INTO THE MIDDLE PORTION OF THE WEEK...BOTH THE GFS AND ECMWF
AGREE THAT HIGH PRESSURE WILL BUILD OVER THE WESTERN STATES...BUT
THERE WILL BE A SPLIT IN THE FLOW WITH A WEAK SRN BRANCH AND A BAGGY
TROF OR POSSIBLY CLOSED UPPER LOW SITUATED TO OUR SOUTH. LATEST GFS
IS A BIT MORE AGGRESSIVE IN DEVELOPING THIS LOW OVER BAJA...AND
ATTEMPTS TO WRAP MID AND HIGH CLOUDS INTO OUR CWA FROM THE SOUTHEAST
WED NIGHT THROUGH THURSDAY NIGHT. FEEL THIS IS OVERDONE...AND ANY
HIGH CLOUDINESS THAT ENTERS OUR CWA WILL BE ABOVE 500MB AND ON THE
THIN SIDE. THUS SKIES WILL STILL BE MOSTLY SUNNY. OF COURSE...THE
PROXIMITY OF THE LOW TO OUR SOUTH WILL KEEP HEIGHTS/THICKNESSES FROM
RISING TOO MUCH AND AS SUCH THE WARMING TREND DURING THIS PERIOD
WILL BE MINIMAL. STILL...EXPECT HIGHS ABOVE CLIMO AND IN THE MID TO
UPPER 70S EACH DAY OVER OUR WARMER DESERTS.

LATE IN THE FORECAST PERIOD...FRIDAY INTO SATURDAY...MED RANGE PROGS
START TO DIVERGE...AS IS OFTEN THE CASE. BOTH GFS AND ECMWF
ADVERTISE A RATHER PROGRESSIVE SHORT WAVE TO MOVE INTO THE WESTERN
STATES...AND ACROSS ARIZONA. HOWEVER...GFS IS MORE PROGRESSIVE AND
KEEPS THE SYSTEM WELL TO OUR NORTH WITH A DRY WLY FLOW IN PLACE BOTH
DAYS. EUROPEAN DIGS THE SYSTEM MORE TO THE SOUTHEAST...AND BRINGS A
MUCH COOLER AIRMASS INTO ARIZONA BY SATURDAY. HPC EXTENDED PERIOD
GUIDANCE SUGGESTS A MODEL BLEND SOLUTION FOR SATURDAY...AND THE
TRACK RECORD OF THE EUROPEAN OVER THE GFS WOULD SUGGEST THAT IT
MIGHT END UP BEING THE SUPERIOR MODEL. AS SUCH HAVE LOWERED TEMPS A
FEW DEGREES ON SATURDAY TO REFLECT THE COOLER ECMWF SOLUTION...AND
ADDED SOME CLIMO SINGLE DIGIT POPS INTO THE FORECAST AS WELL.

&&

.AVIATION...
SOUTHEAST CA...SOUTHWEST AND SOUTH CENTRAL AZ...INCLUDING KIPL...
KBLH...KPHX...AND KIWA.

A WEATHER SYSTEM PASSING WELL TO THE NORTH TODAY AND TONIGHT WILL
HAVE NO APPRECIABLE EFFECT ON SURFACE WINDS. THUS LIGHT WINDS WILL
CONTINUE TODAY...EVEN A BIT LIGHTER THAN YESTERDAY. SOMEWHAT
STRONGER WINDS CAN BE EXPECTED MONDAY AFTERNOON...PERHAPS GETTING
ABOVE 10 KTS FROM THE NORTH DOWN THE LOWER COLORADO RIVER VALLEY
INCLUDING KBLH. SKIES WILL BE CLEAR EXCEPT FOR MINOR AMOUNTS OF HIGH
CIRRUS CLOUDS ABOVE 20 THOUSAND FEET ASL.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
HIGH PRESSURE WILL BE IN PLACE OVER THE SOUTHWEST TUESDAY THROUGH
FRIDAY FOR SLIGHTLY WARMER TEMPERATURES...LOW DAYTIME HUMIDITY AND
MODEST OVERNIGHT RECOVERY. WINDS WILL FAVOR NORTH AND NORTHEAST
DIRECTIONS THROUGH THANKSGIVING DAY...LOCALLY WINDY AT TIMES AT THE
RIDGETOPS...WITH LIGHT WINDS FRIDAY. THERE ARE CONFLICTING SIGNALS
AS TO WHAT THE WEATHER WILL DO AFTER FRIDAY. A COOLING TREND IS
ANTICIPATED ALONG WITH STRONGER WINDS. GIVEN THE
UNCERTAINTY...FORECASTS REFLECT CONSERVATIVE TRENDS.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...ELLIS/CB
AVIATION...ELLIS/AJ
FIRE WEATHER...AJ


Additional Links:

Forecast Discussion – Flagstaff NWS Office

Forecast Discussion – Phoenix NWS Office

Forecast Discussion – Tucson NWS Office

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