Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 230508
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1010 PM MST TUE JUL 22 2014


.SYNOPSIS...
A STRONG HIGH PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE REGION
THIS WEEK...RESULTING IN VERY HOT TEMPERATURES WEDNESDAY THROUGH
FRIDAY. AT SAME TIME...MONSOON MOISTURE WILL SLOWLY INCREASE OVER
THE AREA...WITH OCCASIONAL CLOUDINESS AT TIMES. INCREASED
MOISTURE...COMBINED WITH SEVERAL WEAK WEATHER DISTURBANCES FROM
MEXICO...ARE FORECAST TO INCREASE THE CHANCE OF AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS...MAINLY ACROSS ARIZONA...THIS
WEEKEND AND EARLY NEXT WEEK.

&&

.DISCUSSION...
STORM ACTIVITY LIMITED TO SOUTHEAST ARIZONA THIS EVENING AND
TRENDING DOWNWARD AS OF THIS WRITING. MORE ACTIVITY FURTHER
SOUTHEAST OVER SONORA AND CHIHUAHUA BUT NOTHING EXTRAORDINARY.
ANTICIPATE THE DEBRIS CLOUDINESS TO DRIFT NORTH AND NORTHWESTWARD
OVERNIGHT AND INTO WEDNESDAY MORNING. IT MAY BE A BIT THICKER THAN
WHAT WE HAD TODAY BUT WE WILL BE STARTING OFF WARMER AND THE NET
EFFECT OVER SOUTH-CENTRAL ARIZONA WILL BE LITTLE CHANGE. WILL NUDGE
UP PHOENIX AREA MAX TEMP FOR WEDNESDAY LEADING TO A RECORD TYING
114. THIS COULD WIND UP BEING THE WRONG DIRECTION IF CLOUDS GET
THICK ENOUGH AND LINGER. WOULD STILL EXPECT AT LEAST 110 IN A
/COOLER/ SCENARIO. FURTHER WEST OVER SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA...SKIES WILL BE CLEAR AND SO ANOTHER FEW DEGREES OF
WARMING IS ON TRACK. 00Z NAM AND GFS INDICATE SOMETHING OF AN
INVERTED TROUGH MOVING ACROSS FAR NORTHWEST MEXICO AND SOUTHERN
ARIZONA WEDNESDAY THOUGH THIS FEATURE IS NOT DISTINCTLY OBVIOUS IN
THE SATELLITE IMAGERY. OF MORE IMPORTANCE...THEY BOTH DEPICT DEEPER
MOISTURE PUSHING FURTHER WEST AND IN TURN DEVELOP A BROADER AREA OF
CONVECTION FOR WEDNESDAY. NAM IS MORE AGGRESSIVE THAN GFS...A SWITCH
FROM 18Z RUNS. THUS GFS DOES WOULD SUGGEST STORMS OVER THE HIGHER
TERRAIN STRUGGLING TO SURVIVE ON THE LOW DESERTS BUT YIELDING
SIGNIFICANT OUTFLOWS. DEPENDING UPON WEDNESDAY CONVECTION THURSDAY
COULD ACTUALLY BE WARMER. BOTH NAM AND GFS ARE DRIER FOR SOUTHEAST
ARIZONA THURSDAY.

&&

.PREVIOUS DISCUSSION ISSUED 300 PM...
TONIGHT THROUGH THURSDAY...
A STRONG WARM-UP WAS UNDERWAY ACROSS THE FORECAST AREA...INCLUDING
THE SOUTH CENTRAL AZ DESERTS WHERE VARIABLE CLOUDS HAD DEVELOPED
EARLIER IN THE DAY...AND AN EARLY 109 DEG F TEMP IN PHOENIX AT 1245
PM (WHICH WAS OUR FORECAST HIGH FOR THE DAY).

EARLIER CONCERNS...SINCE AN EXCESSIVE HEAT WATCH WAS POSTED FOR ALL
THE DESERTS BETWEEN SOUTHEAST CA TO SOUTH CENTRAL AZ...WAS HOW MUCH
INSOLATION WOULD BE REDUCED...FROM THE CLOUDS/HUMIDITY...CAUSING A
REDUCTION IN THE POTENTIAL SURFACE HEATING. OBVIOUSLY TODAY THE
CLOUDS MADE LITTLE DIFFERENCE IN THE STRONG EARLY DAY WARM-UP.
THEREFORE SINCE THERE IS NO MAJOR MOISTURE SURGE FORECAST TONIGHT
AND WEDNESDAY...WE DECIDED TO UPGRADE THE EXCESSIVE HEAT WATCH TO A
WARNING FOR ALL THE LOWER DESERTS BETWEEN IMPERIAL CALIFORNIA AND
PHOENIX ARIZONA.

