000
FXUS65 KPSR 061135
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
435 AM MST TUE JAN 6 2009
.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.
&&
.SYNOPSIS...
LEFTOVER MOISTURE IS EXPECTED TO RESULT IN SOME PATCHY FOG MAINLY
EAST OF PHOENIX THIS MORNING. OTHERWISE ...HIGHER PRESSURE ALOFT
FROM THE PACIFIC WILL BRING DRY WEATHER TODAY THROUGH AT LEAST
THURSDAY WITH WARMER WEATHER IN SOUTHEAST CALIFORNIA AND FAR
SOUTHWEST ARIZONA TODAY...AND ACROSS THE ENTIRE AREA WEDNESDAY AND
THURSDAY. ANOTHER PASSING LOW PRESSURE SYSTEM IS EXPECTED TO BRING
TEMPERATURES BACK DOWN SOMEWHAT FRIDAY AND SATURDAY...BUT IT IS
EXPECTED TO REMAIN ON THE DRY SIDE...WITH ONLY A SLIGHT CHANCE FOR
SHOWERS EXPECTED SATURDAY OVER SOUTH-CENTRAL ARIZONA.
&&
.DISCUSSION...
AT 2 AM THIS MORNING...FAST MOVING SHORT WAVE ON THE BACK SIDE OF
THE DEPARTING UPPER TROF CONTINUES TO DROP QUICKLY SOUTH THRU FAR
EASTERN ARIZONA. OVERRUNNING AND FAVORABLE UPPER JET DYNAMICS
ALLOWED FOR SOME SHOWERS TO DEVELOP OVER ZONE 24 DURING THE LATE
EVENING AND EARLY MORNING HOURS...BUT 2 AM RADAR SHOWED THE SHOWERS
TO BE DECREASING AND MOVING OFF TO THE SOUTHEAST. BY SUNRISE OR
SO...EXPECT JUST PARTLY CLOUDY SKIES LEFT ACROSS ZONE 24...WITH
MOSTLY SUNNY SKIES TO DEVELOP ELSEWHERE AS SUBSIDENT NWLY FLOW
IMPACTS OUR CWA. THICKNESSES/HEIGHTS ARE FORECAST TO RISE ABOUT 60M
TODAY...BUT MOST OF THE WARMING WILL STAY ALOFT...SO EXPECT ANOTHER
COOL DAY OVER OUR DESERTS WITH HIGHS REMAINING WELL BELOW SEASONAL
NORMALS. PHOENIX SHOULD AGAIN STAY JUST BELOW 60 FOR A MAX TEMP.
PROGS CONTINUE TO AGREE THAT HIGH PRESSURE WILL BUILD IN ACROSS THE
DESERT SOUTHWEST TONIGHT THROUGH THURSDAY...LEADING TO MOSTLY CLEAR
SKIES AND A WARMING TREND. HIGHS SHOULD JUMP 4-6 DEGREES
WEDNESDAY...AND APPROACH CLIMATOLOGICAL NORMALS...WITH ANOTHER
HANDFUL DEGREES WARMING ON TAP FOR THURSDAY. IN FACT...MANY OF THE
WARMER DESERT LOCALES SHOULD REACH INTO THE LOW 70S THURSDAY.
FOR FRIDAY INTO THE WEEKEND...MODELS HAVE BEEN CONSISTENT OVER THE
PAST FEW DAYS IN ADVERTISING ANOTHER PACIFIC SHORTWAVE TO MOVE
SOUTHEAST AND ACROSS ARIZONA...BRINGING MAINLY COOLER TEMPERATURES
TO THE AREA. ALTHOUGH BOTH THE ECMWF AND GFS ADVERTISE THIS
SYSTEM...ECMWF HAS BEEN THE MORE PROGRESSIVE OF THE TWO MODELS. BY
SATURDAY EVENING...ECMWF HAS AN OPEN WAVE SYSTEM WITH THE TROF AXIS
PUSHING SOUTHEAST OF OUR CWA. MEANWHILE THE GFS CLOSES OFF AN UPPER
LOW OVER CENTRAL AZ. FOR THE PAST SEVERAL MODEL RUNS GFS HAS CALLED
FOR A CLOSED LOW TO DEVELOP AS THE TROF DROPS SOUTH THRU
ARIZONA...BUT IT HAS BEEN ALL OVER THE MAP WITH THE EXACT LOCATION
AND DEPTH OF THE UPPER LOW. GFS TENDS TO REALLY GEN UP IMPRESSIVE
CLOSED LOWS IN THE LATTER PORTIONS OF THE EXTENDED PERIOD BUT QUITE
OFTEN THESE FEATURES ARE WAY OVERDONE...OR SIMPLY FIGMENTS OF THE
MODELS IMAGINATION. BASED ON TRACK RECORDS OF THE EUROPEAN...WILL
FAVOR ITS SOLUTION OVER THE GFS. IT DOES LOOK LIKE THIS SYSTEM WILL
BE ON THE DRY SIDE FOR US...BUT WE WILL CONTINUE TO FORECAST CLIMO
POPS FRIDAY NIGHT INTO SATURDAY NIGHT...WITH THE BEST THREAT FOR
PRECIP LIKELY TO BE SATURDAY OVER SOUTH-CENTRAL ARIZONA. SATURDAY
ALSO LOOKS TO BE THE COOLEST DAY OF THE EXTENDED...WITH HIGH TEMPS
TO DROP BACK BELOW SEASONAL NORMALS.
ON MONDAY...UPPER RIDGE FORECAST TO BE JUST OFF WEST COAST...PUTTING
AZ UNDER DRY NWLY FLOW ALOFT. EXPECT MOSTLY SUNNY SKIES ALONG WITH A
MODEST AMOUNT OF WARMING.
&&
.AVIATION...
ALL TAF SITES...EXPECT LIGHT WIND...GENERALLY LESS THAN 6 KTS...WITH
MOSTLY SUNNY SKIES. CLOUDS WILL REMAIN AOA 25K FT. LIGHT DRAINAGE
WINDS OVERNIGHT.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
THURSDAY THROUGH MONDAY...DRIER CONDITIONS AND A GRADUAL WARMING
TREND WILL CONTINUE REGION WIDE AS HIGH PRESSURE BUILDS OVER THE
AREA. WINDS WILL BE LIGHT AND DAYTIME HUMIDITY LEVELS WILL TREND
DOWN...DROPPING INTO THE LOW 20S BY THE END OF THE WEEKEND. BY
FRIDAY AFTERNOON THROUGH THE WEEKEND...WINDS INCREASE AND BECOME
GUSTY...INTO THE 10 TO 20 MPH RANGE...MAINLY ALONG PORTIONS OF THE
LOWER COLORADO RIVER VALLEY AND HIGHER TERRAIN. LIGHT WIND IS
ANTICIPATED FOR MONDAY.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...CB
AVIATION...PADDOCK
FIRE WEATHER...PADDOCK
