Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 060956
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
256 AM MST WED MAY 6 2015

.SYNOPSIS...
DRIER AND BREEZY CONDITIONS WILL OCCUR THROUGH THURSDAY BEFORE A
STRONG EASTERN PACIFIC WEATHER SYSTEM MOVES INTO THE REGION BY
FRIDAY. THIS SYSTEM WILL BRING EVEN COOLER TEMPERATURES...CONTINUED
GUSTY WINDS...AND MORE PRECIPITATION CHANCES INTO SATURDAY. A SLOW
WARMING TREND COMMENCES THROUGH THE WEEKEND INTO EARLY NEXT WEEK AS
HIGH PRESSURE GRADUALLY REBUILDS OVER THE DESERT SOUTHWEST.

&&

.DISCUSSION...
DRY AIR IN THE LOW LEVELS WILL CONTINUE TO WORK INTO THE DESERT
SOUTHWEST TODAY. THIS WILL KEEP THINGS DRY ACROSS THE ENTIRE AREA
TODAY EVEN THOUGH A WEAK SHORTWAVE TROUGH WILL TRAVERSE THE REGION
THROUGH TONIGHT. CURRENT WATER VAPOR IMAGERY SHOWS THE VORTICITY MAX
JUST OFF THE SOUTHERN CALIFORNIA COAST WITH MODEST MID LEVEL MOISTURE
OUT AHEAD. THIS IS CAUSING A DECENT AMOUNT OF MID LEVEL CLOUDS
SPREADING EASTWARD ACROSS ARIZONA. THE SHORTWAVE TROUGH AND THE
CLOUDS WILL EXIT THE AREA BY LATE THIS EVENING BEFORE ANOTHER MORE
POTENT SYSTEM MOVES IN FOR FRIDAY. DAYTIME WINDS WILL BE QUITE BREEZY
TODAY AND THURSDAY UNDER A MODEST SURFACE PRESSURE GRADIENT. MAY SEE
SOME GUSTS IN THE 30-40 MPH RANGE ACROSS SOUTHEAST CALIFORNIA AND
20-30 MPH OVER SOUTH-CENTRAL ARIZONA. CAN/T RULE OUT THE POSSIBILITY
OF SOME BLOWING DUST...BUT AT THIS TIME FEEL IT WILL BE ISOLATED.

MODELS ARE IN EXCELLENT AGREEMENT WITH THE UPCOMING STRONG UPPER LOW
MOVING SOUTHWARD THROUGH CALIFORNIA ON THURSDAY AND INTO THE DESERT
SOUTHWEST ON FRIDAY. THIS WILL DEFINITELY BRING COOLER TEMPERATURES
INTO THE REGION...POTENTIALLY AS LOW AS 15 DEGREES BELOW NORMAL ON
FRIDAY...BUT THERE IS SOME DOUBT ON HOW MUCH MOISTURE WILL RETURN
AHEAD OF THE SYSTEM. UP TO THIS POINT MODELS HAVE BEEN SUGGESTING
THIS SYSTEM WILL BE MOSTLY DRY WITH LITTLE CHANCES FOR ANY RAIN...BUT
THE LATEST 00Z RUNS ARE STARTING TO SHOW SOME HIGHER MOISTURE LEVELS
AND FEEL THIS IS STILL PROBABLY TOO PESSIMISTIC. AM THINKING MOISTURE
LEVELS WILL ACTUALLY BE HIGHER THAN CURRENTLY DEPICTED...THUS OUR
RAIN CHANCES WILL BE BETTER AND THIS IS SHOWN ON THE LATEST SREF RUN.
HAVE INCREASED RAIN CHANCES ON FRIDAY AND SATURDAY...BUT WILL LIKELY
HAVE TO INCREASE THOSE FURTHER BEFORE THE EVENT OCCURS. STORM
DYNAMICS WILL BE FAIRLY ROBUST AS IT MOVES THROUGH CALIFORNIA...BUT
BY THE TIME THE UPPER LOW MOVES INTO THE DESERT SOUTHWEST IT WILL BE
FILLING AND FORCED ASCENT WILL BE WEAKENING.

