660
FXUS65 KPSR 040315
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
815 PM MST SUN MAR 3 2013


.SYNOPSIS...
A WEAK WEATHER DISTURBANCE WILL MOVE THROUGH NORTHERN ARIZONA TODAY
BRINGING EXTENSIVE CLOUD COVER AND SLIGHTLY COOLER TEMPERATURES TO
THE REGION. PRECIPITATION CHANCES WILL BE CONFINED MAINLY TO THE
HIGHER TERRAIN OF NORTHERN ARIZONA...WITH ONLY A CHANCE FOR A BRIEF
SPRINKLE FURTHER SOUTH. TEMPERATURES WILL REBOUND DURING THE MIDWEEK
TIME FRAME...HOWEVER A MORE SIGNIFICANT COOLING TREND WILL DEVELOP
DURING THE LATTER HALF OF THE WEEK AS LOW PRESSURE SETTLES OVER THE
WESTERN STATES. THIS WEATHER SYSTEM WILL ALSO LEAD TO INCREASED
PRECIPITATION CHANCES NEXT WEEKEND.

&&

.DISCUSSION...
CONSIDERABLE MID AND HIGH CLOUDS...ASSOCIATED WITH A WEAK WEATHER
DISTURBANCE MOVING THROUGH SOUTHERN UTAH AND NORTHERN AZ...CONTINUED
TO STREAM WEST TO EAST ACROSS AZ AT 03Z. A FEW SPRINKLES...BUT
MOSTLY VIRGA SHOWERS...WERE NOTED ON RADAR SUNDAY AFTERNOON...WITH A
FEW LINGERING SPRINKLES THIS EVENING IN THE PHOENIX AREA. AS THE
DISTURBANCE MOVED QUICKLY EAST...CLEARING SKIES WERE NOTED IN
SOUTHEAST CA AND SOUTHWEST AZ AT 03Z...WITH CLEARING EXPECTED IN
CENTRAL AZ INCLUDING PHOENIX AREA BY 07Z.

INCREASING WESTERLY FLOW ALOFT WILL CONTINUE TO SEND A SERIES OF
PACIFIC DISTURBANCES INTO THE WESTERN STATES MAINLY NORTH OF AZ.
ANOTHER ROUND OF MID AND HIGH CLOUDS ARE EXPECTED TUESDAY AFTERNOON
AND NIGHT.

OTHERWISE DRY WEATHER WITH ABOVE NORMAL TEMPERATURES WILL CONTINUE
OVER THE REGION THROUGH TUESDAY. CURRENT FORECASTS LOOK OK. NO
UPDATES PLANNED. PREVIOUS DISCUSSION BELOW WITH A FEW EDITS STILL
APPLY.

PORTIONS OF PREVIOUS DISCUSSION...
CONSIDERABLE AMOUNT OF HIGH LEVEL CLOUDS STREAMED ACROSS THE
SOUTHWEST DESERT REGION SUNDAY AFTERNOON...AS A SHORT WAVE MOVED
INLAND.

GREATEST WEATHER IMPACT THIS EVENING...OTHER THAN A FEW SPRINKLES...
APPEARS TO BE LOCALLY BREEZY CONDITIONS OVER PARTS OF SOUTHEAST
CALIFORNIA WITH THE PASSAGE OF A DISORGANIZED COLD FRONT.
DIMINISHING WIND IN SOUTHEAST CA...WHICH EARLIER PEAKED TO 32 MPH AT
IMPERIAL CA AND 24 MPH AT BLYTHE CA AT 01Z...IS EXPECTED TO DIMINISH
THE REMAINDER OF THE EVENING.

THE SHORTWAVE TROUGH AXIS WILL PASS THROUGH THE REGION MONDAY...AND
ALTHOUGH HEIGHTS ALOFT WILL CHANGE LITTLE...MODEL TRENDS ARE LEANING
TOWARDS STRONGER CAA WITHIN THE MIXED BOUNDARY LAYER. THIS TENDENCY
IS REFLECTED IN MODEL GUIDANCE TEMPERATURES SEVERAL DEGREES LOWER
THAN PREVIOUS ITERATIONS...AND HAVE FOLLOWED SUIT CUTTING JUST UNDER
THE MEDIAN OF ALL AVAILABLE GUIDANCE. RATHER TRANQUIL WEATHER WILL
FOLLOW INTO THE MIDWEEK PERIOD WITH SHORTWAVE RIDGING CHARACTERIZED
BY H5 HEIGHTS IN A 570-573DM RANGE SITUATED OVER THE AREA. USED A
GENERAL MODEL BLEND WITH RESPECT TO TEMPERATURES...AND DEPENDING ON
CLOUD COVER (OR LACK THEREOF) MAY NEED TO PUSH AFTERNOON HIGHS
SLIGHTLY WARMER BASED ON HISTORICAL TRENDS.