VARIABLE CLOUDS AND EVEN A FEW SHOWERS AND THUNDERSTORMS MAY BE IN
THE OFFING OVER THE MOUNTAINS EAST OF PHOENIX ON WED...WITH PERHAPS
A LATE DAY CONVECTIVE OUTFLOW BOUNDARY DESCENDING ONTO THE DESERTS
WITH POSSIBLE BLOWING DUST.

ON THURSDAY...A DRIER AIRMASS MOVES INTO THE REGION FROM THE EAST.
500 MB TEMPERATURES WARM TO AN UNSEASONABLE MINUS 4 DEG C INDICATING
STABILITY AND A REDUCED THREAT FOR MOUNTAIN AFTERNOON CONVECTION.
PRECIP PROBABILITIES WERE ALSO LOWERED IN THE MOUNTAINS EAST OF
PHOENIX.

FRIDAY THROUGH MONDAY...
COOLER AFTERNOON TEMPERATURES ARE FORECAST THIS PERIOD AS HIGHER
HUMIDITIES ARE EXPECTED...ALONG WITH A BETTER THREAT FOR AFTERNOON
AND EVENING CONVECTION.

&&

.CLIMATE...

RECORD HIGH TEMPERATURE FOR THE MIDDLE OF THE WEEK.

CITY        JULY 22       JULY 23      JULY 24
----        -------       -------      -------
PHOENIX   116 IN 2006   114 IN 2006  114 IN 2006
YUMA      116 IN 2006   115 IN 1959  117 IN 1943

&&

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

ANTICIPATE SLOW INCREASE OF DEBRIS CLOUDS FROM SOUTHEAST ARIZONA AND
SONORA OVERNIGHT TONIGHT AND LINGERING FOR MUCH OF THE DAYTIME
WEDNESDAY...BASES GENERALLY AOA 15 KFT. ANTICIPATE SOUTHWEST AND
WEST WINDS TRANSITION TO SOUTHEAST WINDS BY SUNRISE AND LINGER FOR
MUCH OF THE DAY. ANTICIPATE THUNDERSTORMS TO GET CLOSER TO PHOENIX
AREA AIRFIELDS WEDNESDAY EVENING. CONFIDENCE TOO LOW AT THIS POINT
TO INSERT TEMPO TSRA IN THE TAF/S BUT ANTICIPATE OUTFLOWS FROM
DISTANT STORMS TO BE MORE LIKELY.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
STRONG HIGH PRESSURE WILL REMAIN THE PREDOMINANT WEATHER FEATURE
ACROSS THE REGION. BIGGEST IMPACT WILL BE THE HEAT...WITH ABOVE
NORMAL TEMPERATURES LIKELY THROUGH EARLY NEXT WEEK. THE TREND WILL
BE TOWARDS INCREASING MOISTURE EACH DAY...THOUGH THUNDERSTORMS WILL
MAINLY BE CONCENTRATED IN THE HIGHER TERRAIN OF EASTERN AZ. ACROSS
THE LOWER DESERTS OF AZ...ISOLATED THUNDERSTORMS WILL BE
POSSIBLE...PARTICULARLY DURING THE WEEKEND...THOUGH THE GREATER
THREAT IS FOR OUTFLOW BOUNDARIES CAPABLE OF PRODUCING STRONG WIND
GUSTS. FURTHER WEST ACROSS SE CA...THE CHANCE FOR RAIN AND
THUNDERSTORM IMPACTS WILL BE EVEN LOWER. MINIMUM HUMIDITIES WILL
GENERALLY FALL INTO A 15-20 PERCENT RANGE WITH GOOD OVERNIGHT
RECOVERY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...EXCESSIVE HEAT WARNING FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING AZZ020>023-025>028.

CA...EXCESSIVE HEAT WARNING FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING CAZ031>033.

&&

$$

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

DISCUSSION...AJ
PREVIOUS DISCUSSION...VASQUEZ
CLIMATE...MO
AVIATION....AJ
FIRE WEATHER...HIRSCH





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