Weather Service Report


671 
FXUS65 KPSR 270353
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
855 PM MST WED NOV 26 2014

.SYNOPSIS...
DRY AIR WILL CONTINUE TO OVERSPREAD THE AREA RESULTING IN CLEAR TO 
MOSTLY CLEAR SKIES INTO THE WEEKEND. AFTERNOON TEMPERATURES WILL 
PEAK IN THE UPPER 70S/LOWER 80S TOWARD THE END OF THE WEEK AS A 
STRENGTHENING HIGH PRESSURE RIDGE POSITIONS ITSELF OVER THE DESERT 
SOUTHWEST. A LOW PRESSURE SYSTEM EXPECTED FOR EARLY OR MID NEXT WEEK 
WILL BRING CHANCES FOR RAIN AND MUCH COOLER TEMPERATURES.

&&

.DISCUSSION...
A RATHER QUIET...AND PLEASANT DAY TODAY ACROSS OUR CWA...ESPECIALLY 
COMPARED TO THE CENTRAL AND EASTERN PARTS OF THE NATION. HIGH 
PRESSURE THAT IS NOW BUILDING EASTWARD OVER THE DESERT SOUTHWEST 
ALLOWED TEMPERATURES TO WARM ACROSS THE REGION...WITH PHOENIX SKY 
HARBOR REACHING A HIGH OF 74...3 DEGREES ABOVE THE AVERAGE FOR THIS 
DATE OF 71. THE ONLY ISSUE THIS EVENING IS THE PRESENCE OF SMOKE IN 
SOME AREAS FROM A MULCH FIRE NEAR LUKE AFB. A RATHER STABLE 
AIRMASS WILL LIKELY ALLOW THE SMOKE TO BUILD UP A BIT MORE TONIGHT 
AND EARLY THURSDAY BEFORE MIXING OUT SOMEWHAT LATER ON 
THURSDAY...WITH THE HIGHEST SMOKE CONCENTRATIONS LIKELY TO BE OVER 
THE WESTERN PORTIONS OF THE GREATER PHOENIX AREA. WIDESPREAD HIGHS 
IN THE LOW 80S STILL LOOK LIKE A GOOD BET ON THURSDAY AS A 
COMBINATION OF A LITTLE MORE WARMING IN THE MID-LEVELS OF THE 
ATMOSPHERE (1-2 DEGREES C) AND LIGHT DOWNSLOPE NE-LY WINDS HELP TO 
WARM TEMPS FURTHER NEAR THE SURFACE. AS FAR AS THE SHORT-TERM IS 
CONCERNED...OTHER THAN ADDING SOME LOCAL SMOKE TO THE GRIDDED 
FORECASTS...CURRENT INHERITED FORECASTS LOOK GOOD...AND NO UPDATES 
ARE PLANNED.

&&

.PREVIOUS DISCUSSION...
12Z RAOB SOUNDINGS FROM AROUND THE AREA ALL SHOW CONTINUED WARMING 
THROUGHOUT THE COLUMN. FROM SAN DIEGO TO TUCSON...A 10 DEGREE 
WARMING IN THE 600-700MB LAYER THE PREVIOUS DAY HAS TRANSLATED A BIT 
LOWER NEAR THE SURFACE THIS MORNING. THIS LINES UP WELL WITH THE 
STRENGTHENING RIDGE OF HIGH PRESSURE SETTLING OVER THE SOUTHWEST. 
TEMPERATURES SHOULD PEAK ON THURSDAY IN THE LOW 80S FOR MOST 
LOCATIONS IN THE LOWER DESERTS BEFORE A WEAK SHORTWAVE TROUGH SWEEPS 
BY TO OUR NORTH ON FRIDAY TO BEGIN BREAKING DOWN OUR 
RIDGE...CREATING A GRADUAL COOLING TREND BACK TO SEASONAL NORMALS BY 
EARLY NEXT WEEK. 

