FXUS65 KPSR 011758
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1055 AM MST TUE DEC 1 2009
.SYNOPSIS...
A FLOW ALOFT IS FROM THE NORTHWEST IS EXPECTED TO RESULT IN DRY
WEATHER WITH TYPICAL TEMPERATURES FOR EARLY DECEMBER AT LEAST THROUGH
THURSDAY. AFTER SUNNY SKIES TODAY...HIGH CLOUDINESS IS EXPECTED
TONIGHT AND WEDNESDAY...FOLLOWED BY SUNNY SKIES THURSDAY. A DRY COLD
FRONT FROM THE NORTH IS EXPECTED TO BRING BREEZY WEATHER TO SOUTHEAST
CALIFORNIA AND SOUTHWEST ARIZONA THURSDAY AND SOUTH-CENTRAL ARIZONA
BY FRIDAY ALONG WITH VERY DRY AND SOMEWHAT COOLER AIR. HIGH
CLOUDINESS IS EXPECTED TO INCREASE BY FRIDAY NIGHT AND SATURDAY
FOLLOWED BY UNSETTLED WEATHER EARLY NEXT WEEK AS A PACIFIC STORM
SYSTEM MOVES INTO OUR AREA.
&&
.DISCUSSION...
UNDER SUNNY SKIES...TEMPERATURES WERE GENERALLY 2 TO 6 DEGREES COOLER
AND DEW POINT TEMPERATURES GENERALLY 3 TO 5 DEGREES LOWER LATE THIS
MOONING COMPARED WITH THE SAME TIME YESTERDAY. HOWEVER...IT WAS
SOMEWHAT WARMER IN THE HIGHER TERRAIN INCLUDING SOUTHERN GILA COUNTY
AND JOSHUA TREE NATIONAL PARK. WIND WAS GENERALLY CALM OR LIGHT
MOSTLY DOWNSLOPE/DOWNVALLEY THIS MORNING.
A WEAK AXIS OR RIDGE OF HIGH PRESSURE IN A FLOW ALOFT FROM THE
NORTHWEST WILL MOVE SOUTHEAST OVER OUR AREA TODAY. THIS MEANS SUNNY
SKIES TODAY. DESPITE THE HIGHER PRESSURE ALOFT...TEMPERATURES ARE
EXPECTED TO BE SLIGHTLY LOWER TODAY AS THE INVERSION OF RELATIVELY
COOLER AIR NEAR THE SURFACE OF THE VALLEYS AND WARMER AIR ALOFT AND
AT HIGHER ELEVATIONS HAS BECOME STRONGER WHICH IS TYPICAL FOR THIS
TIME OF YEAR.
EXCEPT FOR HIGH CLOUDINESS BY LATE TUESDAY NIGHT INTO WEDNESDAY...A
FLOW ALOFT FROM THE NORTHWEST IS EXPECTED TO BE DRY WITH MOSTLY
CLEAR NIGHTS AND SUNNY DAYS THROUGH THURSDAY AND INTO FRIDAY.
TYPICAL TEMPERATURES FOR THIS TIME OF YEAR ARE ALSO EXPECTED.
THE DRY FAR SOUTHWEST END OF LARGE LOW PRESSURE SYSTEM ALOFT
CENTERED OVER THE UPPER MIDWEST WILL MOVE SOUTHEAST ACROSS OUR AREA
LATE THURSDAY AND THURSDAY NIGHT. STRONG SURFACE HIGH PRESSURE
BEHIND THIS SYSTEM IS EXPECTED TO BUILD OVER NEVADA AND UTAH WITH
BREEZY WINDS FROM THE NORTH IN SOUTHEAST CALIFORNIA AND SOUTHWEST
ARIZONA THURSDAY INTO FRIDAY...ESPECIALLY DOWN THE LOWER COLORADO
RIVER VALLEY. ALSO...AN INCREASE IN BREEZINESS FROM THE NORTHEAST IS
EXPECTED IN SOUTH-CENTRAL ARIZONA BY FRIDAY MORNING AND EARLY
AFTERNOON. THESE WINDS WILL BRING SOMEWHAT COOLER AND VERY DRY AIR
INTO OUR AREA WITH SINGLE DIGIT MINIMUM AFTERNOON RELATIVE HUMIDITY
FRIDAY.
A WEAK PACIFIC LOW PRESSURE SYSTEM FROM THE WEST IS EXPECTED TO
SPREAD CONSIDERABLE HIGH CLOUDINESS OVER OUR AREA FRIDAY NIGHT AND
SATURDAY.
