Flash Flood Warning 18, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-291045-

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
915 PM MST TUE DEC 28 2004

SOUTHWEST AND SOUTH-CENTRAL ARIZONA...AND SOUTHEAST CALIFORNIA
FORECAST DISCUSSION

.SYNOPSIS...
A VIGOROUS LOW PRESSURE SYSTEM WILL MOVE ACROSS THE SOUTHWEST UNITED
STATES TONIGHT AND WEDNESDAY. RAIN SHOWERS AND A FEW THUNDERSTORMS
WILL CONTINUE TO DEVELOP OVER SOUTHEAST CALIFORNIA AND SOUTHWEST
ARIZONA THIS AFTERNOON...AND OVERSPREAD SOUTH-CENTRAL ARIZONA
TONIGHT AND WEDNESDAY. LOCALLY HEAVY RAIN IS POSSIBLE...ESPECIALLY
OVER EASTERN RIVERSIDE...LA PAZ...MARICOPA...AND SOUTHERN GILA
COUNTIES. THE LOW WILL MOVE EAST OF ARIZONA THURSDAY. HOWEVER...A
COUPLE OF WEATHER DISTURBANCES WILL BRING A SLIGHT CHANCE FOR RAIN
LATER THIS WEEK AND AGAIN EARLY NEXT WEEK...WITH SOMEWHAT COOLER
WEATHER POSSIBLE BY EARLY NEXT WEEK.

&&

.DISCUSSION...
THE LARGE CUTOFF LOW JUST OFF THE CENTRAL AND SOUTHERN CA COAST WAS
STARTING TO ACCELERATE TOWARD AZ THIS EVENING. THIS LARGE CUTOFF LOW
CONSISTED OF TWO LARGE EMBEDDED SHORTWAVES. ONE MOVED THROUGH
SOUTHERN CA TUES AFTERNOON WHILE THE SECOND SHORTWAVE...AT THE BASE
OF THE TROF...WILL ROTATE INTO AZ WED MORNING. AHEAD OF THESE
SHORTWAVES WAS A PLUME OF SUBTROPICAL MOISTURE THAT FED INTO
SOUTHEAST CA TUE AFTERNOON...AND WAS BEGINNING TO FEED INTO PORTIONS
OF SOUTH CENTRAL AZ...INCLUDING PHOENIX...THIS EVENING(03Z).

NEARLY TWO INCHES (1.86) OF RAIN FELL OVER THE HIGHER ELEVATIONS OF
SOUTHEAST CA (JOSHUA TREE NATIONAL PARK)THROUGH 00Z. A FLASH FLOOD
WARNING WAS ISSUED FOR THAT AREA... HOWEVER THERE WAS NO FEEDBACK OF
FLOODING. HOWEVER...FLOODED WASHES WERE REPORTED LATE TUE AFTERNOON
AT THE EASTERN END OF THE SALTON SEA WITH A CAR AND 3 PEOPLE
STRANDED IN A WASH.

AGAIN...COPIOUS AMOUNTS OF LOW LEVEL SUBTROPICAL MOISTURE WILL
CONTINUE TO FEED INTO THE ENTIRE FORECAST AREA TONIGHT. AS THE
SECOND SHORTWAVE APPROACHES...THERE IS POTENTIAL FOR HEAVY RAIN AND
FLOODING. A FLASH FLOOD WATCH CONTINUES FOR MOST OF THE FORECAST
AREA...GENERALLY FROM SOUTHEAST CA EAST TO SOUTH CENTRAL AZ...
PARTICULARLY THE UPSLOPE AREAS THROUGH WED AFTERNOON. PRECIP AMOUNTS
COULD EASILY APPROACH TWO INCHES BY WED MORNING IN MANY OF THE
UPSLOPE AREAS.

IT NOW APPEARS THAT THE WINDOW FOR HEAVIEST RAIN IN SOUTH CENTRAL
AZ...INCLUDING PHOENIX...WILL OCCUR TOWARD MORNING...WITH PRECIP
ESCALATING FROM THE SCATTERED SHOWERS GOING ON NOW (03Z). HEAVIEST
RAINS IN SOUTHEAST CA WILL OCCUR AFTER MIDNIGHT WITH THE VIGOROUS
APPROACH OF THE SHORTWAVE TROF.

SHOWERS AND OR PERIODS OF RAIN WILL BEGIN TO TAPPER OFF WED NIGHT AS
THE SHORTWAVE MOVES INTO NEW MEXICO. DRY CONDITIONS ARE EXPECTED THU.

