000
FXUS65 KPSR 100526 CCA
AFDPSR

AREA FORECAST DISCUSSION...............COR
NATIONAL WEATHER SERVICE PHOENIX AZ
1025 PM MST TUE FEB 9 2010

CORRECTION FROM VANDENBURG SNOW LEVEL MENTIONED IN DISCUSSION

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL BRING RAIN AND MOUNTAIN SNOW SHOWERS...
AS WELL AS A SLIGHT CHANCE OF THUNDERSTORMS...OVER FAR SOUTHEAST
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY TONIGHT INTO EARLY
WEDNESDAY...AND MAINLY OVER SOUTHWEST AND SOUTH-CENTRAL ARIZONA
WEDNESDAY AND WEDNESDAY EVENING. DRIER CONDITIONS WILL PREVAIL
THURSDAY AS THE LOW MOVES OFF TO OUR EAST...THOUGH IT WILL REMAIN
RATHER COOL. DRY AND WARMER WEATHER WILL COMMENCE FRIDAY AND
CONTINUE THROUGH EARLY NEXT WEEK AS A RIDGE OF HIGH PRESSURE BECOMES
ESTABLISHED OVER THE WESTERN UNITED STATES. TEMPERATURES WILL BE
SEVERAL DEGREES ABOVE NORMAL SATURDAY THROUGH AT LEAST NEXT TUESDAY.

&&

.DISCUSSION...
A POWERFUL DEVELOPING PACIFIC LOW PRESSURE SYSTEM THAT HAD BEEN
MOVING QUICKLY DOWN THE WEST COAST FROM OREGON MONDAY/MONDAY NIGHT
ARRIVED IN SOUTHERN CA TUESDAY AFTERNOON WITH A BANG. HEAVY RAIN...
THUNDERSTORMS AND MORE DEVELOPED FROM SANTA BARBARA TO SAN DIEGO
...AND OVER THE ADJACENT COASTAL MOUNTAINS. ITS A COLD STORM...AND
WEATHER BALLOON SOUNDINGS DETECTED THE SNOW LEVEL RANGED FROM 3000
FEET AT VANDENBURG AFB...WITH THE COLD CORE STORM CENTER...TO 5000
FEET AT SAN DIEGO. THE DRA SOUNDING NEAR LAS VEGAS DETECTED A SNOW
LEVEL AT 4800 FEET.

MODELS SO FAR ARE DOING A GREAT JOB IN THE SHORT TERM...MEANING THE
LOW PRESSURE SYSTEM CONTINUED TO MOVE SOUTH/SOUTHEAST. THE EUROPEAN
AND GFS MODELS SINK THIS SYSTEM SOUTH INTO NORTHERN BAJA CA BY 12Z
WED. THERE IS A CAVEAT THOUGH. ABUNDANT SATELLITE DERIVED 300 AND
250 MB JET STREAM WINDS...DERIVED FROM THE SUBTROPICAL CLOUD PLUME
ACROSS BAJA CA AND NORTHWEST MEXICO AT 00Z...SHOWED A SUBTROPICAL
JET SLIGHTLY IN EXCESS OF 130 KNOTS. THE CAVEAT IS...A SUBTROPICAL
JET THIS STRONG MAY SERVE TO LIMIT THE SOUTHWARD MOVEMENT OF THE LOW
PRESSURE SYSTEM...WITH THE SYSTEM TRACKING A LITTLE FARTHER NORTH
INTO SOUTHERN AZ THAN MODELS FORECAST. MORE MOISTURE AND DYNAMICS
COULD BE DIRECTED TOWARD PHOENIX AND VICINITY ON WED (OF MOST OF
SOUTH CENTRAL AZ) WITH ISOLATED THUNDERSTORMS.

BACK TO SNOWFALL. A WINTER WEATHER ADVISORY FOR JOSHUA TREE NATIONAL
PARK IN SOUTHEAST CA WILL CONTINUE TONIGHT. WE WILL OPT TO UPDATE
THE ADVISORY FOR MORE SNOW...AND TAKE THE ACCUMULATING SNOW LEVEL
DOWN TO 3500 FEET. 3 TO 5 STORM TOTAL INCHES ABOVE 3500 FEET IS NOW
EXPECTED IN JOSHUA TREE. UPDATES WILL COME OUT SHORTLY. REASONING...
APPEARS FROM THE COASTAL WEATHER BALLOON SOUNDINGS THAT THE 3000
FOOT SNOW LEVEL IS FOLLOWING THE MINUS 8 DEGREE C ISOTHERM...WHICH
MOVES INTO JOSHUA TREE AROUND 06Z OR 10 PM PST. 3000 FEET WILL BE
THE SNOW LINE...BUT ACCUMULATIONS LIKELY ABOVE 3500 FEET.

PRECIPITATION IN SOUTHEAST CA AND THE COLORADO RIVER VALLEY...SOME
HEAVY RAIN SHOWERS WITH ISOLATED THUNDERSTORMS WILL SPREAD ACROSS
THE SOUTHEAST CA DESERTS SHORTLY...THEN MOVE INTO THE COLORADO RIVER
VALLEY LATER TONIGHT. SHOWERS WILL THEN SPREAD EAST ACROSS MOST OF
SOUTHERN AZ ON WEDNESDAY AS THE UPPER LOW TRACK EAST NEAR THE
INTERNATIONAL BORDER.

UPDATES FOR THE SNOW ADVISORY WILL COME OUT SHORTLY...OTHERWISE
REMAINDER OF FORECASTS LOOK OK FOR NOW.  PREVIOUS DISCUSSION BELOW
STILL APPLIES EXCEPT FOR A CHANGE IN SNOW LEVELS AND ACCUMULATIONS
IN SOUTHEAST CA.

