Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 021646
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
946 AM MST THU JUL 2 2015

.SYNOPSIS...
ALTHOUGH HIGH MONSOON HUMIDITY WILL REMAIN OVER THE REGION...THE
ATMOSPHERE WILL BECOME A LITTLE MORE STABLE TODAY AND FRIDAY...FOR
REDUCED CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS. THE CHANCE
OF THUNDERSTORMS HOWEVER WILL INCREASE AGAIN THIS WEEKEND...WITH
MOST THUNDERSTORM CHANCES NEXT WEEK SHIFTING INTO EASTERN ARIZONA.

&&

.DISCUSSION...
QUIETER CONDITIONS WEATHER-WISE NOTED ACROSS THE FORECAST AREA AS
COMPARED TO THE LAST COUPLE MORNINGS...WITH CLEARING SKIES AND
SLOWLY RECEDING DEWPOINT READINGS. 12Z SFC/RAOB ANALYSIS INDICATE A
STILL DEEP AND NEAR EXCESSIVE LL MOISTURE SURFACE HOLDING OVER MUCH
OF AZ...WITH 850MB DEWPOINTS RANGING FROM TO 10 TO 15C AND PWATS
1.55 INCHES FOR BOTH PHOENIX AND TUCSON. HOWEVER...THIS MOISTURE
SURFACE HAS ALREADY BEGUN TO SLOWLY THIN AND DECREASE THIS AM...WITH
GPS IPW READINGS HEADING SOUTH OF 1.25 INCH READINGS ACROSS THE
WESTERN CWA AND THE INTL BORDER. SURFACE DEWPOINTS ARE ALSO UNDER
THEIR EXCESSIVE AND THE-SOUTHWESTS-VERSION-OF-MUGGY READINGS IN THE
MID 50S TO 60S THROUGHOUT THE LOWER DESERTS...3 TO 8 DEGREES DRIER
REGARDING 24 HR CHANGE.

SYNOPTICALLY...THE ML/UL RIDGE CIRCULATION CENTERS CONTINUE TO
TRANSITION THROUGH THE FOUR CORNERS/NM AREA TO OUR EAST. LITTLE
CHANGE ANTICIPATED REGARDING FLOW ALOFT MAINTAINING SOUTH-
SOUTHEASTERLY HEADING AND ADVECTING SLIGHTLY MORE STABLE AND WARMER
AIR INTO THE REGION FROM NORTHERN MEXICO. GLANCE THROUGH 06Z GFS/12Z
NAM BUFR SOUNDINGS INDICATE SUB-500 J/KG CAPE VALUES FOR PHOENIX-
BLYTHE-YUMA TODAY AND BETTER AMOUNTS OVER THE TYPICAL EASTERN HIGHER
TERRAIN/MOGOLLON RIM. HI-RES AND DETERMINISTIC QPF PLOTS KEEP
ACTIVITY OVER THE HIGHER TERRAIN...LENDING ITSELF TO SOUTHERN GILA
COUNTY STANDING THE BEST CHANCE TODAY FOR STORM ACTIVITY. UPDATES
THIS AM INCLUDED SCALING BACK POP CHANCES FOR THE DAYLIGHT HOURS
TODAY AND CLEARING OUT SKY GRIDS TO MATCH CURRENT TRENDS.

&&

.PREVIOUS DISCUSSION/ISSUED AT 325 AM MST/PDT/...

TODAY AND FRIDAY...
FLOW PATTERN ALOFT HAS CHANGED SOMEWHAT WITH PARAMETERS NOT FAVORING
ANY LARGE AFTERNOON AND EVENING CONVECTIVE OUTBREAKS OVER THE
FORECAST AREA...SOUTHEAST CA TO SOUTH CENTRAL AZ.

