Flash Flood Warning 17, NWS Phoenix, AZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
440 PM MST THU JUL 15 2010

.UPDATED...UPDATED AVIATION DISCUSSION

&&

.SYNOPSIS...
EXCESSIVELY HOT WEATHER IS EXPECTED TO CONTINUE THROUGH THE WEEKEND
AS STRONG HIGH PRESSURE ALOFT CONTINUES OVER THE SOUTHWESTERN UNITED
STATES. THERE IS A SLIGHT CHANCE OF AFTERNOON AND EVENING SHOWERS
AND THUNDERSTORMS MAINLY IN THE HIGHER TERRAIN EAST OF THE GREATER
PHOENIX AREA THROUGH FRIDAY...AND IN SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA TODAY INTO THIS EVENING. SOME MOISTURE INCREASE WITH WEAK
LOW PRESSURE SYSTEMS FROM THE EAST IS EXPECTED TO RESULT IN A
SOMEWHAT BETTER CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS THIS WEEKEND.

&&

.DISCUSSION...
TEMPERATURES WERE GENERALLY A COUPLE OF DEGREES WARMER IN
SOUTH-CENTRAL ARIZONA EARLY THIS AFTERNOON COMPARED WITH THE SAME
TIME YESTERDAY. MEANWHILE...TEMPERATURES WERE GENERALLY 5 TO 15
DEGREES COOLER IN SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA DUE TO
COOLING FROM SHOWERS WITH THE AIR SPREADING NORTH EVEN WHERE SHOWERS
HAD NOT OCCURRED.

WITH WARM OVERNIGHT LOW TEMPERATURES EXPECTED ACROSS THE AREA...HAVE
EXTENDED THE EXCESSIVE HEAT WARNING ACROSS THE ENTIRE DESERT AREA
FROM SOUTHEAST CALIFORNIA TO SOUTHWEST AND SOUTH-CENTRAL ARIZONA
THROUGH 8 PM FRIDAY EVENING AND FOR SOUTH-CENTRAL ARIZONA INCLUDING
THE GREATER PHOENIX AREA THROUGH THE WEEKEND TO 8 PM SUNDAY EVENING.

A WEAK LOW PRESSURE SYSTEM WILL CONTINUE MOVING WEST AND THE
ISOLATED TO SCATTERED SHOWERS THAT HAVE BEEN OVER SOUTHEAST
CALIFORNIA ARE EXPECTED TO CONTINUE MOVING WEST INTO SAN DIEGO AND
WESTERN RIVERSIDE COUNTIES. THUS...EXPECT THESE SHOWERS TO COME TO
AN END IN THE IMPERIAL COUNTY AND EASTERN RIVERSIDE COUNTY DESERT
AREAS THIS EVENING AND IN JOSHUA TREE NATIONAL PARK BY LATE THIS
EVENING. SOME OF THE THUNDERSTORMS COULD PRODUCE STRONG GUSTY
WINDS...DANGEROUS CLOUD TO GROUND LIGHTNING AND LOCALLY HEAVY RAIN.

AS MENTIONED IN THE DISCUSSION THIS MORNING...THE BEST CHANCE OF
SHOWERS AND THUNDERSTORMS INTO THIS EVENING IS IN JOSHUA TREE
NATIONAL PARK AS THE SYSTEM LOOKS AS IF IT IS HAVING ITS GREATEST
EFFECT FROM NORTHERN BAJA CALIFORNIA INTO SAN DIEGO COUNTY AND
WESTERN RIVERSIDE COUNTY INTO THIS EVENING.

WITH THE WEAK LOW PRESSURE SYSTEM MOVING WEST AWAY FROM SOUTH-CENTRAL
ARIZONA INCLUDING THE GREATER PHOENIX AREA...IT LOOKS AS IF MOST OF
THE SOUTH-CENTRAL ARIZONA DESERT AREAS...ESPECIALLY THE GREATER
PHOENIX AREA WILL STAY DRY TONIGHT AND PROBABLY FRIDAY NIGHT. HAVE
LEFT A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS BETWEEN GILA BEND
AND CASA GRANDE MAINLY OVER THE SOMEWHAT ELEVATED TERRAIN....AND THE
HIGHER TERRAIN EAST OF THE GREATER PHOENIX AREA THROUGH THIS EVENING
AND AGAIN FRIDAY AFTERNOON AND EVENING.

