000 FXUS65 KPSR 201723 AFDPSR AZZ020>028-CAZ030>033-202245- SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 1020 AM MST WED MAR 20 2002 .SYNOPSIS... MUCH WARMER WEATHER WITH CLEAR NIGHTS AND SUNNY DAYS ARE FORECAST THROUGH FRIDAY...AS STRONG HIGH PRESSURE BUILDS OVER THE REGION. UNSEASONABLY WARM TEMPERATURES ARE EXPECTED BY THURSDAY...WHEN DAYTIME HIGHS WILL BE NEAR 90 DEGREES OVER MANY LOWER DESERT LOCATIONS. HIGH PRESSURE IS FORECAST TO BREAK DOWN THIS WEEKEND AS A SERIES OF PACIFIC WEATHER SYSTEMS MOVE INTO THE WESTERN STATES...INCLUDING ARIZONA. DRY...COOLER AND BREEZY WEATHER IS EXPECTED THIS WEEKEND WITH BELOW NORMAL TEMPERATURES SUNDAY AND MONDAY. .DISCUSSION... WARMING TREND OCCURRING AS ADVERTISED. CLEAR SKIES ATTM...AND THAT WONT CHANGE AS UPPER RIDGE BUILDS OVER FAR SOUTHEAST CALIFORNIA AND SOUTHWEST AZ. 24 HR 500 MB HEIGHTS UP 110 M AT YUMA AND 210 M AT TUCSON...WITH 12 HR 500 MB CHANGE +50-60 M. NCEP 500 MB ENSEMBLE MEAN FORECAST FOR 00Z THURSDAY INDICATES 500 MB HEIGHTS TO RISE 40-50 M TODAY TO NEAR 5800 M...ABOUT 100 M ABOVE CLIMO. NOT SURPRISINGLY...YUMA SOUNDING WAS WARMER BY 3-6 C IN 850-950 MB LAYER COMPARED TO YESTERDAY. 850 MB TEMPS EXPECTED TO RISE TO ABOVE 16 C BY THIS EVENING OVER SOUTH CENTRAL AZ...WITH SOMEWHAT LESSER WARMING EXPECTED OVER FAR SOUTHEAST CALIFORNIA AND FAR SOUTHWEST AZ. AS OF 10 AM MST...24 HR DELTA TEMP OVER SOUTH CENTRAL AZ WAS UP BY 7-9 F ...WHILE DEW POINTS WERE DOWN 5-10 F. TEMP/DEW POINT TRENDS SUPPORTED TO SOME DEGREE BY A SLIGHT DOWNSLOPING 10-20 MPH EAST- SOUTHEAST WIND IN 3-8 KFT LAYER. MOST DESERT LOCATIONS TOPPED OUT IN THE MID 70S YESTERDAY...AND WITH A 10 DEGREE WARMUP POSSIBLE TODAY DAYTIME HIGHS WILL BE IN THE MID 80S AT MOST DESERT LOCATIONS...AND HIGHS MAY BE A DEGREE OR TWO WARMER THAN CURRENT FORECAST INDICATES. EVEN WARMER TEMPS EXPECTED THURSDAY...WITH HIGHS NEAR OR SLIGHTLY ABOVE 90 EXPECTED AT MANY LOWER ELEVATION DESERT LOCALES. CERTAINLY THIS WILL BE UNSEASONABLE WARMTH FOR MUCH OF THE FORECAST AREA...AS THE AVERAGE HIGH FOR THURSDAY AT PHOENIX IS 77 F. COULD GET CLOSE TO RECORD HIGHS OVER SOUTH-CENTRAL AZ THURSDAY...AS THURSDAY RECORD HIGH TEMP IS 92 AT PHOENIX. NO UPDATE PLANNED...BUT MAY DECIDE TO NUDGE MAX TEMPS UP A BIT MAINLY OVER S-CNTRL AZ FOR TODAY IF CURRENT TRENDS CONTINUE. DG .PSR...NONE.