CURRENT FORECASTS HITS THE WELL ADVERTIZED SYSTEM VERY HARD.
NO UPDATES NEEDED.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FLASH FLOOD WATCH IN EFFECT TODAY THROUGH 5 AM
     WEDNESDAY FOR ZONE 20
     FLASH FLOOD WATCH IN EFFECT TODAY THROUGH 5 PM WEDNESDAY FOR
     ZONE 21
     FLASH FLOOD WATCH FROM 5 PM TONIGHT THROUGH 5 PM WEDNESDAY FOR
     ZONES 22/23/24/28.

CA...FLASH FLOOD WATCH IN EFFECT TODAY THROUGH 4 AM WEDNESDAY FOR
     ZONES 30/31/32.

&&

VASQUEZ

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
559 AM MST TUE DEC 28 2004

AZZ020>024-028-CAZ030>032-282300-
GREATER PHOENIX AREA-JOSHUA TREE NATIONAL PARK-
LOWER COLORADO RIVER VALLEY AZ-LOWER COLORADO RIVER VALLEY CA-
NORTHWEST AND NORTH CENTRAL PINAL COUNTY-NORTHWEST MARICOPA COUNTY-
RIVERSIDE COUNTY/EASTERN DESERTS-SOUTHERN GILA/TONTO NF FOOTHILLS-
WEST CENTRAL DESERTS-
559 AM MST TUE DEC 28 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN RIVERSIDE COUNTY IN
CALIFORNIA...AS WELL AS LA PAZ...NORTHERN AND CENTRAL MARICOPA
...NORTHERN PINAL...AND SOUTHERN GILA COUNTIES IN ARIZONA.

.DAY ONE...TODAY

MODERATE TO HEAVY RAIN SHOWERS...AS WELL AS A FEW THUNDERSTORMS
...ARE EXPECTED TO DEVELOP THIS AFTERNOON AND TONIGHT OVER EASTERN
RIVERSIDE COUNTY INCLUDING JOSHUA TREE NATIONAL PARK IN CALIFORNIA
...AND LA PAZ COUNTY IN ARIZONA. LOCALLY HEAVY RAIN MAY RESULT IN
FLASH FLOODING...ESPECIALLY IN AND NEAR WASHES...SO A FLASH FLOOD
WATCH HAS BEEN ISSUED.

LOCALLY HEAVY RAIN IS POSSIBLE TONIGHT OVER NORTHERN AND CENTRAL
MARICOPA COUNTY INCLUDING THE GREATER PHOENIX AREA...SOUTHERN GILA
COUNTY...AND NORTHERN PINAL COUNTY IN ARIZONA. SOME FLOODING IS
POSSIBLE...SO A FLASH FLOOD WATCH HAS BEEN ISSUED.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

MODERATE TO HEAVY RAIN SHOWERS...AS WELL AS A FEW THUNDERSTORMS
...ARE EXPECTED OVER CENTRAL AND EASTERN LA PAZ COUNTY...NORTHERN AND
CENTRAL MARICOPA COUNTY INCLUDING THE GREATER PHOENIX AREA
...SOUTHERN GILA COUNTY...AND NORTHERN PINAL COUNTY ON WEDNESDAY.
SOME FLOODING IS POSSIBLE...SO A FLASH FLOOD WATCH HAS BEEN ISSUED
FOR THIS AREA.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE REQUIRED TODAY AND WEDNESDAY.

AZZ025>027-CAZ033-282300-
IMPERIAL COUNTY-SOUTHWEST DESERTS-SOUTHWEST MARICOPA COUNTY-
YUMA/MARTINEZ LAKE AND VICINITY-
559 AM MST TUE DEC 28 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR IMPERIAL COUNTY IN
CALIFORNIA...AND YUMA AND SOUTHWEST MARICOPA COUNTY IN ARIZONA.

.DAY ONE...TODAY

RAIN SHOWERS...AND A FEW THUNDERSTORMS...WILL BE POSSIBLE THIS
AFTERNOON AND TONIGHT. BRIEF HEAVY RAIN COULD RESULT IN MINOR
FLOODING OF POOR DRAINAGE AND LOW LYING AREAS...AS WELL AS CITY
STREETS. WASHES MAY BEGIN FLOWING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

RAIN SHOWERS...AND A FEW THUNDERSTORMS...WILL OCCUR WEDNESDAY.
BRIEF HEAVY RAIN COULD RESULT IN MINOR FLOODING OF POOR DRAINAGE AND
LOW LYING AREAS...AS WELL AS CITY STREETS. WASHES MAY BEGIN FLOWING.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED TODAY AND WEDNESDAY.

DG