SOME MOISTURE INCREASE WITH WEAK LOW PRESSURE SYSTEMS FROM THE EAST
IS EXPECTED TO RESULT IN A SOMEWHAT BETTER CHANCE OF MAINLY
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS THIS WEEKEND.

PREVIOUS DISCUSSION...
LOW LEVEL MONSOON MOISTURE WILL CONTINUE TO COVER THE ENTIRE
FORECAST AREA SATURDAY...BUT NOT CHANGE MUCH IN QUANTITY. WINDS
ALOFT...ABOVE 300 MB...WILL BE LIGHT AND SLIGHTLY DIVERGENT ACROSS
THE FORECAST AREA...PARTICULARLY SOUTHWEST AND SOUTH CENTRAL AZ.
THEREFORE A THREAT OF AFTERNOON/EVENING THUNDERSTORMS WILL CONTINUE
JUST ABOUT EVERYWHERE. THE BIGGEST STORM THREAT OF COURSE WILL BE
OVER THE MOUNTAINS NORTH AND EAST OF PHOENIX...INCLUDING OUR ZONE 24.

LOW LEVEL MONSOON MOISTURE IS FORECAST TO INCREASE SUBSTANTIALLY
THIS PERIOD...AND MAY BECOME EXCESSIVE /I.E. 850-800 MB DEWPOINTS
ABOVE 14 C/ OVER THE SOUTHEAST QUARTER OF AZ. HOWEVER...THERE ARE
MODEL DISCREPANCIES REGARDING THE FLOW ALOFT...OR REGARDING UPPER
LEVEL FEATURES THAT CAN TRIGGER CONVECTIVE EVENTS. THEREFORE IT WILL
BE PRUDENT...SINCE ELEVATED MOISTURE LEVELS ARE EXPECTED...TO
CONTINUE THE THREAT OF AFTERNOON AND EVENING SHOWERS AND THUNDER
STORMS AREA-WIDE EARLY NEXT WEEK.

&&

.AVIATION...
SOUTH-CENTRAL AZ...INCLUDING KPHX KIWA AND SURROUNDING AIRFIELDS...
CONVECTION STILL LIMITED TODAY AND SHOULD REMAIN MOSTLY OVER THE
HIGHER TERRAIN NORTH AND EAST OF PHOENIX. HOWEVER...POTENTIAL EXISTS
FOR OUTFLOW WINDS TO WORK INTO THE CENTRAL DESERTS AND AFFECT
KPHX/KIWA AFTER ABOUT 02Z. AT TAF TIME CONVECTION TOO FAR AWAY TO
TIME ANY WIND SHIFTS INTO THE EVE TAFS...SO LEAVING WESTERLY WINDS
THRU THE EVENING HOURS. WILL MONITOR AND UPDATE TAFS SHOULD WIND
SHIFTS BECOME MORE APPARENT. OTHERWISE...EXPECT WINDS TO TEND
TOWARDS EXPECTED EASTERLY VALUES AFTER MIDNIGHT...THEN WILL SHIFT
BACK TO THE WEST AFTER 18Z FRIDAY.

