Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 012117
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
215 PM MST FRI AUG 01 2014

.SYNOPSIS...
STORM CHANCES RESUME LATER THIS AFTERNOON AND EVENING WITH THE BEST
CHANCES OVER THE HIGHER TERRAIN AND SOUTHWEST ARIZONA. ACTIVE
MONSOON CONDITIONS ARE ANTICIPATED THIS WEEKEND ACROSS THE REGION AS
AN UPPER LOW SLOWLY MOVES ACROSS ARIZONA AND SOUTHEAST CALIFORNIA.
NEXT WEEK...A DOWNTREND IN THUNDERSTORM CHANCES TAKES PLACE ALONG
WITH A WARMING TREND AS DRIER AIR FILTERS IN FROM THE WEST.

&&

.DISCUSSION...
UPPER HIGH CENTER HAS SHIFTED INTO FAR WCNTRL AZ...AND FLOW BETWEEN
THE HIGH AND AN UPPER LOW SOUTH OF ARIZONA HAS BECOME EASTERLY. THIS
FAVORABLE EASTERLY FLOW HAS BEEN IMPORTING INCREASING MOISTURE INTO
THE LOWER AZ DESERTS...AND PWAT VALUES HAVE CLIMBED TO AROUND 1.7
INCHES ACROSS SRN AZ. SURFACE DEWPOINTS OVER THE LOWER DESERTS ARE
ALSO UP SIGNIFICANTLY...AT 2 PM MOST VALUES WERE IN THE LOW TO MID
60S AND THOSE NUMBERS ARE 7 TO 11 DEGREES HIGHER THAN 24 HOURS AGO.
LATEST RADAR INDICATED THAT THE MORNING SHOWERS/STORMS ACROSS
WESTERN MARICOPA COUNTY HAVE PRETTY MUCH ENDED AND THERE WAS VERY
LITTLE ON THE SCOPE CONVECTIVELY SPEAKING...OVER THE AZ DESERTS OR
EVEN THE HIGHER TERRAIN OF SERN AZ. THE LACK OF CONVECTION SO FAR
THIS AFTERNOON IS LARGELY A RESULT OF THE THICK MID/HIGH CLOUD COVER
THAT HAS PERSISTED INTO THE AFTERNOON HOURS...AND THAT HAS HELD
TEMPS DOWN AND IN THE 90S. TEMPS IN THE CENTRAL DESERTS WERE RUNNING
10-15 DEGREES COOLER THAN 24 HOURS AGO...AND THIS HAS REALLY
DIMINISHED CAPE/INSTABILITY IN THE ATMOSPHERE. GIVEN THE HIGH
MOISTURE VALUES AND BETTER EASTERLY STEERING FLOW...WILL CONTINUE TO
FORECAST 20-30 PERCENT CHANCES FOR STORMS THIS EVENING...MAINLY EAST
OF THE LOWER CO RIVER VALLEY...ALTHOUGH THOSE NUMBERS MAY BE A BIT
ON THE HIGH SIDE.

AFTER MIDNIGHT...AS AN INVERTED TROF STARTS TO ROTATE AROUND THE
UPPER HIGH AND INTO SERN AZ...MOISTURE WILL CONTINUE TO INCREASE
ACROSS SOUTH CENTRAL AZ AND AS SUCH WE WILL RAISE POPS TO AROUND 20
PERCENT...CALLING FOR ISOLATED SHOWERS/STORMS TO DEVELOP AND MOVE
INTO THE GREATER PHOENIX AREA UNDER MOSTLY CLOUDY SKIES.

SATURDAY AND SUNDAY...
MODEL GUIDANCE IS VERY CONSISTENT IN CALLING FOR A SIGNIFICANT
UPRAMP IN MOISTURE COMBINED WITH STRONGER DYNAMICS IN THE FORM OF AN
INVERTED TROF WHICH WILL ROTATE AROUND THE UPPER HIGH AND MOVE INTO
THE CENTRAL AND WESTERN AZ DESERTS ON SATURDAY/SAT NIGHT. AS THIS
OCCURS...PWAT VALUES CLIMB TO NEAR 2 INCHES OVER PORTIONS OF THE
DESERTS...AND WIND FIELDS STRENGTHEN FROM THE SOUTH OR SOUTHEAST.
DIFLUENCE ALOFT ALSO INCREASES. WE WILL SEE SCATTERED TO NUMEROUS
SHOWERS DEVELOP FROM THE SOUTHEAST SATURDAY UNDER MOSTLY CLOUDY
SKIES...AND THERE WILL BE EMBEDDED THUNDERSTORMS. GIVEN THE HIGH
MOISTURE CONTENT AND EXPECTED WELL BELOW NORMAL HIGH
TEMPERATURES...CAPE/INSTABILITY WILL BE DIMINISHED AND AS SUCH THE
WEATHER PROBLEMS WILL REVOLVE AROUND HYDRO ISSUES MORE THAN SEVERE
STORMS WITH STRONG GUSTY OUTFLOW WINDS. BEST WEATHER WINDOW LIKELY
TO BE SAT AFTERNOON THROUGH THE EVENING HOURS...AND WE MAY SEE
ENOUGH HEAVY RAIN TO RESULT IN SMALL STREAM FLOOD ADVISORIES AS WELL
AS AREAL FLOODING OF LOW LYING AREAS...STREAMS AND WASHES. POP
TRENDS LOOK GOOD...THO WE DID RAISE VALUES 5-10 PERCENT ACROSS MUCH
OF THE AREA DURING THE LATE TONIGHT THRU SAT NIGHT PERIOD. HIGH
TEMPS WERE ALSO LOWERED SEVERAL DEGREES ON SATURDAY...ESPECIALLY
ACROSS SOUTH CENTRAL AZ...WHERE HIGHS WILL STRUGGLE TO CLIMB OUT OF
THE 90S. AS THE INVERTED TROF MOVES NORTH INTO SRN NEVADA/SERN CA
AND NWRN AZ ON SUNDAY...WE WILL SEE SHOWERS/STORMS START TO DECREASE
FROM THE SOUTH BUT POPS WILL STAY IN THE 20-30 PERCENT BALLPARK MOST
LOCATIONS.

