496 
FXUS65 KPSR 221156
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
455 AM MST TUE APR 22 2014

...UPDATED AVIATION AND FIRE WEATHER...

.SYNOPSIS...
BREEZY TO WINDY CONDITIONS WILL DEVELOP OVER MUCH OF THE AREA THIS 
AFTERNOON INTO WEDNESDAY AS A DRY WEATHER SYSTEM PASSES TO THE 
NORTH. TEMPERATURES WILL FALL IN RESPONSE TO THIS WEATHER SYSTEM... 
AND LOWER TO AROUND SEASONAL NORMALS BY WEDNESDAY.  A SLIGHT WARMING 
TREND WILL OCCUR THURSDAY INTO FRIDAY AS HIGHER PRESSURE ALOFT 
RETURNS TO THE AREA...BEFORE ANOTHER VIGOROUS PACIFIC UPPER LEVEL 
LOW PRESSURE SYSTEM BRINGS SIGNIFICANT WIND AND COOLING TO THE AREA 
OVER THE WEEKEND. 

&&

.DISCUSSION...
WATER VAPOR IMAGERY REVEALS OUR NEXT WEATHER SYSTEM CURRENTLY MOVING 
INLAND ALONG THE WEST COAST...THE CENTER OF THE 533DM LOW SPINNING 
IN THE PACIFIC WEST OF BRITISH COLUMBIA...THE SOUTHERN EXTENT OF THE 
TROUGH IMPACTING CENTRAL AND NORTHERN CALIFORNIA. FURTHER SOUTH AND 
AHEAD OF THE TROUGH...BANDS OF HIGH CLOUDS ARE STREAMING ACROSS 
SOUTHEAST CALIFORNIA INTO NEVADA AND WESTERN ARIZONA THIS MORNING. 
MID AND LOWER LEVEL PRESSURE GRADIENTS CONTINUE TO TIGHTEN...AND THE 
LOW LEVEL WIND FIELDS ARE BEGINNING TO RESPOND THROUGH PORTIONS OF 
THE SIERRA NEVADA IN CALIFORNIA WITH SOME GUSTS UP TO 30 MPH NOTED 
IN SURFACE OBSERVATIONS. 

THE INFLUENCE OF THE TROUGH WILL BE FELT ACROSS OUR CWA LATER THIS 
AFTERNOON AND EVENING...WITH STRONG GUSTY WINDS OF 20-25 MPH AND 
LOCAL GUSTS TO 35 MPH COMMON ACROSS SOUTHEAST CALIFORNIA AND 
SOUTHWEST ARIZONA. SOME LOCATIONS IN AND AROUND THE IMPERIAL 
VALLEY/EL CENTRO CA...JOSHUA TREE NATIONAL PARK...AND OTHER HIGHER 
TERRAIN AREAS IN LA PAZ COUNTY AZ MAY EXPERIENCE STRONGER WIND GUSTS 
ALONG WITH AREAS OF BLOWING DUST/SAND. RIGHT NOW...FORECAST WIND 
SPEEDS ARE NOT MEETING WIND ADVISORY CRITERIA...BUT IT WILL BE 
SOMETHING TO MONITOR. 

GIVEN THE DRY NATURE OF THE TROUGH AND FRONTAL PASSAGE...THE WINDS 
WILL ONLY CONTRIBUTE TO DANGEROUS FIRE WEATHER CONDITIONS. AS 
SUCH...A RED FLAG WARNING IS IN EFFECT FROM 2 TO 8 PM TODAY FOR 
SOUTHWEST ARIZONA INCLUDING THE LOWER COLORADO RIVER VALLEY. THE 
SYSTEM WILL ALSO BRING 8-10 DEGREES OF COOLING...LOWERING DAYTIME 
TEMPERATURES BACK INTO THE MID TO UPPER 80S OVER THE LOWER DESERTS. 

SHORTWAVE RIDGING COMMENCES THURSDAY...WITH 500MB HEIGHTS REBOUNDING 
TO NEAR 576DM OVER SOUTHERN CALIFORNIA AND SOUTH-CENTRAL ARIZONA BY 
FRIDAY. HOWEVER...ANOTHER POTENT UPPER LEVEL TROUGH WILL MOVE INTO 
THE REGION LATE FRIDAY AND ONCE AGAIN BRING ANOTHER ROUND OF COOLER 
TEMPERATURES AND INCREASED WINDS THIS WEEKEND.

