Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 031733 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
1033 AM MST FRI JUL 3 2015

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...
RELATIVELY HIGH MONSOON HUMIDITY AND A SLIGHTLY STABLE ATMOSPHERE
WILL KEEP THE CHANCE OF SHOWERS AND THUNDERSTORMS OVER SOUTH CENTRAL
ARIZONA TODAY...GENERALLY FROM PHOENIX EASTWARD. THE THREAT FOR
SHOWERS THIS WEEKEND WILL EXPAND INTO PARTS SOUTHWEST ARIZONA DURING
THE AFTERNOON AND EVENINGS. BY NEXT WEEK...DRIER WESTERLY FLOW WILL
PUSH MOST OF THE MONSOON MOISTURE INTO EASTERN ARIZONA WHERE THE
THREAT OF THUNDERSTORMS WILL CONTINUE.

&&

.DISCUSSION...
STORM CLOUD TOPS HAVE GRADUALLY BEGUN TO WARM THIS AM AFTER AN
EVENING OF LATE-STARTING AND PERSISTENT OVERNIGHT THUNDERSHOWER
ACTIVITY FOR THE SOUTHERN HALF OF AZ....ESPECIALLY OVER THE SOUTH-
CENTRAL DESERT AND POPULATION AREAS OF MARICOPA...PHOENIX... AND
WICKENBURG. MOST OF THE RADAR ACTIVITY HAS CLEARED THE PHOENIX
METRO...WITH TRAILING SHOWERS OVER NW MARICOPA COUNTY BEHIND A LINE
OF THUNDERSTORMS ACROSS LA PAZ AND MOHAVE COUNTY. ADDITIONAL
THUNDERSHOWERS UPSTREAM ARE STARTING TO NOSE INTO SOUTHERN GILA
COUNTY AND HEAD TOWARDS GLOBE THIS HOUR. UL SPEED MAX THE MAJORITY
OF THE HI-RES AND DETERMINISTIC MODELS UNDERDID YESTERDAY WITH THEIR
FORECASTS MANAGED TO ADVECT SOME DEEPER MOISTURE INTO THE REGION
FROM SONORA...WHERE A NEAR 2 INCH POCKET OF PWATS WAS OBSERVED ON
BLENDED TPW IMAGERY OVERNIGHT. IT ALSO SERVED TO PROVIDE SOME UL
DYNAMICS TO FLAIR UP THE STORM ACTIVITY. 12Z RAOB ANALYSIS ALSO
INDICATES A WEAK INVERTED WAVE ACROSS SOUTHERN AZ AND LITTLE
MODIFICATION TO TEMPERATURES ALOFT...WHICH WERE ADVERTISED TO BE
SLIGHTLY WARMER AT -2 TO -4C YESTERDAY AFTN AND DOWN TO -5
OVERNIGHT...THEY CAME IN THIS AM OBSERVED AT -6 TO -7C.

INITIAL UPDATES THIS AM WILL WORK IN ADDITIONAL THUNDERSHOWER
COVERAGE AND WORDING FURTHER WEST TOWARDS PARKER AND LA PAZ COUNTY
FOR THE REST OF THIS AM WHILE MAKING SIGNIFICANT ADJUSTMENTS TO
TODAY HIGH TEMPERATURES. WITH A STILL RICH MOISTURE PROFILE ALOFT
AND ELEVATED SFC DEWPOINTS...DAYTIME HIGHS 105-108F SEEM SOMEWHAT OF
A STRETCH ACROSS SOUTH-CENTRAL AZ. TEMPERATURES LOOK FAIRLY ON
TARGET FOR THE WESTERN AREAS OF THE FORECAST AREA AS DEBRIS
CLOUDINESS SHOULD LARGELY MISS THE MAIN POPULATION AREAS AND THEY
ARE ALREADY ON THEIR WAY INTO THE 90S AND ON PAR WITH READINGS FROM
THIS TIME YESTERDAY. EVEN THOUGH SLIGHTLY MORE STABLE CONDITIONS
SHOULD BE EXPECTED TODAY WITH THE AREA GENERALLY BE WORKED OVER WITH
LAST NIGHT`S STORM ACTIVITY...WILL LIKELY MAINTAIN CHANCE TO SLIGHT
CHANCE WORDING IN THE POP GRIDS FOR THIS AFTN/EVENING.

