Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 210303
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
805 PM MST SUN APR 20 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE AREA EARLY THIS WEEK LEADING TO
SUNNY DAYS...CLEAR NIGHTS...AND SHARPLY WARMER AFTERNOON HIGH
TEMPERATURES. BREEZY TO WINDY CONDITIONS WILL DEVELOP OVER MUCH OF
THE AREA TUESDAY AFTERNOON INTO WEDNESDAY AS A DRY WEATHER SYSTEM
PASSES TO THE NORTH. TEMPERATURES WILL FALL ONLY SLIGHT IN RESPONSE
TO THIS WEATHER SYSTEM...CLOSER TO SEASONAL NORMALS FOR THE
REMAINDER OF THE WEEK.

&&

.DISCUSSION...
CLEARING SKIES WERE NOTED OVER THE FORECAST AREA AT 03Z. A HIGH
PRESSURE SYSTEM IS STILL FORECAST TO BUILD OVER THE REGION
MONDAY...FOLLOWED BY A VERY STRONG PACIFIC STORM INTO THE WESTERN
STATES TUESDAY. THE TUESDAY SYSTEM WILL BE POTENT FOR PLACES OVER
NORTHERN/CENTRAL NEVADA/UTAH TUESDAY AFTERNOON...HOWEVER OVER OUR
FORECAST AREA...SOUTHEAST CA TO SOUTH CENTRAL AZ...DRY AND WINDY
WEATHER WITH CONSIDERABLE HIGH CLOUDS ARE EXPECTED. ALSO IN OUR
FORECAST AREA TUESDAY...THERE IS POTENTIAL FOR WIND GUSTS IN THE 25
TO 35 MPH RANGE AREA-WIDE WHICH HAVE IMPLICATIONS FOR BLOWING
DUST...AND ENHANCED FIRE WEATHER DANGER. CURRENT FORECASTS LOOK OK
FOR NOW. NO UPDATES PLANNED. PREVIOUS DISCUSSION BELOW STILL APPLIES.


.PREVIOUS DISCUSSION...145 PM MST...
DESPITE A RATHER SUBSIDENT...DRY NORTHWEST FLOW ACROSS AZ ON THE
BACKSIDE OF A DEPARTING UPPER LOW...SUFFICIENT BOUNDARY LAYER
MOISTURE...SUNSHINE...INSTABILITY AND WEAK UPPER CYCLONIC FLOW HAVE
COMBINED TO PRODUCE CONSIDERABLE CU ACROSS THE MOGOLLON RIM AND
WHITE MOUNTAINS THIS AFTERNOON. IN FACT...IR IMAGERY EVEN SHOWED A
BIT OF FAIR WEATHER CU FORMING OVER HIGHER ELEVATION LOCATIONS
ACROSS THE LOWER DESERT. WE MAY SEE AN ISOLATED HIGH BASED
THUNDERSTORM DRIFT OFF THE ERN RIM AND INTO THE ERN PORTIONS OF ZONE
24 LATER THIS AFTERNOON AND EARLY EVENING...MAINLY AFFECTING AREAS
TO THE EAST OF GLOBE AND PUNKIN CENTER. OTHERWISE EXPECT SKIES
BECOMING GENERALLY CLEAR EARLY THIS EVENING AFTER SUNSET AND THE
ASSOCIATED LOSS OF SOLAR INSOLATION.

UPPER LEVEL HIGH PRESSURE RIDGE WILL BUILD INTO THE DESERT SOUTHWEST
ON MONDAY...LEADING TO SOME MORE WARMING WITH HIGH TEMPS OVER THE
WARMER DESERTS RISING INTO THE MID 90S TO NEAR 100 DEGREES...UNDER
GENERALLY SUNNY SKIES.

GUIDANCE REMAINS QUITE CONSISTENT IN CALLING FOR A RATHER VIGOROUS
AND PROGRESSIVE OPEN WAVE UPPER TROF TO MOVE ACROSS THE AREA TUESDAY
THROUGH THE DAY ON WEDNESDAY...BRINGING BREEZY TO WINDY CONDITIONS
ALONG WITH A COOLING TREND...BUT NO PRECIP. THIS IS A VERY TYPICAL
WEATHER PATTERN FOR LATE APRIL...HAVING THE TROF PASS TO THE NORTH
WITH DRY CONDITIONS SEEN ACROSS THE LOWER ARIZONA DESERT. THE MOST
SIGNIFICANT WIND WILL OCCUR TUESDAY AFTERNOON AND EVENING...MAINLY
ACROSS THE WESTERN DESERTS AND HIGHER TERRAIN AREAS OF JOSHUA TREE
NATIONAL PARK. ATTM IT APPEARS THE WINDS WILL REMAIN A BIT BELOW
WIND ADVISORY LEVELS...BUT COMBINED WITH DRIER AIR MOVING IN WE WILL
LIKELY HAVE FIRE WEATHER CONCERNS...AND A FIRE WEATHER WATCH MAY
NEED TO BE ISSUED WITHIN THE NEXT 24 HOURS. OTHERWISE...EXPECT
COOLER CONDITIONS ON WEDNESDAY WITH HIGH TEMPS DROPPING FROM THE MID
TO UPPER 90S DOWN INTO THE MID TO UPPER 80S OVER THE LOWER DESERTS.
LESS WIND IS EXPECTED WEDNESDAY HOWEVER IT WILL STILL BE ON THE
BREEZY SIDE DURING THE AFTERNOON HOURS.

