000 
FXUS65 KPSR 110440
AFDPSR
AZZ020>028-CAZ030>033-111045-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION 
NATIONAL WEATHER SERVICE PHOENIX AZ
940 PM MST FRI MAY 10 2002

.SYNOPSIS...
WINDY CONDITIONS...WITH SOME BLOWING DESERT SAND AND DUST...ARE
FORECAST THROUGH THIS EVENING AS A LOW PRESSURE SYSTEM FROM NEVADA 
APPROACHES. THE DRY SOUTHERN END OF THIS SYSTEM WILL MOVE EAST 
ACROSS ARIZONA WITH SOME COOLING AND BREEZY CONDITIONS SATURDAY. 
STRONG HIGH PRESSURE ALOFT FROM THE SOUTHWEST WILL MOVE EAST ACROSS 
THE SOUTHWESTERN UNITED STATES WITH SIGNIFICANTLY WARMER WEATHER 
EARLY NEXT WEEK. ANOTHER WEAKER PACIFIC LOW PRESSURE SYSTEM WILL 
RESULT IN PARTLY CLOUDY SKIES TUESDAY AND WEDNESDAY...AND DROP 
TEMPERATURES SOMEWHAT LATE NEXT WEEK.

.DISCUSSION...
A RATHER STRONG YET DRY LOW PRESSURE SYSTEM CONTINUED TO DEVELOP 
OVER THE GREAT BASIN TODAY...AND AS OF THIS EVENING THE MAIN UPPER 
LOW WAS LOCATED OVER WESTERN AND CENTRAL NV...WITH H5 TEMPS OF MINUS 
25C. AZ WAS ON THE SERN EDGE OF THIS LOW...UNDER A RATHER STRONG DRY 
SWLY TO WLY WINDFLOW. GOES PWAT IMAGERY AND PLOT DATA SHOW HOW DRY 
AZ IS ATTM...AND SURFACE DEWPOINTS OVER SRN AZ MOSTLY ARE IN THE 
TEENS AND 20S...WITH SOME MID 30S SEEN OVER FAR SERN CA. IR 
SATELLITE IMAGERY DEPICTS VIRTUALLY CLEAR SKIES STATEWIDE AT 9 PM. 
STRONG GRADIENTS ASSOCD WITH THIS APPROACHING LOW CAUSED BREEZY TO 
WINDY CONDITIONS THIS AFTERNOON AND EVENING...WITH GUSTS OVER 30 MPH 
COMMON OVER THE SRN AZ DESERTS EARLIER...AND SOME OF THESE STRONGER 
GUSTS CAUSED BLOWING DUST PROBLEMS EARLIER THIS AFTERNOON IN THE 
CASA GRANDE AREA. THIS PROMPTED THE ISSUANCE OF A BLOWING DUST 
WARNING FOR THAT AREA...MAINLY SOUTH OF THE GILA RIVER...WITH ISOLD 
SPOTS SEEING VSBYS GOING DOWN TO NEAR ZERO MILES AT TIMES. AS OF 8 
PM MOST OF THE WINDS OVER THE SCNTRL AZ DESERTS HAD DROPPED OFF TO 
BELOW 25 MPH AND THUS THE WARNING WAS ALLOWED TO EXPIRE. STRONGER 
WINDS WERE SEEN OVER SERN CA...MAINLY IN THE IMPERIAL AREA...AND AS 
OF 9 PM GUSTS FROM 35 TO AROUND 40 MPH WERE BEING RECORDED AT EL 
CENTRO ...IMPERIAL AND TWENTY NINE PALMS NEAR JOSHUA TREE NATIONAL 
PARK. RATHER TIGHT SURFACE GRADIENT STILL EXISTS IN THAT AREA...AND 
IS KEEPING THE WINDS GOING STRONG. WIND ADVISORY REMAINS IN EFFECT 
FOR OUR CA ZONES TIL 11 PM TONIGHT...AND AT 9 PM ISSUED A FOLLOW UP 
STATEMENT ON THIS WIND EVENT. EXPECT WINDS TO TAPER OFF IN THE ADVY 
AREA BY MIDNIGHT OR SHORTLY THEREAFTER AS THE GRADIENTS RELAX. UPPER 
LOW FORECAST BY ETA AND NGM TO KEEP MOVING ESEWD NEXT 24 HOURS WITH 
THE UPPER LOW INTO FAR NRN AZ AND UT BY SAT AFTN/EVE. GRADIENTS NOT 
QUITE AS STRONG TOMORROW SO THERE WILL BE LESS WIND...BUT CERTAINLY 
THERE WILL BE ENOUGH FOR BREEZY CONDITIONS MOSTLY PLACES BY 
AFTERNOON. VERY DRY ATMOSPHERE CONTINUES...AS OUR AREA REMAINS ON 
THE SOUTHERN PERIPHERY OF THIS LOW...WHICH IS ALMOST ALWAYS A DRY 
SCENARIO FOR US. THUS GENLY CLEAR SKIES WILL CONTINUE TONIGHT AND 
SUNNY SKIES AWAIT OVER THE WEEKEND. HAVE AMENDED ZONES EARLIER TO 
BACK OFF ON THE WINDS A BIT OVER THE AZ ZONES...AND WILL KEEP AN EYE 
ON THE WINDS OVER SERN CA TO SEE IF WIND ADVISORY NEEDS EXTENDING 
BEYOND 11 PM. OTHERWISE FORECASTS LOOK OK.  11

.PSR...WIND ADVISORY FOR SOUTHEAST CALIFORNIA ZONES 30...32...AND
       33...JOSHUA TREE NATIONAL PARK...RIVERSIDE COUNTY EASTERN
       DESERTS...AND IMPERIAL COUNTY UNTIL 11 PM PDT...0600 GMT
       THIS EVENING.