Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 172113
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
213 PM MST THU APR 17 2014

.SYNOPSIS...
A PACIFIC STORM WILL MOVE INTO THE AREA STARTING TONIGHT BRINGING
INCREASING MOISTURE AND CLOUDS. BY FRIDAY AFTERNOON THIS SYSTEM WILL
SUPPORT SLIGHT CHANCES FOR SHOWERS FROM THE COLORADO RIVER EAST
ACROSS SOUTH CENTRAL ARIZONA AND INTO THE HIGHER TERRAIN. DAYTIME
TEMPERATURES FOR FRIDAY AND SATURDAY WILL FALL TO MORE SEASONAL
VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE EAST ON
SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR EARLY NEXT
WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
HIGH THIN CLOUDS ARE STARTING TO OVERSPREAD SOUTHEAST CALIFORNIA
INTO SOUTHWEST ARIZONA THIS AFTERNOON. CURRENT WATER VAPOR IMAGERY
AND OBJECTIVE ANALYSIS SHOWS AN UPPER LEVEL LOW CIRCULATION NEAR
31N/124W WITH EXTENSIVE MOISTURE AHEAD OF THE LOW AND SOME
SUB-TROPICAL MOISTURE WRAPPING INTO THE LOW FROM THE SOUTHWEST. AS
THE LOW APPROACHES THE DESERT SOUTHWEST TONIGHT...EXPECT CLOUDS TO
THICKEN FROM THE SOUTHWEST TO THE NORTHEAST LATE TONIGHT INTO FRIDAY
MORNING. SKIES WILL LIKELY BECOME MOSTLY CLOUDY AND POSSIBLY CLOUDY
AT TIMES DURING MUCH OF THE DAYTIME HOURS FRIDAY. MODELS SHOW WEAK
TO MODERATE DIFLUENCE ALOFT AND SUFFICIENT OMEGA IN A NEAR
SATURATED 600-400MB LAYER STARTING FRIDAY MORNING. AM EXPECTING SOME
HIGH BASED...12-15K FEET...SHOWERS TO DEVELOP SOMETIME FRIDAY
MORNING INTO EARLY FRIDAY AFTERNOON...ESPECIALLY ALONG AND JUST
BEHIND THE LEADING EDGE OF THE MID LEVEL MOISTURE PLUME. SINCE THE
SUB-CLOUD LAYER WILL BE DRY...NOT QUITE BONE DRY...NOT EXPECTING TOO
MANY LOCATIONS TO SEE RAIN HITTING THE GROUND...MAINLY HIGHER
TERRAIN LOCALES.

CHANCES INCREASE FRIDAY AFTERNOON AND EARLY FRIDAY EVENING...BUT
OVERALL COVERAGE WILL BE LIMITED AND POPS STILL ONLY IN THE SLIGHT
CHANCE CATEGORY AND MAINLY COVERING THE HIGHER TERRAIN. THE WARM AND
DRY SUB-CLOUD LAYERS MAY BRING THE POTENTIAL FOR GUSTY WINDS AND
OUTFLOWS IF A STORM GETS ORGANIZED ENOUGH. THE MAIN UPPER LOW
CIRCULATION WILL HANG BACK ACROSS SOUTHEAST CALIFORNIA FRIDAY
AFTERNOON...THEN SLOWLY PROGRESSING INTO CENTRAL ARIZONA DURING THE
DAY SATURDAY. SLIGHT CHANCE POPS WILL REMAIN THROUGH FRIDAY NIGHT
INTO SATURDAY EVENING ACROSS SOUTH-CENTRAL ARIZONA WITH CHANCE POPS
ACROSS THE HIGHER TERRAIN IN GILA COUNTY. QPF AMOUNTS FOR THE ENTIRE
EVENT WILL BE NEAR ZERO ACROSS THE LOWER DESERTS TO AROUND A TENTH
OF AN INCH ACROSS GILA COUNTY.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A GRADUAL INCREASE IN MID AND HIGH CLOUDS IS EXPECTED OVER THE NEXT
24 HOURS AHEAD OF A LOW PRESSURE SYSTEM. WITH THE LOW IN OUR
VICINITY...WINDS WILL ALSO RETAIN MORE OF A SOUTHERLY COMPONENT
THROUGH FRIDAY AFTERNOON. HOWEVER...THROUGH 18Z FRIDAY...WINDS WILL
REMAIN DIURNAL AND GENERALLY LESS THAN 10 KT. GIVEN THE DRY
CONDITIONS NEAR THE SURFACE...THERE ALSO IS THE POTENTIAL FOR VIRGA
PRODUCING LOCALIZED DOWNBURST WINDS...PERHAPS AS EARLY AS FRIDAY
MORNING BUT MORE LIKELY FRIDAY AFTERNOON.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHERLY WINDS WILL BE THE PRIMARY AVIATION WEATHER IMPACT...WITH
OCCASIONAL GUSTS TO AROUND 20 KT THIS AFTERNOON. WINDS WILL ABATE
OVERNIGHT BEFORE INCREASING AGAIN FRIDAY AFTERNOON AHEAD OF A LOW
PRESSURE SYSTEM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN/NOLTE
AVIATION...HIRSCH
FIRE WEATHER...HIRSCH







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