SOUTHERN CALIFORNIA...INCLUDING KIPL AND KBLH...
CONVECTION APPEARS TO BE SHIFTING OFF TO THE WEST AND SHOULD NOT
AFFECT THE AIRPORTS THIS EVENING...BUT THERE WILL REMAIN A SLIGHT
CHANCE FOR A THUNDERSTORM UNTIL ABOUT 04Z. WINDS HAVE TAPERED OFF
AND SHOULD STAY FROM THE SOUTHWEST LESS THAN 20 MPH OVERNIGHT
TONIGHT AND KIWA/KBLH. EXPECT WINDS TO SHIFT TO THE SOUTHEAST AT
KIPL AFTER 12Z...AND STRENGHTEN FROM THE SOUTH ALONG THE RIVER BY
LATE MORNING...WITH SOME AFTERNOON SLY GUSTS OVER 20KT AT KBLH. NO
SIGNIFICANT AVIATION CONCERNS AT THE TAF LOCATIONS NEXT 24 HOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DAYTIME HUMIDITY VALUES SHOULD HOVER AROUND 15 PERCENT THROUGH THE
WEEKEND. MODELS CURRENTLY SUGGEST THAT HIGH PRESSURE MAY BE SHIFTED
SOUTH AS A TROF MOVES THROUGH THE NORTHERN ROCKIES...INITIATING A
BRIEF DRYING TREND ACROSS MOST OF ARIZONA...IN ADDITION TO VERY HOT
DAYTIME TEMPERATURES IN EXCESS OF 113 OVER THE LOWER DESERTS. BY
MONDAY...THE UPPER LEVEL HIGH CONSOLIDATES AND SHIFTS BACK EAST...
ALLOWING FOR A DEEPER MOIST SOUTHERLY FLOW FROM MEXICO BACK INTO THE
STATE. WITH THE MOISTURE INCREASE...DAYTIME TEMPERATURES WILL FALL A
FEW DEGREES AND THE THREAT OF THUNDERSTORMS WILL RETURN TO THE LOWER
DESERT LOCATIONS OF SOUTHEAST CA/SOUTHWEST AZ...AND HIGHER TERRAIN
OF SOUTH-CENTRAL ARIZONA.

&&

.CLIMATE...

             PHOENIX                       YUMA
         FCST  NORM      REC        FCST  NORM     REC
JULY 16  114   107   118/1925       113   107  116/1960*
JULY 17  113   107   116/2005       110   107  117/2005

* MULTIPLE YEARS WITH MOST RECENT SHOWN

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...EXCESSIVE HEAT WARNING FOR SOUTH-CENTRAL ARIZONA DESERT AREAS OF
     MARICOPA COUNTY...AND NORTHWEST AND NORTH-CENTRAL PINAL COUNTY
     INCLUDING THE GREATER PHOENIX AREA...GILA BEND...AND CASA GRANDE
     ZONES 22...23...27...AND 28...UNTIL 8 PM MST SUNDAY.

     EXCESSIVE HEAT WARNING FOR SOUTHWEST ARIZONA DESERT AREAS OF
     YUMA COUNTY AND LA PAZ COUNTY INCLUDING THE CITY OF YUMA AND
     THE LOWER COLORADO RIVER VALLEY...ZONES 20...21...25...AND 26...
     UNTIL 8 PM FRIDAY.

CA...EXCESSIVE HEAT WARNING FOR SOUTHEAST ARIZONA DESERT AREAS OF
     IMPERIAL COUNTY AND EASTERN RIVERSIDE COUNTY INCLUDING THE
     LOWER COLORADO RIVER VALLEY...ZONES 31...32...AND 33...UNTIL
     UNTIL 8 PM FRIDAY.

&&

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...ELLIS/VASQUEZ
AVIATION...CB
FIRE WEATHER...MEYERS
CLIMATE...CB/INIGUEZ

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
545 AM MST THU JUL 15 2010

AZZ022-023-027-028-161300-
NORTHWEST MARICOPA COUNTY-GREATER PHOENIX AREA-
SOUTHWEST MARICOPA COUNTY-NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
545 AM MST THU JUL 15 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH-CENTRAL
ARIZONA.

.DAY ONE...TODAY AND TONIGHT

AN EXCESSIVE HEAT WARNING IS IN EFFECT THROUGH FRIDAY NIGHT DUE TO
THE COMBINATION OF VERY HOT DAYTIME TEMPERATURES IN THE 111-115
DEGREE RANGE...AND OVERNIGHT LOWS IN THE UPPER 80S TO LOWER 90S.