LAST EVENINGS UPPER AIR DATA SHOWED UNSEASONABLY WARM MID LEVEL
TEMPERATURES...IN THE MINUS 2 TO MINUS 4 RANGE AT 500 MB OVER
SOUTHERN NEW MEXICO/NORTH CENTRAL MEXICO. MODELS ADVECT THIS WARM
AIR INTO CENTRAL AZ TODAY AND FRIDAY WHICH SHOULD STABILIZE THE
AIRMASS SOMEWHAT. ALSO...300/250 MB HIGH CENTERS ARE FORECAST TO
GYRATE NEAR THE FOUR CORNERS REGION THIS PERIOD PROVIDING MOST UPPER
LEVEL CONVECTIVE SUPPORT TO DEVELOP ALONG THE MOGOLLON RIM...AND
OVER THE FAR WESTERN NEW MEXICO MOUNTAINS.

DATA ALSO SHOWED BOUNDARY LAYER MOISTURE WAS NEARLY EXCESSIVE OVER
PARTS OF SOUTHEAST CA...AND OVER THE SOUTHWEST QUARTER OF AZ. LOW
LEVEL WESTERLY WINDS TODAY SHOULD RECIRCULATE OR REDISTRIBUTE SOME
OF THIS MOISTURE BACK INTO SOUTH CENTRAL AZ...MEANING TOWARD
PHOENIX. THEREFORE...DUE TO AN UNUSUALLY HIGH AMOUNT OF BOUNDARY
LAYER MOISTURE...AND WARMER AFTERNOON SURFACE TEMPS TODAY...DESPITE
THE SLIGHTLY MORE STABLE ATMOSPHERE ALOFT...WE WILL CONTINUE TO
FORECAST LOW GRADE PRECIP PROBABILITIES ACROSS OUR REGION THE NEXT 2
DAYS. AN EXCEPTION WILL BE SOUTHERN GILA COUNTY WHERE OUTFLOWS FROM
MOGOLLON RIM/WHITE MOUNTAIN CONVECTION MAY INITIATE A BETTER CHANCE
OF AFTN STORMS.

SATURDAY AND SUNDAY...
MODELS FORECAST THE 300/250 MB HIGH CENTERS TO MOVE SOUTHWARD INTO
NORTH CENTRAL MEXICO...SOUTHWEST OF EL PASO THIS WEEKEND. THIS
PATTERN DEVELOPS A SOUTHERLY FLOW ALOFT WITH A NUMBER OF HARD TO
TIME MINOR DISTURBANCES MOVING INTO AZ. MID LEVEL TEMPERATURES AT
500 MB ALSO DECREASE INTO THE MINUS 6 DEG RANGE WHICH IS NORMAL FOR
THE SEASON. WITH WARMER SURFACE TEMPS AND MORE FAVORABLE SUPPORT
ALOFT FORECAST THIS WEEKEND...PROBABILITY OF PRECIP WILL BE RAISE A
BIT ACROSS MUCH OF SOUTHWEST AND SOUTH CENTRAL AZ.

MONDAY THROUGH WEDNESDAY...
MODELS FORECAST MID/UPPER LEVEL FLOW TO BECOME MORE WESTERLY THIS
PERIOD...WITH ONLY ONE PERTURBATION FORECAST TO MOVE INTO AZ ABOUT
TUESDAY. AS A RESULT...MOST OF THE BOUNDARY LAYER MOISTURE IN AZ
GETS PUSHED INTO THE EASTERN HALF OF THE STATE. THEREFORE THE
CONVECTIVE POTENTIAL WILL FAVOR THE MOUNTAINS NORTH THROUGH EAST OF
PHOENIX. MID LEVEL STEERING CURRENTS ALSO BECOME WESTERLY. THEREFORE
A ONLY A SLIGHT CHANCE OF LATE AFTERNOON/EVENING STORMS ARE FORECAST
ON THE SOUTH CENTRAL DESERTS...WITH SLIGHTLY HIGHER PROBABILITIES IN
OUR MOUNTAINOUS ZONE 24 EAST OF PHOENIX.

THURSDAY AND FRIDAY...
FLOW ALOFT THIS PERIOD WILL BECOME MORE MONSOONISH AS MID/UPPER
LEVEL WINDS BECOME MORE SOUTH TO SOUTHEASTERLY. MODELS ALSO FORECAST
A DEEPER EASTERLY FLOW TO DEVELOP JUST SOUTH OF THE BORDER WITH A
COUPLE OF HARD TO TIME INVERTED TROFS BRUSHING THE MEXICAN BORDER.
THEREFORE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS WILL BE PUT
BACK INTO THE FORECAST ACROSS A LARGE PORTION OF SOUTHWEST AND SOUTH
CENTRAL AZ THIS PERIOD.


