000 
FXUS65 KPSR 210909
AFDPSR
AZZ020>028-CAZ030>033-211745-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
210 AM MST THU MAR 21 2002

.SYNOPSIS...
A RIDGE OF HIGH PRESSURE OVER THE REGION WILL KEEP TEMPERATURES WELL 
ABOVE NORMAL TODAY AND FRIDAY. DAYTIME HIGHS WILL RANGE FROM 85 TO 
90 OVER MOST LOWER DESERT LOCATIONS. THE RIDGE IS FORECAST TO BREAK 
DOWN THIS WEEKEND AS A SERIES OF PACIFIC WEATHER SYSTEMS MOVE INTO 
THE WESTERN STATES...INCLUDING ARIZONA. BREEZY TO WINDY WEATHER 
...WITH A COOLING TREND...IS FORECAST SATURDAY THROUGH MONDAY...WITH 
DAYTIME HIGH TEMPERATURES EXPECTED TO BE A FEW DEGREES BELOW NORMAL 
BY MONDAY. TEMPERATURES WILL WARM TO SLIGHTLY ABOVE NORMAL BY THE 
MIDDLE OF NEXT WEEK AS WEAK HIGH PRESSURE DEVELOPS ALOFT. DRY 
CONDITIONS ARE ANTICIPATED THROUGH THE MIDDLE OF NEXT WEEK.


.DISCUSSION...
CLEAR SKIES CONTINUE OVER THE CWA EARLY THIS MORNING. CIRRUS WILL 
BEGIN TO SPREAD INTO THE AREA DURING THE DAY AS THE LARGE NORTHEAST 
PACIFIC UPPER LOW NUDGES EASTWARD. SATELLITE IMAGERY SHOWS THE RIDGE 
AMPLIFYING OVER THE WEST EVEN AS THE AXIS SHIFTS EASTWARD. AS A 
RESULT...THE MODELS SHOW WARMING OF THE 850 MB TEMPS FOR TODAY AND 
THIS IS CARRIED OVER IN THE GUIDANCE PRODUCTS FOR THE SURFACE TEMPS. 
THE NORTHEAST PACIFIC SYSTEM HAS EMBEDDED CIRCULATIONS ROTATING 
AROUND IT WHICH ARE BEING SUPPLIED BY THE SOUTHERN BRANCH OF THE 
POLAR JET. ON THE OTHER SIDE OF THE PACIFIC IS A LARGE VORTEX WHICH 
IS EJECTING LOW PRESSURE SYSTEMS ACROSS THE PACIFIC. 
MEANWHILE...DOWNSTREAM OF OUR RIDGE IS A DEEP UPPER LOW CENTERED 
OVER HUDSON BAY. 

THE PROGS SHOW THE RIDGE BEGINNING TO BREAK DOWN FRIDAY NIGHT AND 
SATURDAY AS THE SOUTHERN END OF THE NORTHEAST PACIFIC SYSTEM SWINGS 
INLAND. THE ETA AND NGM ARE QUITE SIMILAR TO EACH OTHER WHILE THE 
AVN IS FASTER AND DEEPER. THE DIFFERENCES ARE MOST NOTICEABLE FOR 
AREAS WELL TO OUR NORTHWEST. GIVEN THE PRESENCE OF THE LOW 
DOWNSTREAM...A SOMEWHAT SLOWER SOLUTION MIGHT BE BETTER. UKMET AND 
ECMWF ARE ALSO A BIT SLOWER THAN THE AVN/MRF. EITHER WAY...THE 
BREEZES WILL BE PICKING UP FRIDAY AND TEMPS WILL STILL BE QUITE 
WARM. WITH THE TROUGH FURTHER INLAND...STRONGER WINDS CAN BE 
EXPECTED SATURDAY WITH SOME NOTICEABLE COOLING. SUCCESIVE SHORT 
WAVES WITHIN THE TROUGH WILL LEAD TO SOME ADDITIONAL COOLING SUNDAY. 
A RIDGE BEGINS TO BUILD INTO THE CWA MONDAY...PROBABLY A BIT SLOWER 
THAN DEPICTED BY AVN/MRF. WITH THE BUILDING RIDGE...TUESDAY TEMPS 
WILL BE WARMER. AVN/MRF MORE AGRESSIVE WITH AMPLITUDE OF RIDGE THAN 
OTHER MEDIUM RANGE PROGS INCLUDING MRF ENSEMBLE MEAN. FOR 
WEDNESDAY...AVN/MRF HAS ANOTHER TROUGH MOVING INTO THE WEST WHICH 
WOULD LOWER OUR TEMPS. AN EXTRAPOLATION OF THE UKMET WOULD SUPPORT 
THIS AS WELL. HOWEVER...THE ECMWF AND ENSEMBLE MEAN DEPICT MERELY A 
FLATTENING OF THE RIDGE. THUS WILL KEEP WEDNESDAY TEMPS SIMILAR TO 
TUESDAY. PROGS STILL DEPICT DRY CONDITIONS THROUGH WEDNESDAY.  

.PSR...NONE.

JAMISON