UNSEASONABLY COOL AIR WILL MOVE IN WITH THE STORM SYSTEM WITH 850MB
TEMPERATURES DROPPING TO AROUND 12C ON FRIDAY. HAVE LOWERED OUR
FORECAST HIGHS ON FRIDAY FURTHER WITH LOWER DESERT HIGHS MAINLY ONLY
IN THE LOW TO MID 70S. THE UPPER LOW WILL STILL AFFECT ARIZONA INTO
EARLY SATURDAY WITH A TRAILING VORTICITY LOBE FORECAST TO SWING
THROUGH SOUTH-CENTRAL AND EASTERN ARIZONA BETWEEN 12-18Z. THIS WILL
LIKELY SPARK OFF ADDITIONAL SHOWERS AND POTENTIALLY SOME
THUNDERSTORMS UNDER STEEP MID LEVEL LAPSE RATES. AFTER 18Z
SATURDAY...SUBSIDENCE ALOFT WILL QUICKLY TAKE OVER FROM WEST TO EAST
WITH SKIES CLEARING AND ONLY A SLIGHT CHANCE OF SOME LINGERING
SHOWERS OVER OUR EASTERN HIGH TERRAIN AREAS.

SUNDAY INTO EARLY NEXT WEEK WILL TRANSITION BACK INTO MORE NORMAL
CONDITIONS WITH WEAK RIDGING ALOFT TAKING OVER AND TEMPERATURES
WARMING BACK TOWARD NORMAL STARTING NEXT MONDAY. WILL BE WATCHING
ANOTHER POTENTIAL STORM SYSTEM FOR THE MIDDLE OF NEXT WEEK DROPPING
OUT OF THE NORTHERN PACIFIC...BUT AT THIS TIME BOTH THE GFS AND
EUROPEAN KEEP IT WELL TO OUR NORTH.

&&

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

YESTERDAYS LOW PRESSURE SYSTEM NOW OVER THE PLAINS STATES.
AOME ALTOCUMULUS WILL LINGER BUT WITH SPOTTY COVERAGE. CIRRUS
INCREASES TONIGHT AHEAD OF A WEAK DISTURBANCE CENTERED JUST OFF THE
SOUTHERN CALIFORNIA COAST AS OF 04Z. EXPECT LIGHT SURFACE WINDS
OVERNIGHT AND INTO THE MORNING HOURS BEFORE SOUTH AND SOUTHWEST
WINDS DEVELOP WEDNESDAY AFTERNOON WITH SOME MODEST GUSTINESS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

THURSDAY THROUGH MONDAY...A SERIES OF PACIFIC WEATHER SYSTEMS WILL
MOVE INTO THE WESTERN STATES MAINLY NORTH OF SOUTHERN AZ THROUGH
SATURDAY...RESULTING IN BELOW NORMAL TEMPERATURES. PARTLY CLOUDY
SKIES ARE EXPECTED WITH BREEZY AFTERNOONS. HOWEVER THE STRONGEST
WIND PERIOD WILL BE THURSDAY AND FRIDAY WITH WINDS 15 TO 25 MPH AND
POSSIBLE GUSTS TO 30 MPH. A SLIGHT CHANCE OF SHOWERS IS POSSIBLE
FRIDAY AND SATURDAY AFTERNOONS MAINLY OVER SOUTHERN GILA COUNTY. A
HIGH PRESSURE SYSTEM WILL REBUILD OVER THE REGION LATE SUNDAY AND
MONDAY FOR CLEAR SKIES...LIGHT WIND...AND WARMER TEMPERATURES.
MINIMUM RELATIVE HUMIDITY IN GENERAL WILL RANGE FROM 15 TO 20
PERCENT...FALLING MONDAY INTO THE 10 TO 15 PERCENT RANGE. OVERNIGHT
RECOVERY WILL BE POOR TO FAIR.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&

$$

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

DISCUSSION...KUHLMAN
AVIATION...AJ
FIRE WEATHER...VASQUEZ


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