&&

.AVIATION...

SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...
HIGH PRESSURE ALOFT AND A SOMEWHAT DRIER AIRMASS IS EXPECTED TO
THUNDERSTORM ACTIVITY WELL EAST OF THE TERMINALS TODAY...WITH LITTLE
CHANCE OF EVEN OUTFLOWS FROM THESE STORMS AFFECTING THE TERMINALS.
HIGH CIRRUS CIGS TO REMAIN THE RULE THROUGH THE TAF PERIOD...WITH
JUST A FEW MID-LEVEL CLOUDS PASSING OVER THE TERMINALS FOR A TIME
DURING THE LATE AFTERNOON AND EVENING HOURS. WINDS TO REMAIN MAINLY
FROM A WESTERLY DIRECTION THROUGH THE TAF PERIOD...WITH SUSTAINED
WIND SPEEDS AS HIGH AS 15KTS...AND GUSTS AS HIGH AS 25KTS POSSIBLE
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
MAINLY CLEAR SKIES...WITH JUST SOME FEW-SCT CIRRUS LAYERS PASSING
OVERHEAD FROM TIME-TO-TIME THROUGH THE TAF PERIOD. WINDS TO MAINLY
FOLLOW TYPICAL DIURNAL TRENDS AT KIPL...AND TO REMAIN MAINLY OUT OF
A SOUTHERLY DIRECTION AT KBLH...WITH SOME AFTERNOON BREEZINESS
POSSIBLE AT KBLH AS WELL.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
A LOW GRADE MONSOON PATTERN WILL REMAIN IN PLACE ACROSS THE AREA
SATURDAY WITH BASICALLY SLIGHT CHANCES FOR SHOWERS OR THUNDERSTORMS
FROM PHOENIX EASTWARD. TEMPERATURES SATURDAY WILL HOVER NEAR
SEASONAL NORMALS WITH MINIMUM RH VALUES RANGING FROM UPPER TEENS TO
MID 20S. A MORE SOUTHERLY FLOW ALOFT WILL ALLOW INCREASING MOISTURE
TO SPREAD INTO THE AREA ON SUNDAY INTO MONDAY FOR AN INCREASING
CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS. HIGH TEMPERATURES
WILL FALL BELOW NORMAL VALUES AND HUMIDITIES WILL RISE INTO THE 20
TO 30 PERCENT BALLPARK. BY EARLY NEXT WEEK...AN AREA OF LOW PRESSURE
APPROACHING THE CALIFORNIA COAST WILL SHIFT FLOW ALOFT MORE TOWARDS
THE SOUTHWEST...BRINGING SOMEWHAT DRIER AIR INTO THE WESTERN
DESERTS. THIS WILL TEND TO CONFINE SHOWERS AND THUNDERSTORMS TO THE
CENTRAL DESERTS AND AREAS EASTWARD. ALSO...HIGH TEMPERATURES WILL
CLIMB BACK TO NEAR OR SLIGHTLY ABOVE NORMAL LEVELS WITH THE HOTTER
WESTERN DESERTS APPROACHING 110 DEGREES. GUSTY SOUTH TO SOUTHWEST
WINDS ARE EXPECTED ACROSS THE DESERTS OVER THE WEEKEND WITH PEAK
GUSTS IN EXCESS OF 25 MPH AT TIMES. SLIGHTLY LESS WIND IS EXPECTED
AS WE MOVE INTO NEXT WEEK...WITH JUST TYPICAL SOUTHWEST TO WEST
GUSTINESS IN THE AFTERNOON.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS
ACCORDING TO STANDARD OPERATING PROCEDURES.

&&

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

&&

$$

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

DISCUSSION...NOLTE
PREVIOUS DISCUSSION...VASQUEZ
AVIATION...PERCHA
FIRE WEATHER...PERCHA



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