THE GFS/ECMWF ARE NOW IN MUCH BETTER AGREEMENT WITH THIS NEXT 
SYSTEM...EVEN THOUGH THERE ARE STILL SOME TIMING DIFFERENCES. BOTH 
PLACE A 542-556DM UPPER LEVEL LOW/OPEN WAVE OVER NEVADA BY SATURDAY 
MORNING. THE OPERATIONAL GEM MORE ALIGNED WITH THE GFS AND ECMWF... 
BUT MAINTAINING A CLOSED LOW SOLUTION. AT THIS TIME...UNLESS THE 
SYSTEM DIGS EVEN DEEPER WEST OF CALIFORNIA...ANY SOLUTION WILL 
REMAIN CONSIDERABLY DRY WITH PRECIPITATION CHANCES SLIGHT/SLIM FOR 
OUR FORECAST AREA. WITH LOWER HEIGHTS AND A TIGHTENED GRADIENT OF 
555-564DM SPLAYED ACROSS SOUTHEAST CALIFORNIA AND SOUTH-CENTRAL 
ARIZONA...THE FORECAST WILL CONTINUE TO DROP DAYTIME TEMPERATURES 
BACK INTO THE LOW 80S...ALONG WITH BREEZY TO WINDY CONDITIONS AGAIN 
SATURDAY AND SUNDAY. 

&&

.AVIATION... 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
WINDS WILL BE THE MAIN AVIATION CONCERN THROUGH WEDNESDAY 
MORNING...WITH INCREASING SPEEDS AND FREQUENT GUSTS DEVELOPING THIS 
AFTERNOON THROUGH EARLY EVENING. THE LARGEST PROBLEM MAY BE A 
PROLONGED SEVERAL HOUR PERIOD OF A SOUTHERLY CROSS COMPONENT LATE 
MORNING/EARLY AFTERNOON. ANY GUSTS ASSOCIATED WITH A DUE SOUTH WIND 
SHOULD REMAIN AOB 20KT...BEFORE THE DIRECTION VEERS TOWARDS A MORE 
SWLY/WLY DIRECTION LATER IN THE AFTERNOON. GUSTS SHOULD SUBSIDE 
LATER THIS EVENING...HOWEVER FORECAST CONFIDENCE IN TIMING THE LOSS 
OF GUSTINESS IS LOW. 

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...  
STRONG SFC WINDS WILL BE THE LARGEST AVIATION CONCERN ACROSS SE 
CALIFORNIA THIS AFTERNOON AND EVENING. A WLY COMPONENT AT KIPL AND 
SLY WIND AT KBLH WILL BOTH BEGIN GUSTING ABOVE 20KT BY LATE MORNING. 
EVENTUALLY WINDS AT BOTH AIRFIELDS WILL BECOMING SWLY BY LATE 
AFTERNOON WITH FREQUENT GUSTS TO AROUND 30KT DEVELOPING. NOCTURNAL 
DECOUPLING SHOULD ALLOW GUSTS TO SUBSIDE LATER THIS 
EVENING...HOWEVER THE FORECAST CONFIDENCE IN TIMING WHEN WIND SPEEDS 
BEGIN TO DECREASE IS LOW. 

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.  

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
WEAK HIGH PRESSURE AND RELATIVELY LIGHT WINDS THURSDAY WILL BE 
REPLACED BY A STRONG PACIFIC WEATHER SYSTEM MOVING NORTH OF THE 
DISTRICT FRIDAY AND SATURDAY. THIS SYSTEM WILL ALLOW WINDS TO 
INCREASE IN A SIMILAR FASHION TO TODAY...YIELDING AN ELEVATED FIRE 
DANGER WITH HUMIDITY LEVELS FALLING INTO THE LOWER TEENS AND WIND 
GUSTS APPROACHING 30 MPH. MORE TRANQUIL WEATHER CONDITIONS ARE 
LIKELY NEXT WEEK WITH A WARMING TREND...ALBEIT WITH MINIMUM HUMIDITY 
LEVELS FALLING BACK INTO THE SINGLE DIGITS AND ONLY FAIR OVERNIGHT 
RECOVERY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...RED FLAG WARNING TUESDAY AFTERNOON AND EVENING FOR FIRE ZONES 
AZZ131 AND AZZ132...2 PM UNTIL 8 PM.

CA...RED FLAG WARNING TUESDAY AFTERNOON AND EVENING FOR FIRE ZONE 
CAZ231...2 PM UNTIL 8 PM.

&&

$$

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DISCUSSION...MEYERS
AVIATION...MO
FIRE WEATHER...MO