A HIGH PRESSURE SYSTEM ALOFT IS EXPECTED TO BECOME ANCHORED IN THE
GULF OF ALASKA AND ALASKA THIS COMING WEEKEND AND EARLY NEXT WEEK.
AT THE SAME TIME...A STRONG AND COLD LOW PRESSURE SYSTEM IS EXPECTED
TO DEVELOP NEAR THE PACIFIC NORTHWEST COAST INTO MONDAY. SUBTROPICAL
MOISTURE IS EXPECTED TO MOVE INTO OUR AREA AS THE SUBTROPICAL JET
STREAM FROM THE WEST MOVES IN WELL SOUTH OF THE LOW PRESSURE CENTER.
THIS IS EXPECTED TO RESULT IN UNSETTLED WEATHER FOR OUR AREA EARLY
NEXT WEEK. AS IS TYPICAL THAT FAR OUT IN TIME...THE TRACK AND TIMING
IS SOMEWHAT UNCERTAIN...BUT IT DOES LOOK AS IF OUR WEATHER WILL
BECOME UNSETTLED. WILL BE LOOKING AT THIS FOR THE AFTERNOON FORECAST
PACKAGE AS WE WILL PROBABLY HAVE TO INCREASE THE CHANCE OF RAIN
EARLY NEXT WEEK. THIS SYSTEM HAS THE POTENTIAL TO PRODUCE SIGNIFICANT
RAIN IN OUR AREA EARLY NEXT WEEK...BUT THERE IS STILL MUCH
UNCERTAINTY THIS FAR OUT IN TIME. STAY TUNED.
&&
AVIATION...
SOUTH CENTRAL AZ...INCLUDING KPHX AND KIWA...
HIGH PRESSURE ALOFT CENTERED WEST OF ARIZONA WILL KEEP DRY NORTHWEST
FLOW ALOFT IN PLACE OVER SOUTH-CENTRAL ARIZONA TODAY. WINDS WILL BE
MOSTLY LIGHT DIURNAL...WITH NORMAL DRAINAGE WIND PATTERN FOR KPHX.
SOME INCREASE IN HIGH CIRRUS EXPECTED THIS AFTERNOON...WITH THIN
BROKEN AOA 20K FEET AFTER 18Z...OTHERWISE DRY LOW LEVELS. NO
AVIATION CONCERNS NEXT 24 HOURS.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...CLEAR
SKIES THIS MORNING...WITH INCREASING HIGH THIN CIRRUS AFTER 18Z.
SOME MAINLY THIN BKN CIGS AOA 20K FEET BY AFTERNOON. WINDS WILL BE
RATHER LIGHT AND VARIABLE NEXT 24 HOURS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
HIGH PRESSURE ALOFT CENTERED NEAR THE WEST COAST WILL DOMINATE OUR
WEATHER PATTERN THURSDAY THROUGH SATURDAY...GIVING MOSTLY CLEAR
SKIES AND DRY CONDITIONS. A WEATHER SYSTEM MOVING SOUTH THROUGH THE
ROCKIES WILL USHER IN MUCH DRIER LOW LEVEL AIR FRIDAY AND
SATURDAY...WITH MINIMUM RH VALUES FALLING INTO THE SINGLE DIGITS
OVER MUCH OF THE LOWER DESERT. INCREASED WIND CAN BE EXPECTED FRIDAY
WITH THIS SYSTEM...ESPECIALLY ALONG THE LOWER COLORADO RIVER VALLEY
WHERE NORTH WINDS WILL GUST BETWEEN 20 AND 30 MPH AT TIMES. HIGH
TEMPERATURES WILL NOT CHANGE MUCH DURING THE PERIOD...REMAINING NEAR
OR A BIT BELOW SEASONAL NORMALS.
HIGH PRESSURE WILL BREAK DOWN SUNDAY INTO EARLY NEXT WEEK AS LOW
PRESSURE DEVELOPS ALONG THE WEST COAST. THIS WILL LEAD TO INCREASING
CLOUDS...A SLIGHT CHANCE FOR SHOWERS AND HIGHER HUMIDITY. SOME
INCREASE IN WIND ALONG WITH COOLER TEMPERATURES WILL ACCOMPANY THIS
CHANGING WEATHER PATTERN.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...ELLIS
AVIATION...CB
FIRE WEATHER...CB
