Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 311606
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
905 AM MST FRI OCT 31 2014

.SYNOPSIS...
ANOTHER DAY OF WELL ABOVE NORMAL TEMPERATURES IS EXPECTED TODAY
UNDER MOSTLY SUNNY SKIES. SIGNIFICANTLY COOLER READINGS ARE THEN
EXPECTED FOR THE WEEKEND... AS A LOW PRESSURE SYSTEM AND COLD FRONT
PUSH THROUGH THE DESERT SOUTHWEST. HIGHS IN THE LOWER DESERTS WILL
DROP INTO THE UPPER 70S OR LOW 80S ON SATURDAY AND FALL TO THE LOWER
70S ON SUNDAY. IN ADDITION TO THE COOLER TEMPERATURES...PERIODS OF
BREEZY CONDITIONS CAN BE EXPECTED THROUGHOUT THE WEEKEND. RAIN
CHANCES WILL BE SLIGHT AND CONFINED MOSTLY TO THE HIGHER TERRAIN
EAST OF PHOENIX. A GRADUAL WARMING TREND WILL BEGIN MONDAY INTO THE
MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
FORECAST AREA IS SITUATED BETWEEN AN UPPER LEVEL RIDGE TO THE EAST
AND A TROUGH OFF THE WEST COAST. VEERING PROFILE IS ALSO EVIDENT
WITH EAST WINDS IN THE LOWER LEVELS AND A STRONGER SOUTHERLY FLOW AT
700 MB. LATEST HI-RES GUIDANCE INDICATES THAT BREEZY DOWNSLOPE
WINDS WILL DEVELOP THIS MORNING ACROSS THE FOOTHILLS OF THE
SUPERSTITION MOUNTAINS. GUSTS AS HIGH AS 25 MPH WILL BE POSSIBLE
ACROSS EASTERN PINAL COUNTY...THOUGH THIS TRAJECTORY IS NOT
FAVORABLE FOR BLOWING DUST. OTHERWISE...WELL-ABOVE AVERAGE
TEMPERATURES ARE EXPECTED TODAY WITH LOWER DESERT HIGHS IN THE LOWER
90S. HOWEVER...RECORD HIGH OF 96 DEGREES IN PHOENIX AND 98 DEGREES
IN YUMA APPEAR OUT OF REACH. LATEST HRRR SUGGESTS THE POSSIBILITY OF
ISOLATED CONVECTION DEVELOPING THIS AFTERNOON...THOUGH CONSENSUS
AMONG THE HI-RES AND GLOBAL GUIDANCE IS THAT THIS WILL BE WELL TO
OUR EAST...CLOSER TO THE WHITE MOUNTAINS. FORECAST IS IN GOOD SHAPE
AND ONLY MINOR SHORT-TERM ADJUSTMENTS WERE MADE TO THE HOURLY
TEMPERATURES.

&&

.PREVIOUS DISCUSSION...
MODEL GUIDANCE...INCLUDING GFS ENSEMBLE MEMBERS...REMAIN CONSISTENT
IN CALLING FOR THE DEEP AND COLD TROF TO PUSH ACROSS ARIZONA THIS
WEEKEND...BRINGING MUCH COOLER TEMPS...A SLIGHT CHANCE FOR SHOWERS
ACROSS SOUTH CENTRAL AZ...AND BREEZY/LOCALLY WINDY WEATHER ON
SATURDAY. THE TROF WILL MOVE THROUGH AS A SERIES OF WAVES...WITH THE
FIRST WAVE QUICKLY RACING NORTHEASTWARD AND ACROSS THE STATE
SATURDAY. THE FIRST COLD FRONT SATURDAY WILL LEAD TO ABOUT 10
DEGREES OF COOLING TO GO ALONG WITH BREEZY OR LOCALLY WINDY
SOUTHWEST WINDS. MOISTURE AND DYNAMICS WILL BE SOMEWHAT LIMITED SO
PRECIP WILL BE CONFINED TO AREAS MAINLY NORTH AND EAST OF
PHOENIX...ACROSS THE HIGHER TERRAIN...AND POPS WILL STAY MOSTLY
BELOW 15 PERCENT. THE SECOND...AND STRONGER...WAVE MOVES ACROSS THE
STATE SUNDAY INTO SUNDAY NIGHT...AND THE GFS ACTUALLY DEVELOPS A
CLOSED UPPER LOW THAT TREKS ACROSS NRN AZ DURING THE DAY. STRONGER
DYNAMICS ARE BEING ADVERTISED...AS THE H3 JET DIVES FURTHER TO THE
SOUTH PUTTING SOUTH CENTRAL AZ UNDER THE FAVORED FRONT LEFT QUAD OF
THE JET. ALSO...AN IMPRESSIVE BULLSEYE OF MID LEVEL Q CONVERGENCE IS
FORECAST TO PUSH ACROSS MUCH OF CENTRAL AND NORTHERN AZ. WITH TEMPS
BEING MUCH COOLER RH VALUES WILL BE HIGHER...AND IT WILL BE EASIER
TO WRING SMALLER AMOUNTS OF QPF OUT OF THE ATMOSPHERE. AS SUCH WE
RAISED POPS INTO THE 15-20 PERCENT BALLPARK OVER SOUTH CENTRAL AZ ON
SUNDAY...INCLUDING THE LOWER DESERT AREAS. HIGH TEMPS ARE EXPECTED
TO DROP ANOTHER 10 DEGREES OR SO WITH HIGHS IN THE GREATER PHOENIX
AREA TO FALL TO NEAR 70 DEGREES. THOSE NUMBERS WOULD REPRESENT HIGHS
MORE THAN 10 DEGREES BELOW SEASONAL NORMALS.

