158
FXUS65 KPSR 030349
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
848 PM MST WED OCT 2 2013

.SYNOPSIS...
A WEATHER SYSTEM MOVING THROUGH THE GREAT BASIN STATES TO THE NORTH
WILL GENERATE BREEZY CONDITIONS AND COOLER TEMPERATURES BEGINNING
THURSDAY FOR OUR AREA. THE STRONGEST WINDS ARE EXPECTED ACROSS
SOUTHEAST CALIFORNIA AND THE COLORADO RIVER VALLEY. BY
MONDAY...TEMPERATURES WILL CLIMB BACK TO NORMAL READINGS. ANOTHER
PASSING WEATHER SYSTEM COULD DROP TEMPERATURES AGAIN BY MIDWEEK.

&&

.DISCUSSION...
CLEAR SKIES AND GENERALLY LIGHT SURFACE WINDS CONTINUED ACROSS MUCH
OF THE SOUTH CENTRAL ARIZONA DESERTS THIS AFTERNOON AND EARLY
EVENING. THE ONLY EXCEPTION WOULD BE SOUTHERLY SURFACE WINDS ACROSS
MUCH OF THE SOUTHEAST CALIFORNIA AND THE LOWER COLORADO RIVER
VALLEY...WITH SOME READINGS JUST OVER THE 10 MPH MARK. LARGE AREA OF
LOW PRESSURE FINALLY PUSHING ON-SHORE INTO OREGON AND WASHINGTON
STATES THIS EVENING...WITH TROUGHING TRAILING DOWN INTO THE SOUTHERN
CALIFORNIA. THE PARENT LOW PRESSURE SYSTEM WILL STAY MOSTLY NORTH OF
OUR AREA AS IT MOVES EAST...BRUSHING THROUGH THE FOUR CORNERS REGION
THROUGH THE WEEKEND. SURFACE COOL FRONT STILL FORECAST TO DROP NORTH
TO SOUTH FRIDAY WITH INCREASING SURFACE WINDS BEGINNING AS EARLY AS
THURSDAY. CONCERN REMAINS REGARDING CRITICAL FIRE WEATHER CONDITIONS
ACROSS MUCH OF THE SOUTHEAST CALIFORNIA AND A FIRE WEATHER WATCH
REMAINS IN EFFECT AT THIS TIME. NO SIGNIFICANT CHANGES PLANNED FOR
THE FORECAST PACKAGE THIS EVENING.

&&

.PREVIOUS DISCUSSION /ISSUED AT 228 PM MST/PDT/...
AN APPROACHING TROUGH WILL BEGIN TO INCREASE WINDS STARTING EARLY
THURSDAY THROUGH SUNDAY AND DROP TEMPS A BIT WITH A RETURN TO NEAR
NORMAL TEMPS BY TUESDAY. ANOTHER PASSING TROUGH MAY IMPACT THE
REGION BY WEDNESDAY BRINGING ANOTHER PERIOD OF BREEZY CONDITIONS AND
POSSIBLY DROP TEMPS A BIT. NO PRECIPITATION EXPECTED THROUGH THE
FORECAST PERIOD.

MODELS AGREE ON TIMING AND STRENGTH OF THE LOW PRESSURE SYSTEM
MOVING INTO THE NORTHWEST COAST AND DEEPENING IN THE ROCKIES BY
FRIDAY MORNING. THIS SYSTEM WILL TIGHTEN THE GRADIENT...MOST
NOTICEABLY IN NORTHERN ARIZONA AND PRODUCE TWO TO THREE DAYS OF
INCREASED WINDS ACROSS THE REGION. BY SUNDAY WEAK HIGH PRESSURE WILL
SET BACK IN AND ALLOW TEMPS TO RECOVER TO NEAR NORMAL AND LIGHT
WINDS TO RETURN. BY TUESDAY EVENING ANOTHER SHORT WAVE WILL APPROACH
ARIZONA AND LIKELY DROP TEMPS AND PRODUCE WINDS AGAIN ACROSS THE
REGION. THE EURO SHOWS THIS SYSTEM TO BE OF LARGER
SCALE...STRETCHING SOUTH FROM A LOW PRESSURE IN IDAHO WHEREAS THE
GFS ONLY HAS IT AS A SMALL SCALE SHORT WAVE. EITHER SOLUTION IS
DOUBTFUL TO BRING US ANY PRECIP BUT COULD AFFECT WHEN AND HOW MUCH
WIND WE SEE.