OPERATIONAL MODELS REMAIN VERY STEADY IN CONTINUITY...TIMING...AND
TRENDS TOWARDS A SIMILAR SOLUTION FORECASTING A MODERATE NEGATIVE
HEIGHT ANOMALY DIGGING INTO THE SWRN CONUS THOUGH THE END OF THE
WEEK. DESPITE THIS APPARENT SIGNAL OF HIGHER CONFIDENCE...SPREAD
AMONG ENSEMBLE MEMBERS (AND PARTICULARLY CMC MEMBERS) HAS ACTUALLY
GROWN IN THE PAST SEVERAL RUNS...KEEPING A LARGER AMOUNT OF
UNCERTAINTY IN THIS FORECAST PACKAGE. AND EVEN THE RELATIVELY MINOR
TIMING AND POSITIONAL DIFFERENCES BETWEEN OPERATIONAL MEMBERS...AS
THE CIRCULATION CENTER ATTEMPTS TO DISASSOCIATE WITH THE NORTHERN
STREAM STEERING FLOW...LIMITS MORE FORECAST SPECIFICS AT THIS TIME.
REGARDLESS...GIVEN THE PRESENCE OF A DEEPER SYSTEM ACROSS THE REGION
SOMETIME DURING THIS TIME FRAME...HAVE KEPT POPS SPREAD OVER THE ERN
CWA ABOVE CLIMATOLOGY...WHILE HEDGING TEMPERATURES MUCH BELOW
AVERAGE AND TOWARDS BIAS CORRECTED RAW MODEL OUTPUT (AND EVEN THESE
FORECASTS UP TO 10F BELOW NORMAL MAY NEED TO BE ADJUSTED DOWNWARD
DEPENDING IN THE EXACT TIMING AND TRACK OF THE COLD CORE ALOFT).

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA AND KSDL...

THROUGH 08Z MON...LIGHT WIND. BKN CLDS AOA 15 THSD AGL. 08Z MON
THROUGH 20Z MON...SCT CLDS AOA 16 THSD AGL. LIGHT WIND.

SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...

THROUGH 10Z MON...SCT CLOUDS AOA 15 THSD AGL. SOUTHWEST WIND 10 TO
15 KNOTS. FROM 10Z MON TO 20Z MON...SCT CLDS AOA 16 THSD AGL...
SOUTHWEST WIND 5 TO 10 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
RIDGING WILL QUICKLY RETURN TO THE AREA BY TUESDAY...WARMING DAYTIME
TEMPERATURES BACK ABOVE NORMAL HIGH AND GENERATING LIGHT WINDS FOR
TUESDAY AND WEDNESDAY. MINIMUM HUMIDITY PERCENTAGES SHOULD IN THE
MID TEENS FOR TUESDAY AND WEDNESDAY WITH GOOD TO EXCELLENT OVERNIGHT
RECOVERIES. BY WEDNESDAY...THE RIDGE BREAKS DOWN WHILE WINDS ALOFT
TURN SOUTHWESTERLY AS A LARGE AREA OF PACIFIC LOW PRESSURE BEGINS
EXPAND DOWN THE WEST COAST. THIS SYSTEM WILL TRACK FURTHER TO SOUTH
INTO OUR AREA AND IS BETTER ORGANIZED AS COMPARED TO THE WEAKER
SYSTEM EARLIER IN THE WEEK. SHOWER ACTIVITY...MUCH COOLER
TEMPERATURES AND INCREASING WINDS ARE POSSIBLE BY THE LATE WEEK AND
HEADING INTO NEXT WEEKEND.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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DISCUSSION...VASQUEZ/MEYERS/MO
AVIATION...VASQUEZ
FIRE WEATHER...NOLTE