BY MONDAY MORNING THE TROF AXIS WILL HAVE SHIFTED SOUTHEAST OF THE
GREATER PHOENIX AREA...PUTTING MOST OF THE CWA UNDER A SUBSIDENT
NORTHWEST FLOW ALOFT. MOISTURE WILL CONTINUE TO THIN...WITH SKIES TO
BECOME MOSTLY SUNNY BY EARLY AFTERNOON OVER ALL BUT THE HIGH TERRAIN
OF SRN GILA COUNTY. LITTLE CHANGE IN HIGH TEMPS IS EXPECTED...AS
COOLER AIR CONTINUES TO FILTER OVER THE LOWER DESERTS. THE FORECAST
HIGH FOR PHOENIX MONDAY WILL BE JUST 72 DEGREES.

DRY NORTH TO NORTHEAST FLOW ALOFT CONTINUES ACROSS THE AREA IN THE
WAKE OF THE DEPARTED UPPER TROF ON TUESDAY...FOR GENERALLY SUNNY
SKIES. HIGH TEMPS WILL RISE A FEW DEGREES AS HEIGHTS/THICKNESSES
START TO CLIMB...BUT OVERALL TEMPS WILL STAY BELOW SEASONAL NORMALS
WITH PHOENIX SITTING IN THE MID TO UPPER 70S.

QUITE A BIT OF MODEL UNCERTAINLY DEVELOPING FOR THE LATTER PORTION
OF THE EXTENDED PERIOD. GFS KEEPS HIGH PRESSURE ALOFT IN PLACE
ACROSS THE DESERT SOUTHWEST...AND DEVELOPS A CLOSED LOW WELL OFF TO
THE SOUTHEAST...OVER PORTIONS OF TEXAS AND NRN MEXICO. ON THE OTHER
HAND...THE ECMWF DEVELOPS THAT SAME UPPER LOW MUCH FURTHER TO THE
WEST...AND ACTUALLY MOVES THE LOW CENTER INTO SERN AZ BY WED
AFTERNOON. THE LOW STARTS TO ADVECT QUITE A BIT OF MOISTURE INTO
SERN AZ...SOME OF THAT MOISTURE TROPICAL IN NATURE. VERY LOW
CONFIDENCE IN THE ECMWF SOLUTION AS MODEL RUN TO RUN CONSISTENCY HAS
BEEN VERY LOW. FOR NOW...WILL KEEP A DRY FORECAST IN PLACE ACROSS AZ
FOR WEDNESDAY AND THURSDAY...BUT WILL KEEP SOME SINGLE DIGIT POPS IN
PLACE FROM PHOENIX EASTWARD...AND ADD IN SOME CLOUD COVER AS
WELL...IN A NOD TO THE MODEL UNCERTAINTY.

&&

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

PERIODIC MID AND HIGH CLOUDS TO AFFECT THE REGION THROUGH THE PERIOD
AS LOW PRESSURE APPROACHES. WINDS ACROSS THE PHOENIX AREA ARE
EXPECTED TO REMAIN OUT OF THE EAST FOR THE MAJORITY OF THE PERIOD
WITH THE POSSIBILITY OF GOING VARIABLE OR SWITCHING OUT OF THE WEST
FOR AN HOUR OR TWO LATE THIS AFTERNOON. WINDS ACROSS SOUTHEAST
CALIFORNIA WILL BECOME BREEZY LATE THIS AFTERNOON AND EVENING WITH
GUSTY WESTERLY WINDS AT KIPL LIKELY PERSISTING THROUGH THE OVERNIGHT
HOURS TONIGHT.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
SLIGHTLY COOLER THAN NORMAL TEMPERATURES WILL FILTER INTO THE
DISTRICT THE FIRST PART OF NEXT WEEK...BEFORE MODERATING THE LATTER
HALF OF THE WEEK. OCCASIONALLY GUSTY AFTERNOON NORTHWEST AND WEST
WINDS WILL BE COMMON SUNDAY AND MONDAY...WITH GUSTS TO AROUND 25 MPH
POSSIBLE ALONG RIDGE TOPS AND THROUGH FAVORED RIVER VALLEY
LOCATIONS. MINIMUM RELATIVE HUMIDITY VALUES WILL INITIALLY HOVER IN
A 20-40 PERCENT RANGE SUNDAY BUT WILL FALL INTO THE TEENS THE
REMAINDER OF THE WEEK AS DRIER AIR GRADUALLY OVERSPREADS THE AREA.
OTHERWISE...OVERNIGHT RECOVERY WILL BE GOOD WITH ONLY MINIMAL
CHANCES OF WETTING RAINS OVER HIGHER TERRAIN EARLY NEXT WEEK.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...CB
AVIATION...KUHLMAN
FIRE WEATHER...MO





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