Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 051624
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
922 AM MST TUE MAY 5 2015

.SYNOPSIS...EXPECT SHOWERS TO DIMINISH AND SKIES BEGIN TO CLEAR
TODAY AS THE LOW PRESSURE SYSTEM MOVES TO THE EAST. A STRONGER
EASTERN PACIFIC WEATHER SYSTEM WILL MOVE INTO THE REGION BY
FRIDAY...BRINGING EVEN COOLER TEMPERATURES...GUSTY WINDS...AND MORE
PRECIPITATION CHANCES. A SLOW WARMING TREND COMMENCES THROUGH THE
WEEKEND INTO EARLY NEXT WEEK AS HIGH PRESSURE GRADUALLY REBUILDS
OVER THE DESERT SOUTHWEST.

&&

.DISCUSSION... REGIONAL UPPER AIR PLOTS AND SATELLITE IMAGERY REVEAL
THE UPPER LEVEL LOW MOVING EAST THIS MORNING...THE AXIS OF THE LOW
GENERALLY CENTERED ALONG THE AZ/NM BORDER...WITH WEAK RIDGING AND
AND INCREASING HEIGHTS OVER SOUTHEAST CALIFORNIA AND THE LOWER
COLORADO RIVER VALLEY. MODELS INDICATE THAT ANY RESIDUAL SHOWER
ACTIVITY WILL END BY MIDDAY OVER THE LOWER DESERTS OF SOUTH-CENTRAL
AZ...POSSIBLY SOME ISOLATED SHOWERS LINGERING INTO THE EARLY EVENING
HOURS OVER THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX. AFTERNOON
TEMPS ACROSS OUR CWA WILL GENERALLY WARM INTO THE UPPER 80S...THE
MORE PRONOUNCED WARMING EXPECTED OVER OUR WESTERN ZONES...ALL DUE TO
CLEARING SKIES AND BETTER INSOLATION. SHORT TERM DIGITAL FORECAST
GRIDS CAPTURE THE OBSERVED/MODEL TRENDS WELL...NO UPDATES PLANNED AT
THIS TIME.

WEDNESDAY...DRY CONDITIONS AND A BIT MORE WARMING (OVER SOUTH-
CENTRAL AZ) IS EXPECTED ON WEDNESDAY AS WEAK RIDGING PASSES OVER THE
REGION AHEAD OF THE NEXT UPPER LOW CENTER APPROACHING FROM THE WEST.
HOWEVER...HIGH TEMPERATURES ARE STILL EXPECTED TO REMAIN SLIGHTLY
BELOW NORMAL VALUES. SOME INCREASE IN AFTERNOON WESTERLY WINDS CAN
BE EXPECTED OVER SE CA AS WINDS ALOFT INCREASE AHEAD OF THE NEXT
SYSTEM.

THURSDAY THROUGH SATURDAY...ALTHOUGH LATEST MODEL SUITES ARE
CONSISTENT WITH EARLY RUNS ON THE BASIC IDEA THAT ANOTHER UPPER LOW
CENTER WILL AFFECT OUR REGION DURING THIS PERIOD...SOME DIFFERENCES
BETWEEN THE MODEL SUITES HAVE EMERGED ON THE TRACK OF THIS SYSTEM.
WHILE THE EURO AND GEM MODELS CONTINUE TO TAKE THIS LOW CENTER TO
OUR NORTH...ALONG THE AZ/UT BORDER...THE GFS NOW MOVES THE UPPER LOW
CENTER RIGHT ACROSS OUR CWA. IF THE GFS WERE TO VERIFY...EVEN COOLER
TEMPERATURES WOULD RESULT...WITH MANY LOWER DESERT LOCATIONS SEEING
HIGH ONLY IN THE 70S ON FRIDAY AND SATURDAY...ALONG WITH A CHANCE
FOR SHOWERS AS WELL. ALTHOUGH ALL THREE MODELS STILL INCREASE SFC
WINDS ACROSS THE REGION DURING THIS PERIOD...THEY ALL NOW KEEP
MINIMUM RH/S ELEVATED A BIT...MOSTLY IN THE UPPER TEENS AND
20S...WHICH WOULD KEEP FIRE DANGER LEVELS FROM RISING AS MUCH AS HAD
BEEN EARLIER EXPECTED. I HAVE DECIDED THE RAISE POPS AND COOL
TEMPERATURES A BIT TO REFLECT THIS POSSIBLE GFS SOLUTION.

