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000
FXUS65 KPSR 250459
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1000 PM MST FRI MAY 24 2013

.SYNOPSIS...
LOW PRESSURE CENTER OVER THE PACIFIC NORTHWEST IS EXPECTED TO KEEP
THE REGION UNDER DRY SOUTHWESTERLY FLOW ALOFT...WITH BREEZY
CONDITIONS AT TIMES INTO NEXT WEEK. ANTICIPATE LITTLE CHANGE IN
TEMPERATURES THROUGH SUNDAY. THEREAFTER...A TROUGH ALONG THE
WEST COAST IS ANTICIPATED TO DEEPEN WHICH WILL LEAD TO SOME MODEST
COOLING MONDAY WITH SOME MORE NOTICEABLE COOLING TUESDAY AND
WEDNESDAY.

&&

.DISCUSSION...
DOMINANT SOUTHWEST FLOW CONTINUES TO SPREAD MOSTLY DRY AREA ACROSS
THE REGION WITH LINGERING EVENING BREEZINESS. PAC NW LOW HAS
EXPANDED NORTHWARD INTO CANADA...WITH LONGWAVE TROUGHING EXPANDING
DOWN INTO THE INTERMOUNTAIN WEST. PERSISTENCE WILL REIGN OVER THE
FORECAST...WITH CONTINUED AFTERNOON BREEZINESS AND MILD LATE MAY
TEMPERATURES THROUGH THE HOLIDAY WEEKEND. NO MAJOR UPDATES PLANNED
TO THE FORECAST GRIDS TONIGHT...JUST MINOR TWEAKS TO TREND THE GRIDS
CLOSER TO EVENING OBSERVATIONS.

&&

.PREVIOUS DISCUSSION /ISSUED 150 PM MST/PDT/...
FOR THE NEXT FEW DAYS...NO SIGNIFICANT CHANGES TO THE WEATHER
PATTERN ARE EXPECTED...AT LEAST NONE THAT WILL CHANGE OUR SENSIBLE
WEATHER VERY MUCH. A SERIES OF PV ANOMALIES/VORT MAXES ROTATE AROUND
THE MAIN UPPER LOW AND INTO THE PAC NW...KEEPING PERSISTENT SWLY
FLOW ALOFT IN PLACE ACROSS ARIZONA THRU THE WEEKEND AND INTO EARLY
NEXT WEEK. H5 HEIGHTS/THICKNESSES CHANGE LITTLE OVER THIS TIME AND
AS SUCH HIGH TEMPS WILL REMAIN IN THE MID 90S TO AROUND 100 SATURDAY
INTO NEXT MONDAY. PROGS INDICATE THAT THERE WILL BE AN INCREASE IN
HIGH CLOUDS MONDAY FOR PARTLY SUNNY SKIES...BUT UNTIL THEN EXPECT
MOSTLY SUNNY OR SUNNY DAYS AND CLEAR NIGHTS. AFTERNOON AND EARLY
EVENING BREEZES WILL BE ON TAP TONIGHT INTO MONDAY AS WELL AS MID
LEVEL GRADIENTS REMAIN SOMEWHAT TIGHT.