MONDAY...
AS THE INVERTED TROF/DISTURBANCE RACES OFF WELL TO OUR NORTH...A
SOUTHWESTERLY FLOW ALOFT STARTS TO AFFECT THE LOWER SERN CA AND SRN
AZ DESERTS. DESPITE THE UNFAVORABLE STEERING FLOW...THERE WILL BE
SUFFICIENT LINGERING LOWER LEVEL MOISTURE TO ALLOW FOR ISOLATED
THUNDERSTORMS TO DEVELOP MAINLY DURING THE AFTERNOON AND EARLY
EVENING HOURS...FAVORING HIGHER TERRAIN AREAS TO THE NORTH AND EAST
OF PHOENIX. HIGH TEMPS MONDAY WILL CLIMB A FEW DEGREES AS THE
AIRMASS DRIES A BIT AND SUNSHINE INCREASES.

TUESDAY THROUGH FRIDAY...
THE FIRST HALF OF THE NEXT WORKWEEK CONTINUES TO LOOK LIKE A
DOWNTREND IN STORM ACTIVITY AS THE INVERTED TROUGH DEPARTS AND DRIER
AIR MOVES INTO THE REGION AND GETS REINFORCED BY A BROADER TROUGH IN
THE WESTERLIES. ACCORDINGLY POPS RETREAT EASTWARD AND TEMPS SLOWLY
CLIMB...DROPPED POPS ALTOGETHER THURSDAY. LITTLE CHANGE EXPECTED ON
FRIDAY...ALTHOUGH MOISTURE INCREASES SLIGHTLY EAST OF PHOENIX
ALLOWING FOR A SLIGHT CHANCE OF AFTERNOON STORMS.

&&

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

CONSIDERABLE MID AND HIGH CLOUDS THAT ARE LEFT OVER FROM LAS NIGHT/S
TS ACTIVITY WILL CONTINUE TO SLOWLY THIN/CLEAR OUT THROUGH THE REST
OF THE AFTERNOON AND EARLY EVENING BEFORE THE NEXT ROUND OF TS
DEVELOPMENT BRINGS MORE CLOUDS AND AN OUTSIDE CHANCE FOR RAIN/GUSTY
WINDS FROM THE NORTHEAST LATER THIS EVENING. A MUCH BETTER CHANCE
FOR SHOWERS/STORMS IS ON TAP LATE TONIGHT AND SATURDAY AS A WEAK
WEATHER DISTURBANCE MOVING IN FROM THE SOUTH HELPS TO TRIGGER MORE
WIDESPREAD CONVECTIVE ACTIVITY OVER THE REGION. THERE WILL LIKELY BE
ENOUGH SHOWER/TS ACTIVITY TO PUSH CIGS DOWN AS LOW AS 5K FEET...OR
EVEN LOWER AT ONE OR MORE OF THE PHX TAF SITES BY EARLY SAT. WINDS
ARE EXPECTED TO MAINLY FOLLOW TYPICAL DIURNAL TRENDS...OUTSIDE OF
THUNDERSTORMS...WHICH COULD BRING RAPIDLY CHANGING WIND DIRECTIONS
AND THE POTENTIAL FOR STRONG GUSTS.

SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA......KIPL...AND KBLH...
PERSISTENT SOUTH TO SOUTHEASTERLY WINDS ARE EXPECTED THROUGH MUCH OF
THE TAF PERIOD...WITH INCREASING MID TO HIGH=LEVEL CLOUDINESS.
SHOWERS AND THUNDERSTORMS WILL BEGIN  TO MOVE INTO SE CA DURING THE
DAY ON SAT...WHICH COULD AFFECT EITHER...OR BOTH OF THE TERMINALS.
THESE STORMS WILL BRING THE POTENTIAL FOR SHIFTING WIND DIRECTIONS
AND STRONG GUSTS...ALONG WITH BRIEF HEAVY DOWNPOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
INCREASED MOISTURE WILL BE WIDESPREAD THROUGH EARLY NEXT WEEK WITH
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED SUNDAY
THROUGH TUESDAY WITH A DECENT CHANCE OF A WETTING RAIN EVEN ACROSS
SOME DESERT LOCATIONS. MINIMUM HUMIDITY VALUES WILL BE IN THE 20 TO
30 PERCENT RANGE THROUGH MONDAY AND THEN SLOWLY DECREASE GOING INTO
MID WEEK AS DRIER AIR WORKS IN FROM THE WEST. HIGH TEMPERATURES WILL
START OFF COOLER THEN NORMAL...WARMING UP TO NEAR NORMAL BY TUESDAY
AND THEN ABOVE NORMAL THROUGH THE END OF NEXT WEEK.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB/AJ
AVIATION...PERCHA
FIRE WEATHER...KUHLMAN















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