Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 162211
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
310 PM MST WED APR 16 2014

.UPDATE...AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...
DRY WESTERLY FLOW ALOFT WILL PERSIST THROUGH MUCH OF THE WORK WEEK
WITH HIGH TEMPERATURES WARMING INTO THE 90S OVER THE WARMER DESERTS.
A WEAK UPPER LEVEL LOW APPROACHING FROM THE EAST PACIFIC WILL SPREAD
INCREASING MOISTURE AND CLOUDS INTO THE AREA FRIDAY INTO THE
EARLY WEEKEND...LEADING TO A SLIGHT CHANCE OF SHOWERS ACROSS SOUTH
CENTRAL ARIZONA AND THE POSSIBILITY FOR SLIGHTLY COOLER DAYTIME
TEMPERATURES. THE COOL DOWN WILL BE SHORT LIVED...AS HIGH PRESSURE
QUICKLY RETURNS THROUGH THE LATE WEEKEND.

&&

.DISCUSSION...
EARLY AFTERNOON SATELLITE IMAGERY REVEALING A BAND OF CLOUDS MOVING
SE THROUGH CENTRAL AND NORTHERN ARIZONA...FROM A SHORTWAVE FEATURE
THAT IS SWEEPING THROUGH THE FOUR CORNERS AREA THIS AFTERNOON.
TEMPERATURES ARE RUNNING A HANDFUL OF DEGREES ABOVE TUESDAY...SO
THIS SHORTWAVE SHOULD HAVE NEARLY NO IMPACT TO OUR FORECAST ASIDE
FROM SOME BREEZES THIS EVENING. VERY SIMILAR DAY ON THURSDAY
EXPECTED...ABOVE NORMAL TEMPERATURES WITH MOSTLY CLEAR SKIES
EXPECTED.

THURSDAY THROUGH SATURDAY...AN ELONGATED PACIFIC TROUGH IS
FORECAST TO MOVE ONTO THE WEST COAST WITH THE LOW CIRCULATION
CENTERED OVER SOUTHERN CALIFORNIA. PRECIPITABLE WATER VALUES ARE
MUCH MORE IMPRESSIVE WITH THIS SYSTEM AS COMPARED TO A SIMILAR SETUP
A FEW WEEKS AGO...PW VALUES UPWARDS OF 0.5 TO 0.75 INCH. COMPARING
PREVIOUS OPERATIONAL MODEL RUNS HAS SHOWN A SLOWER PROGRESSION AND A
MORE NEGATIVELY TILTED TROUGH CENTER FORECAST FOR FRIDAY INTO
SATURDAY. STRONGER UPWARD VERTICAL MOTION THROUGH A DEEP COLUMN OF
MOISTURE SPREADING FROM WEST TO EAST WILL INCREASE SHOWER CHANCES
FRIDAY AFTERNOON THROUGH SATURDAY. A BROAD AREA OF STRONG DIFFLUENCE
IN 200-300 MB LAYER ASSOCIATED WITH THE LOW WILL BE THE UPWARD
MOVEMENT NEEDED FOR SHOWER AND POSSIBLE THUNDERSTORM INITIATION.
COOLER TEMPERATURES ALOFT WITH THE COLD CORE OF THE SYSTEM...500 MB
TEMPS COOLING TO -16C TO -18C...WILL SET UP AN INVERTED V-LIKE UPPER
AIR SOUNDING PATTER...WHICH TRANSLATES TO STRONGER DOWNBURST WIND
PROBABILITIES AND INCREASED INSTABILITY. MINOR ADJUSTMENTS MADE TO
THE POP GRIDS AND LITTLE TO NO CHANGE IN TEMPERATURE FORECAST WAS
MADE. WHILE CHANCES FOR SHOWERS LOOK MUCH BETTER WITH THIS SYSTEM
SIGNIFICANT RAINFALL IS NOT EXPECTED. DRY SUB-CLOUD LAYERS FROM HIGH
BASED STORMS MAY CREATE GUSTY WINDS AND STRONG OUTFLOWS. CHANCES FOR
BLOWING DUST MAY BE POSSIBLE AND SOMETHING TO CONSIDER WITH
FOLLOWING FORECAST PACKAGES.

&&

.PREVIOUS DISCUSSION.../ISSUED AT 317 AM MST 16 APRIL/...

NEXT WEEK...
MEDIUM RANGE OPERATIONAL AND ENSEMBLE MODEL FORECASTS ARE IN DECENT
AGREEMENT FOR THE EARLY PART OF NEXT WEEK`S FORECAST COMPARED TO
THEIR PERFORMANCE JUST 24 HOURS AGO. HIGH PRESSURE FROM OVER THE
WEEKEND WILL TRANSITION EASTWARD BEGINNING MONDAY...AS A LARGE AND
POTENT PACIFIC STORM MOVES INTO THE WEST COAST. IN GENERAL...LOWER
STORM HEIGHTS AND THE POTENTIAL FOR THE UPPER JET AS FAR SOUTH AS
ARIZONA COULD BRING SIGNIFICANT COOLING BY THE EARLY TO MIDDLE PART
OF NEXT WEEK (POTENTIALLY INTO THE LOW TO MID 80S ATTM). THE BULK OF
THE BEST WAVE ENERGY LOOKS REMAINS TO OUR NORTH...SO ONLY BLENDED A
FEW PERCENT OF CLIMO POPS INTO THE EXTENDED GRIDS FOR NOW.

&&

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

THROUGH 05Z THU...SCT HIGH CLDS AOA 25 THSD MSL. SOUTHWEST WIND 5 TO
15 KNOTS. FROM 05Z THU TO 18Z THU...SCT CLDS AOA 25 THSD MSL. LIGHT
VRBL WIND UNDER 7 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE..MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...DEWEY/NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ












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