FXUS65 KPSR 110408
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
908 PM MST FRI FEB 10 2012

.SYNOPSIS... 
THE HIGH PRESSURE SYSTEM RESPONSIBLE FOR CLEAR SKIES AND WARM 
TEMPERATURES WILL WEAKEN EARLY SATURDAY MORNING AS ANOTHER PACIFIC 
WEATHER SYSTEM APPROACHES THE REGION AND MOVES ACROSS ARIZONA ON 
SUNDAY. COOLER TEMPERATURES ARE EXPECTED THIS WEEKEND...WITH A 
SLIGHT CHANCE OF SHOWERS OVER SOUTH CENTRAL ARIZONA ON SUNDAY. DRY 
WEATHER WILL DEVELOP MONDAY...HOWEVER ANOTHER IN A SERIES OF WEATHER 
SYSTEMS WILL MOVE ACROSS THE REGION TUESDAY AND WEDNESDAY. A THREAT 
OF SHOWERS AND COOLER TEMPERATURES WILL DEVELOP TUESDAY AND 
WEDNESDAY. CLEAR AND WARMER WEATHER WILL DEVELOP AT THE END OF NEXT 
WEEK.

&&

.DISCUSSION...
MID EVENING WATER VAPOR AND IR SATELLITE IMAGERY SHOWS A WEAKENING 
RIDGE AXIS ACROSS WESTERN ARIZONA...WITH A SMALL PLUME OF MOISTURE 
MOVING THROUGH SOUTHERN CALIFORNIA. SO FAR SKIES REMAIN CLEAR ACROSS 
THE FORECAST AREA BUT BASED ON SATELLITE TRENDS I WOULD EXPECT SOME 
CLOUDINESS TO ARRIVE OVERNIGHT. THIS CONFIRMS WHAT IS ALREADY IN THE 
FORECAST AND NO CHANGES TO THE SKY GRIDS APPEAR TO BE NECESSARY AT 
THIS POINT. 00Z NAM AND 18Z HIRES WRF GUIDANCE ARE IN AND BOTH 
SUGGEST THE WINDIEST SPOTS WILL BE LOCATED ACROSS SOUTHEAST 
CALIFORNIA SATURDAY AFTERNOON. THE TYPICALLY WINDY SPOTS ACROSS FAR 
SOUTHWEST IMPERIAL COUNTY COULD APPROACH WIND ADVISORY CRITERIA FOR 
A BRIEF TIME LATE IN THE AFTERNOON...BUT ELSEWHERE WINDS SHOULD 
REMAIN AROUND 20-25MPH. FORECAST IS IN GOOD SHAPE...NO MAJOR CHANGES 
THIS EVENING.

&&

.PREVIOUS DISCUSSION...

TONIGHT THROUGH SUNDAY...
A HIGH PRESSURE SYSTEM OVER THE REGION WILL WEAKEN TONIGHT AND MOVE 
EAST AS A PACIFIC WEATHER DISTURBANCE APPROACHES. THE WEATHER 
DISTURBANCE WILL MOVE ACROSS AZ ON SUNDAY. AGAIN...SUNDAYS SYSTEM 
IS RELATIVELY DRY...HOWEVER THE EUROPEAN MODEL IS SLIGHTLY STRONGER 
AND SLIGHTLY WETTER THAN THE GFS MODEL...SUGGESTING THAT PERHAPS A 
SLIGHT CHANCE OF AFTERNOON INSTABILITY SHOWERS COULD DEVELOP ACROSS 
PORTIONS OF SOUTH CENTRAL AZ ON SUNDAY. CLEARING SUNDAY NIGHT.

MONDAY...
THERE WILL BE A BREAK THE PATTERN MONDAY...WITH DRY WEATHER AND NEAR 
NORMAL TEMPERATURES...BEFORE THE NEXT IN A SERIES OF STRONGER 
DISTURBANCES MOVE INTO THE REGION TUESDAY THROUGH WEDNESDAY. 

TUESDAY AND WEDNESDAY...
A STRONGER PACIFIC WEATHER DISTURBANCE IS FORECAST TO MOVE INTO THE 
REGION TUESDAY AND WEDNESDAY. AGAIN...THERE IS SIGNIFICANT NUMERICAL 
MODEL DISAGREEMENTS. THE EUROPEAN AND GFS MODELS HAVE MUCH DIFFERENT 
TIMING AND INTENSITY ISSUES...WHICH HAS BEEN ONGOING FOR SEVERAL 
DAYS NOW. IN NCEPS EXTENDED FORECAST DISCUSSION THEY MENTION LOW 
MODEL CONFIDENCE THIS PERIOD...HOWEVER THEY SLIGHTLY PREFER THE 
EUROPEAN ENSEMBLE FORECASTS...AND HAVE LEANED ON THEM EXCLUSIVELY 
FOR THE NEXT 7 DAYS.  WE ARE JUST PRIVY TO THE EUROPEAN ENSEMBLE 
MEAN...HOWEVER DUE TO THE LOW CONFIDENCE ASPECT...WE CONTINUE TO 
BROAD BRUSH THE FORECASTS WITH LOW END PRECIP THREATS LATE MONDAY 
NIGHT THROUGH WEDNESDAY EVENING.  HOWEVER THE EUROPEAN OPERATIONAL 
MODEL DOES FOCUS ON WEDNESDAY A THE BEST CHANCE OF SHOWERS FOR 
SOUTHWEST AND SOUTH CENTRAL AZ...INCLUDING PHOENIX.

THURSDAY AND FRIDAY...
DRY AND WARMER.
 
&&

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

CLOUDS WILL GRADUALLY INCREASE THROUGH THE DAY SATURDAY WITH MAINLY 
MID/HIGH CLOUDS EXPECTED BY 12Z. TYPICAL DIURNAL WIND PATTERNS AT 
KIWA/KPHX BUT WINDS WILL BE QUITE BREEZY OUT WEST. STRONGEST WINDS 
AT IPL WITH GUSTS TO 20KTS POSSIBLE...LIGHTER WINDS AT BLH. WINDS 
WILL CALM DOWN AT ALL SITES AFTER 03Z SATURDAY BUT CLOUDS WILL 
REMAIN THROUGH SUNDAY MORNING. 

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&& 

.FIRE WEATHER... 
SUNDAY THROUGH THURSDAY... 
COOLER TEMPERATURES AND HIGHER HUMIDITY LEVELS AREA EXPECTED AS A 
SERIES OF LOW PRESSURE SYSTEMS MOVE THROUGH THE REGION. THE WEATHER 
PATTERN WILL REMAIN COOL AND UNSETTLED...WITH PRECIPITATION CHANCES  
LINGERING THROUGH WEDNESDAY...THE BEST CHANCES IN THE HIGHER TERRAIN 
AREAS NORTH AND EAST OF PHOENIX. DRIER CONDITIONS AND A SLOW GRADUAL 
WARMING TREND WILL TAKE PLACE ACROSS SOUTHEAST CALIFORNIA AND THE 
SOUTHWEST DESERTS OF ARIZONA FROM THURSDAY INTO NEXT WEEKEND. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ 
AVIATION...LEINS
FIRE WEATHER...MEYERS