THE SHORTWAVE FEATURE THAT WILL SWEEP BY ON FRIDAY WILL START THE 
PROCESS OF BREAKING DOWN THE RIDGE OF HIGH PRESSURE AND MAKE WAY FOR 
A LARGER PACIFIC LOW PRESSURE SYSTEM SWINGING DOWN FROM ALASKA. BY 
MONDAY...FORECAST MODELS HAVE THE LOW POSITIONED OFF THE NORTHERN 
CALIFORNIA COAST. MODEL DIFFERENCES EXIST IN TIMING OF THE SYSTEM TO 
MOVE INTO CALIFORNIA AND LOCATION FOR HOW FAR SOUTH IT WILL SWING. 
THE GFS HAS SLOWED THE SYSTEM TIMING DOWN QUITE A BIT IN THE LAST 
4-5 MODEL RUNS...HOWEVER THE GENERAL TRACK LOCATION HAS NOT VEERED 
MUCH. ELONGATED SOUTHWARD...THE SYSTEM WILL TAP INTO SOME 
SUB-TROPICAL MOISTURE INCREASING PWAT VALUES TO AROUND 1 INCH FOR 
FAR SOUTHWEST ARIZONA BY NEXT TUESDAY. ENSEMBLE MEMBER MODELS SHOW A 
DECENT CHANCE (20-30 PERCENT) FOR MEASURABLE RAIN ACROSS SOUTHERN 
CALIFORNIA AND NEARLY 60 PERCENT OF ARIZONA. AGAIN...TIMING WILL BE 
TRICKY JUST YET AND RAINFALL AMOUNTS ARE UP IN THE AIR AT THIS 
POINT. MOST OF THE DETERMINISTIC FORECAST MODELS PAINT A CHANCE FOR 
PRECIPITATION BY LATE TUESDAY AND INTO WEDNESDAY. LATEST MODEL RUNS 
HAVE AGAIN SLOWED DOWN IN TIMING...AND I WOULD NOT BE SURPRISED IF 
THEY CONTINUE TO DO SO AS WE GET CLOSER TO THE EVENT. BOTTOM LINE IS 
A CONSIDERABLE AMOUNT OF MOISTURE INCREASE AHEAD OF A COLD PACIFIC 
SYSTEM SHOULD BRING RAIN TO ARIZONA BY NEXT WEEK.     

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...AND 
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...INCLUDING KIPL AND 
KBLH...

LIGHT WINDS FAVORING NORTHWEST THROUGH NORTHEAST DIRECTIONS CAN BE 
EXPECTED THROUGH TONIGHT WITH EAST AND NORTHEAST DIRECTIONS FAVORED 
DURING THE DAY THURSDAY. AREAS OF REDUCED VISIBILITIES CAN BE 
EXPECTED OVER WESTERN PORTIONS OF THE PHOENIX METRO DUE TO SMOKE 
FROM A MULCH FIRE NEAR LUKE AFB. ANTICIPATE SOME LOCAL BREEZINESS 
NEAR FOOTHILL LOCATIONS TONIGHT...EXPANDING TO THE VALLEY FLOORS 
DURING THE DAY THURSDAY. EXPECT CLEAR SKIES EXCEPT FOR SOME VERY 
MINOR CIRRUS. 

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
HIGH PRESSURE WILL REMAIN IN CONTROL THROUGH SUNDAY...RESULTING IN A 
CONTINUED PERIOD OF MOSTLY CLEAR SKIES AND DRY CONDITIONS. SINGLE 
DIGIT HUMIDITIES WITH FAIR OVERNIGHT RECOVERIES WILL BE COMMON 
THROUGH THE WEEKEND. LOOKING AHEAD...A LARGE UPPER TROUGH WILL MOVE 
THROUGH CALIFORNIA AND INTO THE DESERT SOUTHWEST EARLY NEXT WEEK 
BRINGING A PERIOD OF UNSETTLED WEATHER TO THE REGION. STILL NEED TO 
WORK OUT THE TIMING DETAILS BUT AT THIS POINT MOST NUMERICAL 
GUIDANCE SUGGESTS RAIN MOVING INTO THE AREA ON TUESDAY ALONG WITH 
ELEVATED HUMIDITIES AND COOLER TEMPERATURES. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA/DEWEY
AVIATION...AJ
FIRE WEATHER...LEINS



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