FXUS65 KPSR 021731
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1030 AM MST WED DEC 2 2009
.SYNOPSIS...
A FLOW ALOFT FROM THE NORTHWEST WILL RESULT IN DRY WEATHER WITH
TYPICAL TEMPERATURES FOR EARLY DECEMBER AT LEAST THROUGH THURSDAY.
SOME MAINLY HIGH CLOUDINESS IS EXPECTED TODAY FOLLOWED BY CLEAR SKIES
TONIGHT AND THURSDAY. A DRY COLD FRONT FROM THE NORTH WILL BRING
BREEZY WEATHER TO SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA THURSDAY
AND SOUTH-CENTRAL ARIZONA BY FRIDAY ALONG WITH COOLER AND VERY DRY
AIR. HIGH CLOUDINESS IS EXPECTED TO INCREASE BY FRIDAY NIGHT AND
SATURDAY FOLLOWED BY UNSETTLED WEATHER AND A CHANCE OF RAIN EARLY
NEXT WEEK AS A PACIFIC STORM SYSTEM MOVES INTO OUR AREA.
&&
.DISCUSSION...
SOME HIGH CLOUDINESS FROM THE NORTHWEST WAS MOVING SOUTHEAST ACROSS
THE AREA WITH PARTLY TO MOSTLY SUNNY SKIES THIS MORNING. THERE WAS
ALSO SOME LOW CLOUDS DUE TO MOISTURE FROM THE GULF OF CALIFORNIA IN
FAR SOUTHWEST ARIZONA INCLUDING THE YUMA AREA. TEMPERATURES WERE
GENERALLY A DEGREE OR TWO COOLER LATE THIS MORNING COMPARED WITH THE
SAME TIME YESTERDAY. DEW POINT TEMPERATURES WERE GENERALLY 2 OR 3
DEGREES LOWER IN SOUTH-CENTRAL ARIZONA INCLUDING THE GREATER PHOENIX
AREA AND 8 TO 20 DEGREES HIGHER IN FAR SOUTHWEST ARIZONA AND
SOUTHEAST CALIFORNIA. WINDS WERE GENERALLY CALM OR LIGHT DOWNSLOPE/
DOWNVALLEY THIS MORNING.
THE HIGH CLOUDS HAVE NOT BEEN AS THICK AS EXPECTED THIS MORNING...
BUT HIGH CLOUDS COULD BE JUST THICK ENOUGH TO CUT DOWN ON SOME OF
THE SUNSHINE TODAY. ALSO...AS MENTIONED EARLIER THERE HAVE BEEN LOW
CLOUDS IN FAR SOUTHWEST ARIZONA INCLUDING THE YUMA AREA. THUS...
PLANNING ON LEAVING THE FORECAST OF PARTLY SUNNY TODAY...AND
NO OTHER IMMEDIATE UPDATES ARE PLANNED THIS MORNING.
PREVIOUS DISCUSSION...
IN A NUTSHELL...FORECAST LOOKS DRY THROUGH THE SHORT TERM...BUT BY
LATE IN THE WEEKEND AND INTO EARLY NEXT WEEK...A MAJOR CHANGE IN THE
WEATHER PATTERN IS EXPECTED WITH MUCH WETTER CONDITIONS DEVELOPING.
FOR TODAY...HIGH AMPLITUDE UPPER RIDGE JUST OFF THE WEST COAST WILL
GIVE A DRY NORTHERLY FLOW ALOFT TO THE AREA...WITH SOME HIGH CLOUDS
EMBEDDED IN THE FLOW AS SEEN IN THE 2 AM IR IMAGERY. TEMPS SHOULD
HOVER NEAR SEASONAL NORMALS UNDER PARTLY TO MOSTLY SUNNY SKIES.
SURFACE DEWPOINTS EARLY THIS MORNING ACROSS THE DESERTS RANGED FROM
THE LOW 20S TO MID 30S FOR THE MOST PART...BUT MUCH DRIER AIR IS
EXPECTED TO STREAM IN FROM THE NORTH BY FRIDAY.
PROGS AGREE THAT A WEATHER DISTURBANCE MOVING SOUTH AND THROUGH THE
ROCKIES THURSDAY THROUGH FRIDAY WILL BRING A COLD FRONT THROUGH THE
AREA...DROPPING MAX TEMPS 5-7 DEGREES ACROSS THE REGION...AND INTO
THE LOW TO MID 60S FRIDAY OVER THE LOWER DESERT. EXPECT PHOENIX TO
FALL FROM 67 THURSDAY TO 62 FRIDAY. IN ADDITION TO THE COOLER
TEMPS...VERY DRY AIR WILL ALSO SPREAD ACROSS THE AREA FROM THE
NORTH. BY FRIDAY AFTERNOON MOST OF THE CWA WILL SEE SINGLE DIGIT OR
EVEN NEGATIVE SURFACE DEWPOINTS...WITH THIS DRY AIR EXPECTED TO
LINGER INTO SATURDAY. NORTH WINDS THURSDAY NIGHT INTO FRIDAY WILL
BECOME BREEZY OR LOCALLY WINDY...OUT WEST...ESPECIALLY DOWN THE
LOWER CO RIVER VALLEY. ALSO...BREEZY NORTHEAST WINDS ARE ON TAP FOR
SOUTH-CENTRAL AZ BY FRIDAY.