ALSO...THERE IS A SLIGHT CHANCE OF EVENING THUNDERSTORMS.
THUNDERSTORM HAZARDS INCLUDE LIGHTNING...STRONG WINDS...AND AREAS OF
DENSE BLOWING DUST.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE EXCESSIVE HEAT WARNING WILL REMAIN IN EFFECT THROUGH FRIDAY
NIGHT. THERE IS A CHANCE THAT VERY HOT AFTERNOON TEMPERATURES MAY
EXTEND INTO SATURDAY AND SUNDAY.

THERE IS A SLIGHT CHANCE FOR LATE AFTERNOON AND EVENING THUNDER
STORMS FRIDAY THROUGH WEDNESDAY. THUNDERSTORM HAZARDS INCLUDE
LIGHTNING...STRONG WINDS...AND DENSE BLOWING DUST.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ020-021-025-026-CAZ031>033-161300-
LOWER COLORADO RIVER VALLEY AZ-WEST CENTRAL DESERTS-
YUMA/MARTINEZ LAKE AND VICINITY-SOUTHWEST DESERTS-
LOWER COLORADO RIVER VALLEY CA-RIVERSIDE COUNTY/EASTERN DESERTS-
IMPERIAL COUNTY-
545 AM MST THU JUL 15 2010 /545 AM PDT THU JUL 15 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME SOUTHWEST
ARIZONA...EXTREME WEST-CENTRAL ARIZONA...SOUTHWEST ARIZONA...WEST-
CENTRAL ARIZONA AND EXTREME SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS. THUNDERSTORM HAZARDS
INCLUDE STRONG WIND...DENSE BLOWING DUST...AND LIGHTNING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

AN EXCESSIVE HEAT WATCH IS IN EFFECT FOR FRIDAY. VERY HOT
TEMPERATURES IN THE 115 TO 117 DEGREE RANGE WILL DEVELOP. THERE ARE
INDICATIONS THAT VERY HOT AFTERNOON TEMPERATURES MAY ALSO EXTEND
INTO SATURDAY AND SUNDAY.

A SLIGHT CHANCE OF LATE AFTERNOON AND EVENING THUNDERSTORMS WILL
CONTINUE THROUGH TUESDAY. PRIMARY THUNDERSTORM HAZARDS INCLUDE
STRONG WIND...DENSE BLOWING DUST...AND LIGHTNING.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ024-161300-
SOUTHERN GILA COUNTY/TONTO NATIONAL FOREST FOOTHILLS-
545 AM MST THU JUL 15 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST-CENTRAL
ARIZONA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS.
THUNDERSTORM HAZARDS INCLUDE FREQUENT LIGHTNING...BRIEF HEAVY
RAIN...SUDDEN WIND GUSTS TO 50 MPH...AND SMALL HAIL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS WILL CONTINUE
THROUGH WEDNESDAY. THUNDERSTORM HAZARDS INCLUDE FREQUENT
LIGHTNING...BRIEF HEAVY RAIN...SUDDEN GUSTS TO 50 MPH...AND SMALL
HAIL.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

CAZ030-161300-
JOSHUA TREE NATIONAL PARK-
545 AM PDT THU JUL 15 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS.
THUNDERSTORM HAZARDS INCLUDE STRONG WIND...DENSE BLOWING DUST...AND
FREQUENT LIGHTNING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

VERY HOT TEMPERATURES WILL DEVELOP FRIDAY AND THE WEEKEND. THOSE
PLANNING OUTDOOR ACTIVITIES SHOULD TAKE PRECAUTIONS TO AVOID
DEHYDRATION. IN ADDITION...A SLIGHT CHANCE OF THUNDERSTORMS IS
EXPECTED. THUNDERSTORM HAZARDS INCLUDING STRONG WIND...DENSE BLOWING
DUST...AND FREQUENT LIGHTNING.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

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