THE LOW LEVEL FRONTAL PASSAGE SHOULD CLEAR THE FORECAST AREA
WEDNESDAY MORNING...WITH MODEST HEIGHT FALLS AND SFC-H7 CAA. THIS
WILL ONLY BE SUFFICIENT TO COOL THE REGION BACK TOWARDS THE
CLIMATOLOGICAL NORMAL WEDNESDAY AFTERNOON...WITH SHORTWAVE RIDGING
AND H5 HEIGHTS REBOUNDING AOA 576DM BY THURSDAY AND FRIDAY. ENSEMBLE
SPREAD CONTINUES TO GROW FOR THE WEEKEND TIME FRAME WITH EACH
FORECAST ITERATION. THE MODEL TREND OF NEGATIVE HEIGHT ANOMALIES
COVERING THE NORTHEAST PACIFIC BASIN REMAINS CONSISTENT...HOWEVER
THE SUBSEQUENT PROGRESSION OF SHORTWAVES INTO THE WRN/CNTRL CONUS IS
HIGHLY UNCERTAIN.

OPERATIONAL MEMBERS HAVE RETAINED GOOD RUN TO RUN CONTINUITY...WITH
THE GFS BODILY DEEPENING A SIGNIFICANT SINGLE WAVE INTO THE SWRN
CONUS OVER THE WEEKEND...WHILE THE ECMWF EJECTS SEVERAL WEAKER LEAD
WAVES THROUGH THE DOWNSTREAM QUASI-ZONAL FLOW WHILE MAINTAINING
GENERAL EAST PACIFIC TROUGHING. THE OPERATIONAL GEM IS SOMEWHAT OF
A COMPROMISE OF THESE TWO EXTREMES...BUT TENDS TO EVENTUALLY FAVOR
SOME MEASURE OF DEEPER TROUGHING NEAR THE FORECAST AREA. ENSEMBLE
MEMBERS EXHIBIT A VAST ARRAY OF POSSIBLE OUTCOMES...RESULTING IN
VERY LOW FORECAST CONFIDENCE NEXT WEEKEND. AT THIS TIME...UNLESS THE
SYSTEM DIGS EVEN DEEPER TO THE WEST OF CALIFORNIA...COULD NOT ARGUE
FOR HIGHER PRECIPITATION CHANCES WITH THE CURRENT SHORTWAVE
PROPAGATION TRAJECTORIES (THATS NOT TO SAY IT COULDN/T HAPPEN...JUST
VERY DIFFICULT THIS TIME OF YEAR). RATHER...THE PRIMARY FORECAST
CHALLENGE WILL BE DETERMINING IF/WHEN PRONOUNCED COOLING AFFECTS THE
REGION.

&&

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

THROUGH 19Z MON...CLEAR SKIES. LIGHT AND VRBL WIND UNDER 8 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
BUILDING HIGH PRESSURE WILL MOVE IN STARTING WEDNESDAY...BUT
WIDESPREAD BREEZY CONDITIONS WILL STILL PERSIST MUCH OF WEDNESDAY AS
THE GRADIENT REMAINS SOMEWHAT TIGHT BEHIND THE EXITING LOW PRESSURE
SYSTEM. AFTER LIGHT WINDS ON THURSDAY...BREEZY CONDITIONS RETURN FOR
FRIDAY AND SATURDAY AS ANOTHER PACIFIC LOW PRESSURE SYSTEM NEARS THE
REGION. DRY CONDITIONS ALONG WITH NEAR TO SLIGHTLY ABOVE NORMAL
TEMPERATURES ARE EXPECTED THROUGH THE COMING WEEKEND. MINIMUM
HUMIDITIES WILL BE IN THE SINGLE DIGITS ACROSS THE LOWER DESERTS
THROUGH FRIDAY...BEFORE SEEING AN UPTICK FOR THE WEEKEND WITH VALUES
MAINLY IN THE TEENS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...VASQUEZ/CB/MO
AVIATION...VASQUEZ
FIRE WEATHER...CK













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