PROGS AGREE THAT A LARGE AND RATHER PROGRESSIVE UPPER TROF WILL
DEVELOP ALONG THE PAC NW COAST...THEN SLIDE SOUTHEASTWARD AND INTO
OUR REGION BY NEXT TUESDAY. MODEL DIFFERENCES ARE STILL PROBLEMATIC
WITH THE OPERATIONAL EUROPEAN LIKELY ON THE OVERLY STRONG AND WET
SIDE OF THE SPECTRUM AND THE GEM ON THE OPPOSITE SIDE OF THE
SPECTRUM WITH THE MAIN SHORTWAVE ENDING UP ACROSS THE PACIFIC
NORTHWEST. THE EUROPEAN AND GFS ENSEMBLE MEANS ARE FAIRLY CLOSE TO
EACH OTHER IN SPEED AND STRENGTH WITH MORE SPREAD SEEN WITHIN THE
EUROPEAN ENSEMBLE MEMBERS. GIVEN THIS...HAVE TRENDED THE CURRENT
FORECAST TOWARD THE GFS...GFS ENSEMBLE MEAN...AND EUROPEAN ENSEMBLE
MEAN. THIS STILL RESULTS IN A MODEST COOLDOWN OF 5-10 DEGREES FOR
THE MIDDLE OF NEXT WEEK...AND ESPECIALLY TUESDAY AND WEDNESDAY WITH
THE POTENTIAL FOR DECENT MID AND HIGH LEVEL MOISTURE AND RESULTING
CLOUD COVER. PRECIPITATION CHANCES STILL LOOK FAIRLY LOW GIVEN
OVERALL FAIRLY DRY AIRMASS...WHICH WOULD BE LIKELY GIVEN THE TIME OF
YEAR AND VERY LOW POPS EXPECTED BY CLIMO. HAVE ELECTED TO MOSTLY
IGNORE THE OPERATIONAL EUROPEAN QPF FORECAST FOR THE REGION GIVEN
IT/S OVERLY STRONG SOLUTION...BUT HAVE AT LEAST INCLUDED SLIGHTLY
HIGHER THAN CLIMO POPS FOR TUESDAY INTO WEDNESDAY. IF OTHER MODEL
SOLUTIONS START TRENDING TOWARD THE STRONGER EUROPEAN...HIGHER POPS
WILL BE NEEDED.

DRY WESTERLY FLOW ALOFT WILL FOLLOW ON THURSDAY FOR MOSTLY SUNNY
SKIES...ALONG WITH WARMING TEMPERATURES.

&&

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

DRY SOUTHWEST FLOW ALOFT WILL CONTINUE MOSTLY CLEAR SKIES AND
ELEVATED EVENING BREEZINESS THROUGH THE LATE EVENING. WINDS FOR THE
PHX TERMINALS WILL GRADUALLY DECREASE TO VRB BEFORE PICKING UP
TYPICAL EASTERLY DRAINAGES WHILE KIPL AND KBLH WILL CONTINUE
SOUTHWEST-WEST HEADINGS WITH PERIODIC GUSTS UP TO 20KTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
LARGE AREA OF ALMOST STATIONARY LOW PRESSURE ACROSS THE NORTHWEST
U.S. WILL BEGIN TO OPEN UP INTO A MORE NOTICEABLE TROUGHING PATTERN
BY MONDAY. A SERIES OF DRY WEATHER SYSTEMS WILL MOVE THROUGH THE
PREDOMINATELY SOUTHWEST FLOW...PERSISTING AFTERNOON AND EARLY
EVENING WINDS WHILE ALSO INTRODUCING A MILD COOLING TREND. WITH
CURRENT FORECAST MODEL GUIDANCE...WINDS LOOK TO BE THEIR STRONGEST
LATE TUESDAY INTO WEDNESDAY...HOWEVER AT THIS TIME REMAINING BELOW
CRITICAL FIRE WEATHER THRESHOLDS. HUMIDITIES WILL SEE A SLIGHT
INCREASE MIDWEEK WITH THE COOLER TEMPERATURES AND POTENTIAL FOR SOME
WEAK LOW LEVEL MOISTURE ADVECTION...AHEAD OF THE MOST PROMISING
WEATHER SYSTEM ATTM. OVERALL...CONDITIONS FOR THE SOUTHWEST FIRE
DISTRICTS WILL REMAIN DRY AS DRY WESTERLY FLOW RETURNS TO THE REGION
LATE WEEK. NEAR NORMAL TEMPERATURES WITH A RETURN TO SINGLE DIGIT
DAYTIME HUMIDITIES ARE EXPECTED.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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DISCUSSION...NOLTE
PREVIOUS DISCUSSION...CB/KUHLMAN
AVIATION...NOLTE
FIRE WEATHER...NOLTE