Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 310321
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
820 PM MST FRI JAN 30 2015

...UPDATED AVIATION AND PUBLIC DISCUSSIONS...

.SYNOPSIS...
AREAS OF SHOWERS WILL CONTINUE TO BE LIKELY OVER PARTS OF EASTERN
AND NORTHERN ARIZONA TONIGHT...ESPECIALLY OVER HIGHER TERRAIN...AND
LESS LIKELY OVER SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA. RAIN
SHOWER CHANCES WILL CONTINUE FOR MUCH OF THE DAY SATURDAY BEFORE
DIMINISHING SATURDAY NIGHT. A RETURN TO DRY WEATHER AND A SLOW
WARMING TREND WILL BEGIN SUNDAY AND CONTINUE THROUGH NEXT WEEK.

&&

.DISCUSSION...
THE LOCAL FORECAST AREA IS TRAPPED BETWEEN 3 DISTINCT SHORTWAVES/PV
ANOMALIES EARLY THIS EVENING. THE INITIAL WAVE LIFTING TOWARD LAS
VEGAS HAS BEEN WEAKENING AND FILLING TODAY...WHILE A MORE DYNAMIC
WAVE WAS DIGGING THROUGH THE TROUGH BASE IN THE CNTRL BAJA
PENINSULA. A TRAILING WAVE DIVING THROUGH THE WRN PERIPHERY OF THE
ENTIRE TROUGH COMPLEX WAS SUPPORTING SHOWERS ALONG THE SRN
CALIFORNIA COAST. CONCURRENTLY...DEEPER MOISTURE ADVECTION AND A
MERIDIONAL JET WAS SHIFTING THE MORE SOLID SHIELD OF RAINFALL INTO
ERN ARIZONA...WHILE MORE ISOLD/SCT LIGHTER SHOWERS WERE PERCOLATING
WITHIN THE CYCLONIC COLD CORE.

FORECAST THROUGH THE NIGHT IS NOW BASED ON RECENT HRRR
OUTPUT...SUPPORTING 4KM WRF-ARW AND WRF-NMM MEMBERS...AND CURRENT
RADAR TRENDS. CONSENSUS APPEARS THAT SHOWERS THROUGH CNTRL ARIZONA
WILL EBB THROUGH THE NIGHT IN A MOIST ENVIRONMENT...THOUGH COVERAGE
WILL REMAIN SCT AS ASCENT FIELDS ARE NOT AS ORGANIZED (THOUGH
CERTAINLY NOT IN A REALM OF SUBSIDENCE). SOME FURTHER REFINEMENTS
ARE LIKELY TO ADDRESS ACTIVITY COMING OUT OF WRN PIMA
COUNTY...THOUGH THE OVERALL TREND ARGUED FOR A MODEST REDUCTION OVER
MOST LOCATIONS. AS THE AFOREMENTIONED SRN CALIFORNIA WAVE PHASES
WITH THE BAJA WAVE LATE TONIGHT...ANOTHER CHANCE OF BETTER ORGANIZED
LIFT SHOULD MOVE TOWARDS CNTRL ARIZONA. SOME QUESTION AS TO HOW FAR
NORTH THE RAIN SHIELD WILL GET AS THE ENTIRE COLD CORE STRUCTURE
SHIFTS SOUTH...BUT KEPT SOME RATHER HEALTHY CHANCES ADVERTISED
SATURDAY MORNING.

&&

.PREVIOUS DISCUSSION...
REST OF TODAY THROUGH SATURDAY...
YET ANOTHER VORT MAX ROUNDS THE BOTTOM OF THE UPPER TROUGH LATE
TONIGHT AND BEGINS AFFECTING SOUTHERN ARIZONA SATURDAY MORNING.
LOOKS LIKE SOUTHEAST ARIZONA WILL SEE MOST OF THE PRECIP FROM THAT
FEATURE BUT DEPICT SOME NOTABLE QPF SPREADING WELL INTO
SOUTH-CENTRAL ARIZONA. THUS WE MAY HAVE ANOTHER ROUND OF WIDESPREAD
SHOWERS BEFORE A DOWNTREND BEGINS IN THE AFTERNOON.
OVERALL...ANTICIPATE LESS DYNAMICAL LIFT TONIGHT AND SATURDAY
COMPARED TO THE PREVIOUS 24 HOURS...DUE AT LEAST IN PART TO LOSS OF
UPPER DIFFLUENCE/DIVERGENCE. ACCORDINGLY...ANTICIPATE LESS PRECIP
TONIGHT AND SATURDAY THAN WE HAD IN THE PRECEDING 24 HOURS.
ANTICIPATE NUISANCE FLOODING TO CONTINUE...MAINLY OVER HIGHER
TERRAIN AND FOOTHILL AREAS...LESS OVER VALLEY FLOORS OF THE CENTRAL
DESERTS. ONE CAVEAT IS THAT WE COULD HAVE A LITTLE BIT MORE
INSTABILITY IF CLOUDS THIN OUT ENOUGH. NAM HAS BEEN DEPICTING THIS
IDEA. THUS HELD ON TO SLIGHT CHANCE OF THUNDERSTORMS FOR SATURDAY
AFTERNOON. THE SYSTEM BEGINS EXITING SOUTHWARD SATURDAY NIGHT AS A
RIDGE BUILDS IN AND THUS POPS DIMINISH OVERNIGHT SATURDAY.

