Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 200417
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
920 PM MST SUN OCT 19 2014

.SYNOPSIS...
ISOLATED THUNDERSTORMS WILL LINGER THROUGH MONDAY ACROSS THE
MOUNTAINS NORTH AND EAST OF PHOENIX. ANOTHER TROUGH WILL MOVE
THROUGH THE AREA ON TUESDAY HOWEVER ONLY A FEW CLOUDS ARE EXPECTED
WITH THIS SYSTEM. CONDITIONS WILL WARM UP BY MID WEEK INTO NEXT
WEEKEND AS HIGH PRESSURE SETTLES OVERHEAD.

&&

.DISCUSSION...
THUNDERSTORM COVERAGE THIS AFTERNOON AND EVENING WAS MORE
REMINISCENT OF THE MONSOON...THOUGH THE CHARACTER OF THE STORMS WAS
DEFINITIVELY FALL-LIKE WITH 500 MB TEMPERATURES AS COLD AS -15C.
CONVECTION INITIALLY DEVELOPED ACROSS EASTERN PINAL AND SOUTHERN
GILA COUNTIES THIS AFTERNOON...PRODUCING SMALL HAIL AND AREAS OF
HEAVY RAIN AND MINOR FLOODING. AN OUTFLOW BOUNDARY PROPAGATING FROM
SE AZ THEN COLLIDED WITH A GUST FRONT DROPPING SOUTHWESTWARD FROM
NORTHEASTERN MARICOPA COUNTY. CONSEQUENTLY...STRONG LOW-LEVEL
CONVERGENCE PROVIDED THE NECESSARY ASCENT FOR STORMS TO DEVELOP
ACROSS THE PHOENIX AREA...DESPITE LIMITED INSTABILITY AND INCREASING
INHIBITION. RAIN TOTALS WERE GENERALLY AROUND A TENTH OF AN
INCH...EXCEPT IN SCOTTSDALE WHERE SOME AREAS RECEIVED OVER A HALF OF
AN INCH.

IT IS INTERESTING TO NOTE THAT CLOUD TOP TEMPERATURES ON
IR SATELLITE ONLY REACHED -29C...WHICH CORRESPONDS TO ROUGHLY 350 MB
OR 25-30K FEET ON THE FGZ/TWC SOUNDINGS AND RIGHT AT THE BASE OF THE
UPPER-LEVEL SUBSIDENCE INVERSION. IT IS THIS INVERSION ASSOCIATED
WITH A BUILDING UPPER-LEVEL RIDGE THAT PREVENTED STORMS FROM
REACHING SEVERE THRESHOLDS.

REST OF TONIGHT...MID-TROPOSPHERIC LOW ACROSS NORTHERN SONORA WILL
CONTINUE TO MIGRATE EASTWARD. GLOBAL AND CONVECTIVE-ALLOWING MODELS
INDICATE THAT ISOLATED CONVECTION ACROSS THE LOWER DESERTS WILL
DISSIPATE AS WELL. MINOR ADJUSTMENTS TO THE FORECAST WILL BE NEEDED
TO ACCOUNT FOR RECENT DOWNWARD TRENDS.

&&

.PREVIOUS DISCUSSION...
WEAK CYCLONIC FLOW WILL REMAIN IN PLACE ACROSS THE SOUTHWEST ON
MONDAY...BUT WILL BE DISPLACED WELL TO THE EAST COMPARED TO TODAY.
ADDITIONAL SHOWERS AND STORMS WILL BE POSSIBLE ACROSS THE HIGHER
TERRAIN BUT THE VAST MAJORITY OF THE ACTIVITY SHOULD BE INTO NEW
MEXICO BY MONDAY AFTERNOON. ALL OF THE HI-RES MODELS AS WELL AS THE
USUALLY WET SREF GUIDANCE AGREES WITH THIS ASSESSMENT AND ASIDE FROM
A FEW ISOLATED SHOWERS AROUND GLOBE/HILLTOP/ROOSEVELT...IT SHOULD BE
RELATIVELY QUIET. STRONG SUBSIDENCE IN THE 500-300MB LAYER SHOULD
ALSO LIMIT STORM COVERAGE/INTENSITY.

ON TO TUESDAY AS A TROUGH PRESENTLY LOCATED OVER THE PAC NW MOVES
INLAND THROUGH UTAH. A FEW DAYS AGO THIS TROUGH WAS EXPECTED TO MOVE
THROUGH PORTIONS OF ARIZONA BUT THE NORTHWARD TREND REMAINS ON
TRACK. VERY SLIM CHANCES OF SHOWERS WITH THIS SYSTEM EAST OF PHOENIX
AND VIRTUALLY NO CHANCE WHATSOEVER ACROSS THE LOWER DESERTS. SHOULD
ONLY SEE A BRIEF INCREASE IN CLOUDS DURING THE DAY ON TUESDAY
FOLLOWED BY CLEARING TUESDAY NIGHT.

LOOKING AHEAD FROM WEDNESDAY INTO THE WEEKEND...RIDGING WILL SET UP
YIELDING DRY WEATHER ACROSS THE ENTIRE AREA.
MEANWHILE...TEMPERATURES WILL BEGIN AN UPWARD CLIMB INTO THE MID 90S
WHICH IS JUST ABOUT 10 DEGREES ABOVE NORMAL FOR LATE OCTOBER. THE
RIDGE WILL BREAK DOWN BY SATURDAY/SUNDAY YIELDING SLIGHTLY COOLER
TEMPERATURES BUT STILL WARMER THAN NORMAL.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL...
SCT-BKN CLOUD DECKS GENERALLY AOA 9KFT WILL PERSIST INTO THE EVENING
HOURS...ALONG WITH ISOLATED THUNDERSTORMS EAST AND SOUTH OF THE
TERMINALS PERSISTING UNTIL AROUND SUNSET. GUSTY OUTFLOW FROM
VICINITY STORMS IS POSSIBLE THROUGH UNTIL 01Z...ESPECIALLY NEAR
KIWA...BUT OVERALL WINDS SHOULD REMAIN LIGHT AND VARIABLE FAVORING
EAST OVERNIGHT INTO MONDAY MORNING. CLOUD DECKS WILL THIN OUT LATER
THIS EVENING...WITH SOME DEBRIS REMAINING INTO MONDAY MORNING.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
MAINLY CLEAR SKIES WITH LIGHT AND VARIABLE WINDS EXPECTED THROUGH
THE PERIOD.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
A GRADUAL DRYING TREND IS EXPECTED THE LATER HALF OF THE WEEK...WITH
MINIMUM HUMIDITY LEVELS GRADUALLY TRENDING DOWN INTO THE TEENS BY
THE WEEKEND. WINDS WILL BE GENERALLY LIGHT AND FOLLOW TYPICAL
DIURNAL PATTERNS EACH DAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...LEINS
AVIATION...MEYERS
FIRE WEATHER...MEYERS






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