PREVIOUS DISCUSSION...
UPPER LOW THAT WILL AFFECT OUR WEATHER DURING THE NEXT COUPLE OF
DAYS WAS CENTERED SW OF SAN FRANCISCO AS OF 21Z (2 PM MST)...AND
CONTINUED TO MOVE TOWARD THE SSE AT ABOUT 20 KNOTS. AS MENTIONED
THIS MORNING...NUMERICAL MODELS ARE IN GOOD AGREEMENT REGARDING
TRACK OF THIS LOW...KEEPING IT ON A PATH THAT PARALLELS THE
CALIFORNIA COAST DURING THE NEXT 18 HRS...PLACING IT JUST WEST OF
SAN DIEGO BY 12Z WEDNESDAY...THEN MOVING IT SLOWLY EAST ALONG THE
INTERNATIONAL BORDER TO JUST SOUTH OF THE ARIZONA-NEW MEXICO BORDER
BY 12Z THURSDAY. AS SUCH...STRONGEST FORCING/UVV AND BEST CHANCE FOR
PRECIPITATION WILL TRACK ACROSS FAR SOUTHEAST CALIFORNIA AND
SOUTHWEST ARIZONA TONIGHT...ACROSS SOUTHERN QUARTER OF ARIZONA ON
WEDNESDAY...AND OVER SOUTHEAST ARIZONA WEDNESDAY NIGHT (PRINCIPAL
UPPER SUPPORT AND BEST CHANCE FOR PRECIPITATION DOES AN `END RUN`
AROUND SOUTH-CENTRAL ARIZONA). GIVEN ONLY MODEST MOISTURE
AVAILABILITY AS WELL AS THE FACT THE STORM WILL TRACK WELL SOUTH OF
OUR FORECAST AREA...PRECIP TOTALS FROM THIS STORM WILL BE RATHER
MODEST...LESS THAN ONE HALF INCH AT MOST LOCALES. TOTALS IN EXCESS
OF ONE THIRD INCH...BUT LESS THAN ONE HALF INCH...WILL BE MOST
LIKELY OVER FAR SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA TONIGHT
INTO WEDNESDAY MORNING...AND OVER THE HIGHER TERRAIN OF SOUTH-
CENTRAL ARIZONA WEDNESDAY NIGHT. PRECIP AMOUNTS WILL VARY QUITE A
BIT FROM SITE TO SITE...SINCE CONVECTIVE SHOWERS AND A FEW
THUNDERSTORMS ARE EXPECTED.  STRONG RIDGING DEVELOPS BEHIND THE LOW
THURSDAY WHICH WILL QUICKLY BRING THE THREAT OF PRECIP TO AN END.

GFS/ECMWF IN GOOD AGREEMENT THAT A MUCH DIFFERENT AND RATHER
PERSISTENT LONG WAVE PATTERN WILL BECOME ESTABLISHED THIS WEEKEND
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. RIDGE AXIS SETS UP NEAR
120W (FAR WESTERN UNITED STATES) WHILE BROAD TROUGH WILL BE CENTERED
NEAR 90W (EASTERN UNITED STATES). THIS PATTERN PROMISES TO BRING DRY
CONDITIONS WITH DAYTIME HIGHS SEVERAL DEGREES ABOVE NORMAL THIS
WEEKEND INTO EARLY NEXT WEEK...WITH WARMEST DAYTIME HIGHS TOWARD THE
END OF THIS FORECAST PACKAGE (EARLY NEXT WEEK).

&&

.AVIATION...
KPHX AND KIWA...
THROUGH 11Z WED...SCT CLDS BASED NEAR 8 THSD WITH INCREASING HIGH
CLOUDS ABOVE. FROM 11Z TO 14Z...CLOUDS LOWERING AND BECOMING BKN 8
THSD MSL. 14Z WED THROUGH 23Z WED...BKN TO OVC CLDS BASED NEAR 5
THSD AGL WITH SCATTERED RAIN SHOWERS.

KIPL AND KBLH...
COLD FRONT APPROACHING THROUGH 14Z. CLDS LOWERING AND BECOMING BKN
TO OVC 4 TO 5 THSD FT AGL WITH SCT SHWRS AND ISOLATED THUNDERSTORMS.
VISIBILITY IN HEAVIER SHOWERS FALLING TO NEAR 3 MILES. AFT 14Z
CLOUDS BECOMING SCT TO OCNL BKN NEAR 5 THSD AGL WITH A FEW SHOWERS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY NIGHT THROUGH MONDAY...
SOME LINGERING SHOWERS ARE EXPECTED WEDNESDAY NIGHT...MAINLY EAST OF
PHOENIX. HIGH PRESSURE ALOFT FROM THE PACIFIC WILL BRING A RETURN TO
RELATIVELY DRIER AIR AND A RECOVERY OF TEMPERATURES THURSDAY AND
FRIDAY WITH FURTHER WARMING THIS COMING WEEKEND. MINIMUM RELATIVE
HUMIDITY IS EXPECTED TO GENERALLY REMAIN ABOVE 20 PERCENT WITH GOOD
TO EXCELLENT RECOVERY AT NIGHT. SOME BREEZINESS FROM THE NORTH AND
NORTHEAST IS EXPECTED THIS WEEKEND...ESPECIALLY DOWN THE LOWER
COLORADO RIVER VALLEY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 10 AM PST
     WEDNESDAY CAZ030.


&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ/DG
AVIATION...VASQUEZ
FIRE WEATHER...ELLIS