SUNDAY THROUGH TUESDAY..ALL THREE GLOBAL MODELS CONTINUE TO SHOW
HIGH PRESSURE SLOWLY REBUILDING OVER THE REGION AS THE AFOREMENTIONED
UPPER LOW MOVES OFF TO THE EAST...WITH DRY CONTINUES AND A GRADUAL
WARMING TREND FORECAST THROUGH THIS PERIOD.

&&

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

AS AN AREA OF LOW PRESSURE SLUGGISHLY MOVES OFF TO THE NORTHEAST
TODAY...THERE WILL BE A LINGERING CHANCE OF MAINLY SHOWERS OVER THE
CENTRAL DESERTS...WITH WIDESPREAD CIGS BETWEEN 8K AND 12K FEET. BY
AFTERNOON A DRYING TREND WILL TAKE PLACE FROM THE SOUTHWEST...AND
CLOUD DECKS WILL SCATTER OUT...WITH FEW-SCT CU/SC MAINLY AOA 6K FEET
AFFECTING THE TERMINALS. BY MID AFTERNOON MOST PRECIP SHOULD BE
CONFINED TO HIGHER TERRAIN AREAS NORTH AND EAST OF PHOENIX. CANNOT
RULE OUT AN AFTERNOON SHOWER OR STORM IN THE GREATER PHOENIX AREA
BUT CONFIDENCE IS TOO LOW TO MENTION PRECIP IN THE TAFS.

NO STRONG WINDS EXPECTED NEXT 24 HOURS...WINDS SHOULD BE LARGELY
DIURNAL WITH EAST/SOUTHEAST MORNING WINDS TURNING BACK TO THE
SOUTHWEST AFTER 20Z OR SO.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

NO PRECIP EXPECTED FROM THE LOWER CO RIVER WESTWARD NEXT 24 HOURS AS
THE UPPER LOW MOVES OFF TO THE EAST. WINDS TO FAVOR THE SOUTH AT
BOTH KIPL AND KBLH...BECOMING LOCALLY GUSTY AT KBLH IN THE
AFTERNOON. WINDS TO INCREASE FROM THE WEST AFTER 5 PM AT KIPL.
EXPECT VARIABLE AMOUNTS OF CIRRUS AT THE TERMINALS NEXT 24 HOURS
WITH MAYBE A FEW MID CLOUD DECKS AS WELL AT KBLH.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
GUSTY WINDS WITH A COOLING TREND TO PREVAIL ACROSS THE REGION FROM
THURSDAY ONWARD INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES
ACROSS THE GREAT BASIN. FRIDAY WILL LIKELY BE THE COOLEST DAY WITH
HIGH TEMPERATURES ACROSS THE LOWER DESERTS FALLING INTO THE UPPER
70S TO LOWER 80S. IN GENERAL DRY CONDITIONS SHOULD PREVAIL DURING
THE PASSAGE OF THE LOW...BUT RECENT MODELS HAVE SUGGESTED THAT THERE
MAY BE A THREAT OF SHOWERS OR AFTERNOON THUNDERSTORMS FRIDAY INTO
SATURDAY. PRIMARILY DUE TO THE GUSTY AFTERNOON WINDS...FIRE DANGER
LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD AS AFTERNOON
HUMIDITIES FALL INTO THE TEENS...ESPECIALLY ACROSS SOUTHWEST AND
SOUTH CENTRAL ARIZONA. A WARMING AND DRYING TREND WILL TAKE PLACE
SUNDAY INTO MONDAY...AND THERE WILL BE LESS WIND AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST
AND HIGHER PRESSURE ALOFT BUILDS INTO THE AREA FROM THE WEST.

&&

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

$$

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

DISCUSSION...MEYERS/PERCHA
AVIATION...CB
FIRE WEATHER...CB


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