Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 050308
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
808 PM MST TUE AUG 4 2015

.SYNOPSIS...
MOSTLY CLEAR SKIES AND DRY WEATHER WILL PREVAIL ACROSS THE REGION
THROUGH WEDNESDAY...WITH HIGH TEMPERATURES ON THE LOWER DESERTS
RANGING FROM 112 TO 115 DEGREES. MONSOON HUMIDITY WILL RETURN TO THE
AREA THURSDAY AND FRIDAY...PROVIDING A THREAT OF AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS ALONG WITH COOLER AFTERNOON
TEMPERATURES REGION WIDE. A MORE STABLE AND DRIER PATTERN WILL SHIFT
MOST OF THE MONSOON MOISTURE AND THREAT FOR SHWRS INTO EASTERN
ARIZONA THIS WEEKEND.

&&

.DISCUSSION...
MID EVENING WATER VAPOR AND RADAR IMAGERY PAINT A QUIET PICTURE
ACROSS THE AREA...WITH HIGH PRESSURE PARKED OVER ARIZONA AND
UNFAVORABLE SOUTHWESTERLY FLOW ACROSS MOST OF THE REGION. NOT
SURPRISINGLY...THIS HAS SIGNIFICANTLY SUPPRESSED CONVECTION ACROSS
THE AREA /EXCEPT FOR A CLUSTER ACROSS SONORA/...DRIED OUT THE
ATMOSPHERE /PWATS OBSERVED AT 0.77 INCHES IN PHOENIX AND 0.98 IN
TUCSON/...AND ALLOWED TEMPERATURES TO WARM UP INTO THE 111-113
RANGE EARLIER TODAY. GIVEN THE WARM AFTERNOON...TEMPERATURES HAVE
BEEN SLOW TO FALL THUS FAR WITH 03Z READINGS GENERALLY IN THE 100-104
RANGE.

FORECAST LOOKS ON TRACK FOR THE REST OF THE EVENING GIVEN
OBSERVATIONAL TRENDS AND INCOMING 00Z MODEL GUIDANCE. EXPECTING
SIMILAR LOWS TO THOSE SEEN ON TUESDAY...GENERALLY MID 80S IN THE
URBAN AREAS AND UPPER 70S/LOWER 80S IN THE OUTLYING DESERT LOCALES.
NO SIGNIFICANT CHANGES NECESSARY AT THIS POINT.

&&

.PREVIOUS DISCUSSION...
WEDNESDAY...
THE EXCESSIVE HEAT WARNING WILL CONTINUE INTO WEDNESDAY.
DRY STABLE AIR ALONG WITH INCREASING ATMOSPHERIC HEIGHT AND THICKNESS
VALUES PORTEND A SLIGHTLY WARMER WEDNESDAY OVER TODAY TUESDAY.
HOWEVER BY LATE IN THE DAY WEDNESDAY...CONVECTION OVER NORTHWEST
MEXICO WITH INCREASING MID/UPPER LEVEL SOUTH WINDS WILL BEGIN TO
IMPORT INCREASING CLOUDS INTO SOUTHERN AZ BY EVENING. MID/HIGH LEVEL
CLOUDS WILL BE FOLLOWED BY INCREASING LOW LEVEL MOISTURE INTO
SOUTHERN AZ THURSDAY.

THURSDAY AND FRIDAY...SOUTHERLY LOW LEVEL WINDS WILL ARE FORECAST TO
ADVECT INCREASING AMOUNTS OF LOW LEVEL MONSOON MOISTURE INTO SOUTHERN
AZ. A THREAT OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
THURSDAY HAS BEEN EXTENDED TO PORTIONS OF SOUTHEAST CA AND SOUTHWEST
AZ. MODELS FORECAST AN UPPER LEVEL AXIS OF DILITATION...OR
DEFORMATION ZONE AOA 300 MB TO SPREAD INTO SOUTHEAST CA/SOUTHWEST AZ
THURSDAY AFTERNOON FOR A LITTLE UPPER LEVEL SUPPORT OVER INCREASING
MOISTURE. THE THREAT OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS THURSDAY WILL CONTINUE OVER PORTIONS OF THE SOUTH
CENTRAL AZ DESERTS AND MTNS.

MODELS CONTINUE TO FORECAST A DRYING TREND IN SOUTHEAST CA AND
SOUTHWEST AZ WHICH WILL SPREAD MOISTURE AND A THREAT OF AFTN/EVE
SHWRS/TSTMS INTO THE EASTERN PORTIONS OF AZ...GENERALLY FROM PHOENIX
EASTWARD.

SATURDAY AND SUNDAY...A DRIER AND MORE STABLE AIRMASS WILL SPREAD
INTO OUR FORECAST AREA FROM THE WEST THIS WEEKEND...AND EXCEPT FOR A
SLIGHT CHANCE OF AFTERNOON SHOWERS AND THUNDERSTORMS OVER THE HIGHER
TERRAIN AND MOUNTAINS OF SOUTHERN GILA COUNTY/ZONE 24...THE REMAINDER
OF THE FORECAST AREA WILL BE DRY.

MONDAY AND TUESDAY...MODELS CONTINUE TO SUGGEST A SIGNIFICANT UPPER
LEVEL INVERTED TROUGH TO MOVE INTO FAR SOUTHEAST AZ MONDAY AFTERNOON
AND CONTINUE NORTH TOWARD PHOENIX MONDAY NIGHT. THIS COULD BE A
SIGNIFICANT SHWR/TSTM EVENT...HOWEVER SINCE THIS SYSTEM IS STILL TOO
FAR AWAY...THE BEST APPROACH IS TO INTRODUCE A THREAT OF SHOWERS AND
THUNDERSTORMS OVER SOUTH CENTRAL AZ MONDAY...MONDAY NIGHT AND
TUESDAY.

&&

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

MOSTLY CLEAR SKIES AND LIGHT DIURNALLY DRIVEN WINDS WILL PREVAIL AT
ALL TAF SITES THROUGH AT LEAST LATE WEDNESDAY NIGHT. NO WEATHER-
RELATED AVIATION CONCERNS ANTICIPATED.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
AN INCREASE IN MOISTURE WILL BRING CHANCES OF AFTERNOON AND EARLY
EVENING SHOWERS AND THUNDERSTORMS TO SOUTH CENTRAL ARIZONA ON FRIDAY
WHILE ACTIVITY WILL BE MOSTLY LIMITED TO HIGHER TERRAIN AREAS EAST OF
PHOENIX FOR THE WEEKEND. AN ADDITIONAL MOISTURE SURGE WILL THEN
INCREASE CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN ARIZONA
FOR EARLY NEXT WEEK. MINIMUM RELATIVE HUMIDITIES OF 15 TO 20 PERCENT
RANGE WILL BE COMMON FOR MUCH OF THE PERIOD ACROSS THE DESERTS. HIGH
TEMPERATURES WILL BE AROUND OR SLIGHTLY ABOVE NORMAL. WINDS WILL BE
LIGHT THROUGH MUCH OF THE PERIOD FOLLOWING TYPICAL DIURNAL DIRECTIONS
EXCEPT FOR AFTERNOON UPSLOPE BREEZES GUSTING AT TIMES UP TO 20 MPH.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...EXCESSIVE HEAT WARNING FROM 11 AM TO 8 PM MST WEDNESDAY FOR
     AZZ020>023-025>028.

CA...EXCESSIVE HEAT WARNING FROM 11 AM TO 8 PM PDT WEDNESDAY FOR
     CAZ031>033.

&&

$$

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

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...KUHLMAN



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