907 
FXUS65 KPSR 271020
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
320 PM MST MON APR 27 2009

.SYNOPSIS...
CLOUDS WILL BE ON THE INCREASE TODAY AS A WEAK AREA OF LOW PRESSURE 
OFF THE SOUTHERN CALIFORNIA COAST MOVES EAST ACROSS THE FORECAST 
AREA. WARMER CONDITIONS ARE EXPECTED DESPITE THE CLOUDS WITH HIGH 
TEMPERATURES IN THE UPPER 80S. THE WARMING TREND WILL CONTINUE 
THROUGH THE WEEK...WITH THE WARMEST TEMPERATURES EXPECTED THU OR FRI 
AS HIGH PRESSURE BUILDS ACROSS THE INTERMOUNTAIN WEST.

&&

.DISCUSSION...
ONE SHORT WAVE TROUGH ACROSS CO WILL EJECT NORTHEASTWARD TODAY WHILE 
ANOTHER DIVES SOUTH ALONG THE PACIFIC NORTHWEST COAST. IN BETWEEN 
THESE TWO SYSTEMS...HEIGHT RISES NEAR THE FOUR CORNERS WILL EQUATE 
TO ROUGHLY A 5 DEGREE INCREASE (COMPARED TO SUN) IN MAX TEMPS. 
MEANWHILE IN THE SOUTHERN STREAM...A JET MAX OFF THE SOUTHERN CA 
COAST WILL PRODUCE AN INCREASE IN CIRRUS THROUGHOUT THE DAY.

WARMING TREND WILL CONTINUE THROUGH THE WEEK AS A SERIES OF VORTS 
ACROSS THE PACIFIC NORTHWEST EVOLVE INTO A LARGER 
VORTEX...GENERATING A WARM DRY WESTERLY FLOW ACROSS THE DESERT 
SOUTHWEST. THIS LOW WILL ULTIMATELY FILL WHILE SLIDING EASTWARD 
LATE IN THE WEEK. WARMEST DAY LOOKS TO BE THU OR FRI WITH THE MODELS 
(PREFERENCE AGAIN TOWARDS THE ECMWF) DEPICTING A RIDGE BUILDING 
ACROSS THE WESTERN CONUS. MEX TEMPS IN THE EXTENDED HAVE BOUNCED 
AROUND SOMEWHAT OVER THE PAST FEW DAYS...THOUGH LATEST RUN APPEARS 
REASONABLE WITH HIGH TEMPS PEAKING IN THE MID 90S IN THE LOWER 
DESERTS...OR ROUGHLY 5 DEGREES ABOVE AVERAGE.

CONFIDENCE IS INCREASING FOR NEXT WEEKEND WITH A TROUGH MOVING EAST 
OFF THE PACIFIC. IT IS UNLIKELY THIS SYSTEM WILL HAVE A SIGNIFICANT 
IMPACT THIS FAR SOUTH. NEVERTHELESS...LATEST FCST REFLECTS A SLIGHT 
INCREASE IN POPS...ALBEIT LESS THAN 10 PERCENT.

&&

.AVIATION...
SOUTH-CENTRAL DESERTS INCLUDING KPHX AND KIWA...
WINDS GENLY FROM THE WEST THIS EVENING LESS THAN 15 KTS...BECOMING 
LIGHT DIURNAL BY MIDNIGHT. EXPECT WINDS TO BECOME SLY BY LATE 
MORNING THEN BACK TO THE SW OR W 6-10 KTS BY 21Z MONDAY. CLEAR SKIES 
ON TAP THIS EVENING WITH SOME INCREASE IN HIGH CLOUDS BY SUNRISE. 
INCREASING AND THICKENING HIGH CLOUDS MONDAY...WITH SOME OVC CIGS 
AOA 20K FEET BY AFTERNOON. VFR CONDITIONS ALL AIRFIELDS NEXT 24 
HOURS.

KIPL...
WIND EXPECTED TO GENERALLY BE FROM THE WEST TONIGHT THRU LATE MONDAY 
MORNING...GENLY LESS THAN 10 KTS. COULD SEE WINDS BACK AROUND TO THE 
SOUTHEAST AFTER 19Z MONDAY...AT 6-10KT. CLEAR SKIES THIS EVE...BUT 
THEN INCREASING HIGH CLOUDS AFTER MIDNIGHT...WITH BKN TO OVC CIGS 
AOA 20K FEET BY MID DAY MONDAY. VFR CONDITIONS NEXT 24 HOURS.

KBLH...
WINDS SHOULD TEND TO FAVOR THE SOUTH LESS THAN 10KT THIS EVE...THEN 
BECOME LIGHT VARIABLE AFTER MIDNIGHT. WINDS WILL PICK UP AGAIN FROM 
THE SOUTH OR SOUTHEAST BY 18Z MONDAY...WITH SOME AFTERNOON GUSTS TO 
18KT POSSIBLE. EXPECT CLEAR SKIES THIS EVE...THEN GRADUALLY 
INCREASING HIGH CLOUDS AFTER MIDNIGHT WITH BKN-OVC CIGS AOA 20K FEET 
BY 18Z MONDAY. VFR CONDITIONS NEXT 24 HOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
VERY DRY WEATHER IS EXPECTED TO CONTINUE WITH MINIMUM AFTERNOON 
RELATIVE HUMIDITY GENERALLY BELOW 15 PERCENT...AND IN THE SINGLE 
DIGITS IN ALL BUT THE HIGHEST TERRAIN THROUGH FRIDAY. TEMPERATURES 
ARE ANTICIPATED TO CLIMB ABOVE AVERAGE WITH HIGHS IN THE 90S IN THE 
LOWER ELEVATIONS. TYPICAL AFTERNOON BREEZINESS CAN BE EXPECTED...
EXCEPT WINDS FROM THE SOUTHWEST MAY INCREASE SATURDAY AFTERNOON AS 
THE DRY SOUTHERN END OF A PACIFIC LOW PRESSURE SYSTEM MOVES INTO THE 
AREA.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...HIRSCH
AVIATION...CB
FIRE WEATHER...ELLIS