SUNDAY THROUGH FRIDAY...
SUNDAY LOOKS TO BE A DRY AND WARMER DAY. PATCHY MORNING FOG IS A
POSSIBILITY BUT THERE MAY BE ENOUGH LINGERING CLOUDS TO HINDER THE
RADIATIONAL COOLING NECESSARY. PARED BACK ON THE AREAL COVERAGE TO
REMOVE SOUTHEAST CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY AS
SOME DRY ADVECTION MOVES IN THERE. THE RIDGE SLOWLY BUILDS INTO THE
WEST MONDAY THROUGH THURSDAY FOR A GRADUAL WARMING TREND...AND WE
CAN EXPECT DESERT HIGHS TO REACH BACK INTO THE LOW TO MID 70S BY
NEXT WEDNESDAY...WITH THE WARMER WESTERN DESERTS RISING TO NEAR 80
BY NEXT THURSDAY...LITTLE CHANGE FRIDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL...
SHORT TERM: MODERATE TO GOOD CONFIDENCE THAT WIDESPREAD RAINFALL AND
IFR CIGS HAVE ENDED FOR THE EVENING. HOWEVER...SCT SHOWERS ARE STILL
DEVELOPING SW OF PHOENIX...AND MAY SURVIVE INTO TERMINALS LATER
TONIGHT. VISIBILITIES HAVE IMPROVED...THOUGH MOUNTAIN OBSCURATION
WILL STILL BE A PROBLEM. SOME AREAS OF MVFR CIGS AROUND THE PHOENIX
METRO...AND MAY BEGIN TO FILL IN AS RAIN RE-ENTERS THE AREA LATER
TONIGHT AFTER 06Z.

SAT MORNING-AFTERNOON: LOWER CONFIDENCE THAT RESIDUAL MOISTURE WILL
ALLOW MVFR BR/HZ TO FORM SAT MORNING...AND MAY BE MORE ASSOCIATED
WITH INCOMING NEW ROUND OF RAINFALL. SOMEWHAT BETTER CONFIDENCE THAT
THE NEXT ROUND OF SHOWERS WILL IMPACT TERMINALS IN THE 12Z-18Z TIME
FRAME...WITH ASSOCIATED MVFR VSBY/CIGS LIKELY. ARRIVAL TIME MAY BE
SOONER BASED ON RECENT TRENDS. MORE SCT ACTIVITY SAT AFTERNOON...AND
EVEN AN ISOLD TS MAY BE POSSIBLE...THOUGH CHANCES ARE TOO REMOTE TO
PLACE IN TAF PACKAGE.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SHOWERS SHOULD STAY SOUTH AND WEST OF CALIFORNIA TERMINALS THROUGH
AT LEAST 12Z SAT...THOUGH RESIDUAL MOISTURE COULD FORM LOCAL MVFR
BR/HZ (ESPECIALLY AT THE MORE FAVORED KIPL SITE). SCT SHRA AND
POTENTIALLY BRIEF PERIODS OF MVFR CIGS/VSBY MAY BE POSSIBLE LATER
SATURDAY MORNING AS THE UPPER LOW PIVOTS THROUGH THE AREA...THOUGH
CONFIDENCE IS ONLY LOW TO MODERATE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
DRIER AND SIGNIFICANTLY WARMER WEATHER IS EXPECTED...AS HIGH
PRESSURE BEGINS BUILDING BACK INTO THE REGION. HIGH TEMPERATURES IN
THE LOWER DESERTS WILL START OUT IN THE UPPER 60S ON SUNDAY AND
GRADUALLY CLIMB INTO THE UPPER 70S BY THURSDAY. WINDS ARE EXPECTED
TO BE LIGHT AND VARIABLE FOR MOST OF THE FORECAST PERIOD.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO/AJ/CB
AVIATION...MO
FIRE WEATHER...MCLANE





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