000 FXUS65 KPSR 091225 AAA AFDPSR AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PHOENIX AZ 525 AM MST MON NOV 9 2009 .UPDATE...UDPATED AVIATION AND FIRE WEATHER DISCUSSIONS && .SYNOPSIS... HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY AND TUESDAY...WITH NEAR RECORD HIGH TEMPERATURES TOMORROW IN PHOENIX. DRY WEATHER WILL CONTINUE INTO THE MIDDLE OF THE WEEK...AS WINDS GRADUALLY INCREASE AHEAD OF A PACIFIC STORM SYSTEM. A BIG CHANGE IS LIKELY BY FRIDAY AS A COLD FRONT SWEEPS ACROSS ARIZONA. BESIDES MUCH COOLER TEMPERATURES THERE WILL BE A SLIGHT CHANCE OF SHOWERS IN PHOENIX AND EASTWARD ON FRIDAY. MOSTLY SUNNY SKIES ARE FORECAST FOR NEXT SATURDAY AND SUNDAY. && .DISCUSSION... DRY WESTERLY FLOW ALOFT CONTINUES THIS MORNING ACROSS MUCH OF THE SOUTHWESTERN STATES. A SERIES OF WEAK IMPULSES WERE STREAMING INTO CALIFORNIA AND ARIZONA...BRINGING THIN HIGH CLOUDS FROM TIME TO TIME. MOISTURE WAS STILL VERY LIMITED OVER OUR AREA WITH SFC DEW POINTS IN THE 30S AND 40S. PREDAWN TEMPERATURES WERE RUNNING ABOUT THE SAME AS 24 HOURS AGO...WITH 50S AND 60S COMMON ON THE DESERTS. LATEST MODEL DATA INDICATED THE FAST WESTERLY FLOW ALOFT WILL SHIFT TO THE NORTH AS A STRONG UPPER RIDGE BUILDS OVER MEXICO THROUGH TUESDAY. GFS AND ECMWF BOTH SUGGEST STRONG WARMING ALOFT WHILE THE PACIFIC TROUGH GATHERS STRENGTH OFF THE WASHINGTON COAST. THE HIGH TEMPS WILL CLIMB INTO THE MID 80S ONCE AGAIN IN PHOENIX TODAY. BUT WITH SOMEWHAT STRONGER WINDS AND BETTER MIXING IN THE LOWER LEVELS TOMORROW...WE SHOULD SEE OUR WARMEST DAY OF THE WEEK. LATEST PHOENIX FORECAST NOW SHOWS THE 90 DEGREE HIGH WILL TIE THE RECORD SET BACK IN 1989. FOR VETERANS DAY AND THURSDAY...THE PAC TROUGH IS EXPECTED TO DIG SOUTHWARD AND ALLOW MORE MOISTURE...MAINLY AT THE HIGHER LEVELS...TO WORK EASTWARD TOWARD AZ. MODEL TRENDS SHOW THIS SYSTEM WILL BE A RATHER PROGRESSIVE ONE...WITH THE WINDS BECOMING THE MAIN CONCERN BY THURSDAY. STILL TOO EARLY TO SAY IF THE GRADIENT WILL TIGHTEN SUFFICIENTLY TO WARRANT A WIND ADVISORY ON THE DESERTS. BY FRIDAY...PRECIP WILL BE THE MAIN FORECAST CHALLENGE. AT THIS TIME WE LIKE THE GOOD MODEL AGREEMENT ON THE TIMING AND INTENSITY OF THE PAC TROUGH AND ASSOCIATED FRONT AS IT SWEEPS EASTWARD. WE WILL BUMP UP THE POPS TO SHOW A SLIGHT CHANCE OF SHOWERS IN PHOENIX AS EARLY AS THURSDAY NIGHT...AND LINGERING INTO FRIDAY. A FEW INSTABILITY SHOWERS LIKELY TO DEVELOP OVER ZONE 24...AND SHOULD LAST INTO SATURDAY. TEMPS LOOK TOO WARM FOR SNOW TO BE A FACTOR IN THE FORECASTS FOR THE HIGHER ELEVS OF SOUTHERN GILA COUNTY. && .AVIATION... KPHX...KIWA...KIPL...AND KBLH... LIGHT DIURNAL WINDS AND SOME MOSTLY THIN HIGH CLOUDINESS CONTINUING AT LEAST THROUGH TUESDAY MORNING. VFR CONDITIONS EXPECTED AT ALL AIRFIELDS NEXT 24 HOURS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... WEDNESDAY THROUGH SUNDAY... HIGH PRESSURE ALOFT WILL REMAIN STRONG WEDNESDAY WITH TEMPERATURES WELL ABOVE SEASONAL NORMALS. A SHARP CHANGE IN THE WEATHER IS THEN EXPEFTED TO OCCUR...AS A LOW PRESSURE SYSTEM FROM THE GULF OF ALASKA MOVES TOWARD ARIZONA THURSDAY. THIS SYSTEM WILL BRING MORE CLOUDS ...BREEZY WEATHER...AND SHARP DROP IN TEMPERATURES THURSDAY AND FRIDAY....WITH HIGH TEMPERATURES TO FALL BELOW SEASONAL NORMALS BY FRIDAY. HUMIDITY WILL INCREASE AND LEAD TO A SLIGHT CHANCE FOR SHOWERS THURSDAY NIGHT AND FRIDAY ACROSS SOUTH-CENTRAL ARIZONA... ESPECIALLY IN ZONE 133 SOUTHERN GILA COUNTY/TONTO NATIONAL FOREST FOOTHILLS. MUCH DRIER AIR WILL OVERSPREAD THE AREA DURING THE WEEKEND...MAINLY SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...WITH MINIMUM RH VALUES LOWERING BELOW 15 PERCENT MOST LOCATIONS WEST OF THE GREATER PHOENIX AREA. BREEZY NORTH WINDS ARE EXPECTED ALONG THE LOWER COLORADO RIVER VALLEY SATURDAY. A PARTIAL RECOVERY OF TEMPERATURES IS EXPECTED LATE IN THE WEEKEND AS THE LOW PRESSURE SYSTEM MOVES EAST OF OUR AREA. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...SIPPLE AVIATION...CB FIRE WEATHER...CB/ELLIS