OVER THE WEEKEND...BOTH THE GFS AND EUROPEAN CARVE OUT A SUBSTANTIAL
LOW PRESSURE TROF OVER THE WESTERN CONUS...CENTERED OVER THE PAC
NORTHWEST. INCREASING WESTERLY FLOW ALOFT OVER ARIZONA WILL START TO
SPREAD MID/HI CLOUDINESS INTO ARIZONA AS A SUBTROPICAL MOISTURE TAP
DEVELOPS. WITH THE LOW LEVELS STARTING OUT SO VERY DRY...IT WILL
TAKE TIME TO WET UP THE ATMOSPHERE...AND AS SUCH WE WILL ONLY
INTRODUCE CLIMO POPS ACROSS THE CWA SUNDAY...AND CALL FOR PARTLY
CLOUDY SKIES. THICKNESS VALUES REALLY DO NOT CHANGE MUCH FROM MID
WEEK...AND AS SUCH MAX TEMPS WILL REMAIN NEARLY FLAT LINED...IN THE
MID 60S TO LOW 70S...BOTH DAYS.
BY FAR THE MOST INTERESTING WEATHER IS SET TO COME EARLY NEXT
WEEK...ESPECIALLY IF THE GFS IS A PERFECT PROG. GFS AND ECMWF START
TO DIVERGE BY DAY 6...AS IS MOST OFTEN THE CASE...BUT WE MAY TEND TO
FAVOR THE GFS AS IT HAS SHOWN REMARKABLE RUN TO RUN CONSISTENCY OVER
THE PAST 4 OR 5 RUNS...AND ENSEMBLE MEMBERS AND ENSEMBLE MEAN
SUPPORT OPERATIONAL RUNS. GFS IS MORE AGGRESSIVE IN BRINGING MOST OF
THE ENERGY OVER THE PAC NW SOUTHEASTWARD AND ACROSS ARIZONA MONDAY
INTO TUESDAY. GIVEN THE IMPRESSIVE MOISTURE TAP ADVERTISED AND
BEAUCOUP UVVS FORECAST FOR MONDAY NIGHT...A PERFECT PROG GFS WOULD
SUGGEST CATEGORICAL POPS OVER MUCH OF SOUTH-CENTRAL AZ. OF
COURSE...THIS IS ALL AT THE DAY 6-7 TIME FRAME AND DESPITE
CONFIDENCE IN A WEATHER EVENT RUNNING HIGH...WOULD NOT DREAM OF
GOING THAT HIGH WITH OUR POPS AT THIS TIME. HAVE RAISED OUR POP
NUMBERS MONDAY THROUGH TUESDAY...AND MOST LOCALES WILL CARRY 20-30
PERCENT THROUGH THIS PERIOD. STAY TUNED...THINGS COULD GET WET AND
INTERESTING AROUND HERE EARLY NEXT WEEK.
&&
AVIATION...
SOUTHEAST CALIFORNIA...SOUTHWEST AND SOUTH-CENTRAL AZ...INCLUDING
KPHX...KIWA...KIPL...AND KBLH.
CLEAR OR THIN CIFM CLOUDS. WINDS LIGHT THRU 12Z THURSDAY. KPHX
WILL SEE A TYPICAL LGT WEST BREEZE DEVELOPING AFT 21Z.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
A LOW PRESSURE SYSTEM WILL MOVE THROUGH THE SOUTHERN ROCKIES BY
FRIDAY. THE ASSOCIATED COLD FRONT WILL BRING AN INCREASE IN THE WIND
LATE THURSDAY...AND INTO FRIDAY. MUCH DRIER AIR WILL SPREAD ACROSS
ALL ZONES ON FRIDAY...WITH MINIMUM RH VALUES DROPPING INTO THE
SINGLE DIGITS THROUGHOUT THE DESERTS. AT THIS TIME...CRITICAL FIRE
WEATHER THRESHOLDS ARE NOT EXPECTED TO BE REACHED.
INCREASING CLOUDS AND HUMIDITY ARE EXPECTED LATE IN THE WEEKEND...AS
A MAJOR CHANGE IN THE PATTERN DEVELOPS. A SERIES OF PACIFIC STORMS
ARE EXPECTED TO MOVE ACROSS THE REGION...FOR AN INCREASING CHANCE
OF SHOWERS PARTICULARLY MONDAY AND TUESDAY.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...ELLIS/CB
AVIATION...SIPPLE
FIRE WEATHER...SIPPLE