&&

.PREVIOUS DISCUSSION /ISSUED AT 117 AM MST/PDT/...
THIS SATURDAY AND SUNDAY...
MODELS FORECAST THE 300/250 MB HIGH CENTERS TO MOVE SOUTHWARD FROM
FAR NORTHEAST AZ FRIDAY MORNING...TO THE VICINITY OF EL PASO THIS
WEEKEND. THIS PATTERN VEERS THE BELT OF UNUSUALLY STRONG 300/250 MB
40-50 KNOT SOUTHEASTERLY WINDS...TO SOUTHERLY WINDS CENTERED ALONG
THE COLORADO RIVER VALLEY. A FEW HARD TO TIME DISTURBANCES...AS WELL
AS PERIODS OF DIVERGENT FLOW ALOFT DEVELOPS ACROSS SOUTHWEST AND
SOUTH CENTRAL AZ. THIS PORTENDS A THREAT OF AFTN/EVE SHWRS AND TSTMS
SAT AND SUN.

MONDAY THROUGH FRIDAY...
LATEST GFS MODEL FORECASTS HAVE CHANGED SINCE YDA...AND NOW
FORECASTS THE MID/UPPER LEVEL FLOW TO BECOME MORE WESTERLY THRU
FRIDAY. ONLY ONE PERTURBATION IS FORECAST TO MOVE INTO AZ ABOUT
TUESDAY. AS A RESULT...MOST OF THE BOUNDARY LAYER MOISTURE 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.

NEXT SATURDAY...
MODELS FORECAST AN INVERTED TROF IN THE EASTERLIES TO ROTATE OUT OF
WEST TEXAS THURSDAY NIGHT...AND INTO SOUTHERN AZ FRIDAY NIGHT OR
SATURDAY MORNING. NOT MUCH CREDENCE IS PUT INTO THE EXTENDED MODEL
FORECASTS DURING THE MONSOON...THEREFORE WE WILL CONTINUE WITH THE
LOW GRADE MONSOON THREAT OF AFTN/EVE SHWRS AND TSTMS OVER
PINAL...EASTERN MARICOPA...AND SOUTHERN GILA COUNTIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...
THE HEAVIEST SHOWERS HAVE LONG SINCE DISSIPATED BUT RADAR IS SHOWING
A FEW ISOLATED CELLS MOVING INTO THE SOUTHEAST VALLEY AS OF 1730Z.
NOT EXPECTING MUCH MORE THAN A SPRINKLE OR BRIEF SHOWER THROUGH
EARLY AFTERNOON. COVERAGE SHOULD BE SPARSE ENOUGH TO EXCLUDE ANY
MENTION IN THE PHOENIX TAFS. WINDS WILL FAVOR TYPICAL DIURNAL TRENDS.

CONDITIONS COULD TURN INTERESTING AGAIN LATE TONIGHT AS SOME OF THE
BETTER PERFORMING HI-RES GUIDANCE IS SUGGESTING ANOTHER ROUND OF
NOCTURNAL CONVECTION MOVING IN FROM THE EAST. MODEL SOLUTIONS ARE ALL
OVER THE PLACE TODAY BUT ENOUGH ARE SUGGESTING THIS POSSIBILITY THAT
I MENTIONED VCSH IN THE PHOENIX TERMINALS AFTER MIDNIGHT TONIGHT.
UNFORTUNATELY...LOW CONFIDENCE FORECAST FROM MID EVENING ONWARD.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOME OF THE ABOVE MENTIONED NOCTURNAL CONVECTION COULD SPREAD AS FAR
WEST AS BLH AND I ALSO INCLUDED A VCSH MENTION AFTER 09Z. NEARLY ALL
GUIDANCE KEEPS IPL DRY ALTHOUGH THEY WILL ALMOST CERTAINLY SEE
INCREASED CLOUD COVER OVERNIGHT AS STORMS DEVELOP/DISSIPATE OVER
MEXICO.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
TYPICAL MONSOON WEATHER EXPECTED ON SUNDAY...FOLLOWED BY DRYING AND
A RE-ORIENTING OF HIGHEST STORMS CHANCES WELL NORTH/EAST OF PHOENIX
MONDAY THROUGH MID WEEK. THIS WILL RESULT IN AFTERNOON HUMIDITIES IN
THE 10-20 PERCENT RANGE WITH FAIR/GOOD OVERNIGHT RECOVERIES
EXPECTED. WINDS WILL FAVOR TYPICAL DIURNAL UPSLOPE/DOWNVALLEY TRENDS
NEXT WEEK OUTSIDE OF THUNDERSTORM INDUCED OUTFLOWS.

&&

.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/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...LEINS


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