EARLY MORNING FORECAST DISCUSSION /ISSUED 340 AM MST/PDT/
WEDNESDAY THROUGH FRIDAY...
WATER VAPOR IMAGERY SHOWS AN UPPER TROUGH AXIS APPROACHING THE WEST
COAST WITH THE ASSOCIATED UPPER LOW CENTER NEAR VANCOUVER ISLAND.
UPSTREAM IS A HIGH AMPLITUDE RIDGE. THE UPSTREAM RIDGING WILL HELP
DRIVE THE LOW PRESSURE SYSTEM SOUTHEASTWARD ACROSS THE PACIFIC
NORTHWEST STATES TODAY AND INTO THE GREAT BASIN THURSDAY.
SUBTROPICAL HIGH PRESSURE OVER MEXICO WILL HELP KEEP THE SYSTEM FROM
PLOWING THOUGH THE SOUTHWEST STATES BUT WE WILL FEEL ITS AFFECTS. A
DRY COOL FRONT WILL MOVE THROUGH OUR FORECAST AREA THURSDAY NIGHT
AND FRIDAY. THIS WILL LEAD TO BREEZY TO WINDY CONDITIONS FROM THE
NORTH AND NORTHEAST BEHIND THE FRONT...MOST NOTABLY OVER SOUTHEAST
CALIFORNIA AND FAR SOUTHWEST ARIZONA. WE MIGHT TOUCH WIND ADVISORY
THRESHOLDS THERE. TOO EARLY AT THIS POINT TO ISSUE AN ADVISORY BUT
THERE IS HIGHER CONFIDENCE IN RED FLAG CONDITIONS AND THUS A WATCH
HAS BEEN ISSUED FOR SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY FRIDAY. THE APPROACH AND PASSAGE OF THE SYSTEM WILL
LEAD TO SOME COOLER TEMPERATURES AS WELL. COOLING BEGINS THURSDAY
WITH THE WEAKENING OF THE RIDGE WITH SOME ADDITIONAL COOLING FRIDAY
BEHIND THE FRONT. ANTICIPATE HIGHS ON FRIDAY TO BE ROUGHLY 5-10
DEGREES COOLER THAN TODAY...MOST NOTICEABLY OVER SOUTHEAST
CALIFORNIA AND SOUTHWEST ARIZONA. MIN TEMPS MAY NOT SHOW A LOT OF
COOLING DUE TO MORE MIXING.

SATURDAY THROUGH TUESDAY...
A TRAILING SHORT WAVE WILL MOVE THROUGH THE NORTHEASTERN HALF OF
ARIZONA FRIDAY NIGHT AND SATURDAY WHICH WILL ADD SOME SUBTLE COOLING
TO SOUTH-CENTRAL ARIZONA. ANTICIPATE BREEZY TO LOCALLY WINDY
CONDITIONS SATURDAY...AGAIN MORE NOTICEABLY OVER OUR WESTERN AREAS
EXCEPT FOR SOME LOCAL FOOTHILL AREAS THAT ARE PRONE TO NORTHEASTERLY
DOWNSLOPE WINDS. RIDGING BUILDS INTO THE REGION EARLY NEXT WEEK FOR
WARMER DAYTIME TEMPS SUNDAY AND MONDAY BUT NOT ABOVE NORMAL. MIN
TEMPS MIGHT NOT BE WARMER DUE TO LESS MIXING. GFS AND ECWMF SHOW A
RIDGE AMPLIFYING OVER THE NORTHEAST PACIFIC BUT THEIR SOLUTIONS VARY
GREATLY ON THE STRENGTH AND TIMING OF THE DOWNSTREAM SHORT WAVE ON
TUESDAY. THE WEAKER GFS IS SUPPORTED BY THE GEFS MEAN. THE ECWMF
CONTINUES TO SHOW A SLOWER AND DEEPER SYSTEM BUT ITS ENSEMBLE MEAN
SUPPORTS A WEAKER SYSTEM. FOR NOW...WILL SHOW LITTLE CHANGE TUESDAY
UNTIL THE PICTURE BECOMES CLEARER. EVEN THE STRONGER ECWMF SOLUTION
WOULD STILL BE DRY FOR OUR AREA.

&&

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

MOSTLY CLEAR SKIES...GENERALLY LIGHT DIURNALLY DRIVEN WIND PATTERNS
AND DRY CONDITIONS EXPECTED FOR THE TERMINALS THROUGH THURSDAY LATE
AFTERNOON. TOWARDS THE LATTER PART OF THE TAF PERIOD...WINDS FOR
KIPL AND KBLH WILL BEGIN TO INCREASE...AT TIMES 12 KTS OR
GREATER...AHEAD OF WEATHER SYSTEM MOVING TO THE NORTH.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH WEDNESDAY...
DRY AND WINDY CONDITIONS WILL ARRIVE ACROSS SOUTHEAST CALIFORNIA AND
THE LOWER COLORADO RIVER VALLEY ON FRIDAY. FORECAST THINKING REMAINS
ON TRACK...ONLY CHANGE WAS TO INCLUDE JOSHUA TREE NATIONAL PARK IN
THE FIRE WX WATCH. OTHERWISE THE FORECAST REMAINS THE SAME WITH
CRITICAL FIRE WEATHER CONDITIONS POSSIBLE FRIDAY...WITH DECREASING
WINDS SATURDAY INTO EARLY NEXT WEEK. DESPITE DECREASING
WINDS...HUMIDITIES WILL REMAIN IN THE SINGLE DIGITS EACH AFTERNOON
WITH POOR OVERNIGHT RECOVERY EXPECTED ACROSS THE ENTIRE REGION.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FIRE WEATHER WATCH FOR FRIDAY MORNING THROUGH FRIDAY EVENING
     AZZ020-025.

CA...FIRE WEATHER WATCH FOR FRIDAY MORNING THROUGH FRIDAY EVENING
     CAZ030>033.

&&

$$

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DISCUSSION...NOLTE
PREVIOUS DISCUSSIONS...WATERS/AJ
AVIATION...NOLTE
FIRE WEATHER...LEINS