Severe Thunderstorm Warning 107, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-142245-

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
935 AM MST SUN AUG 14 2005

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

.SYNOPSIS...
A LOW PRESSURE SYSTEM FROM THE NORTHERN GULF OF CALIFORNIA IS MOVING
NORTH TOWARD ARIZONA TODAY...AND WILL MOVE ONLY VERY SLOWLY NORTH
OVER SOUTH-CENTRAL ARIZONA TONIGHT. THE RESULT WILL BE AN INCREASE IN
SHOWERS AND THUNDERSTORMS BY THIS AFTERNOON AND TONIGHT WITH SOME
VERY HEAVY RAIN AND FLASH FLOODING POSSIBLE IN SOUTH-CENTRAL
ARIZONA...ESPECIALLY SOUTHEAST AND EAST OF PHOENIX EASTWARD ACROSS
SOUTHERN GILA COUNTY. STRONG...GUSTY...DAMAGING WINDS AND ARE ALSO
POSSIBLE ALONG WITH DESERT BLOWING DUST. THE LOW PRESSURE SYSTEM WILL
MOVE NORTH WITH SHOWERS DECREASING FROM THE SOUTH BY MONDAY
AFTERNOON. DRIER AIR FROM THE SOUTHWEST WILL BRING MOSTLY SUNNY AND
WARMER DAYS TO MOST OF THE AREA TUESDAY THROUGH SATURDAY.

&&

.DISCUSSION...
THE FLOW ALOFT IS BECOMING EVEN MORE DYNAMICAL TODAY AS A COUPLE OF
SHORTWAVE FEATURES APPROACH THE AREA. THE FORMER UPPER LEVEL CENTRAL
BAJA CA CUTOFF LOW WAS MOVING INTO SOUTHEAST AZ THIS MORNING...WHILE
A LARGE PACIFIC TROF WILL APPROACH SOUTHERN CA LATER IN THE DAY. A
SORT OF ONE TWO PUNCH SO TO SPEAK FOR OUR AZ FORECAST ZONES IN
SOUTHWEST AND SOUTH CENTRAL AZ. LET US EXPLAIN.

THE FORMER BAJA CA CUTOFF LOW WAS MOVING INTO SOUTHEAST AZ (BEST
SEEN IN THE VAPOR IMAGERY)...AND ADVECTING A MUCH HIGHER 700-500 MB
THETA-E AIRMASS INTO SOUTH CENTRAL AZ. INCREASING JET DYNAMICS ACROSS
THE EASTERN THIRD OF AZ TODAY WILL PROVIDE A GOOD SHOWER
THUNDERSTORM ENVIRONMENT TO MUCH OF SOUTH CENTRAL AND PARTS OF
SOUTHWEST AZ TODAY. SHOWERS AND THUNDERSTORMS HAVE ALREADY BEEN ON
THE UPSWING THIS MORNING IN PINAL AND EASTERN MARICOPA COUNTIES...
INCLUDING THE GREATER PHOENIX...WITH MASSIVE STORMS AND VERY HEAVY
RAIN IN SOUTHEAST AZ AT 16Z.

THE MAIN WEATHER THREAT AGAIN WILL BE HEAVY RAIN AND POSSIBLE
LOCALIZED FLOODING THIS AFTERNOON AND EVENING. WE MAY HAVE TO
CONSIDER A FLASH FLOOD WATCH FOR MARICOPA...PINAL...AND SOUTHERN
GILA COUNTIES LATER IN THE DAY.

AS THE AIRMASS IN PARTS OF SOUTHWEST AND SOUTH CENTRAL AZ BECOMES
NEARLY SATURATED LATER TODAY AND THIS EVENING...THE PACIFIC LOW
PRESSURE SYSTEM MOVING TOWARD SOUTHERN CA WILL SPREAD AND
INCREASINGLY BROAD DIFLUENT UPPER LEVEL FLOW ACROSS MUCH OF AZ
TONIGHT AND MONDAY MORNING TO CONTINUE THE RAIN CHANCES OVERNIGHT.

DRYING AND A MORE STABLE AIRMASS FOLLOWS LATER MONDAY ...TUESDAY...
AND SUBSEQUENT DAYS.

FORECASTS WERE ALREADY UPDATED EARLIER THIS MORNING. SINCE SHOWER
AND THUNDERSTORM ACTIVITY WAS ISOLATED IN MARICOPA AND PINAL
COUNTIES AT 16Z...AND DIMINISHING SOMEWHAT...WE WILL CONTINUE KEEP
THE CHANCE FOR SHOWER WORDING INTACT. FORECASTS LOOK FOR NOW.

&&

.AVIATION...
DISCUSSION FOR 18Z TAFS. TAFS MOST LIKELY TO EXPERIENCE STORM
ACTIVITY WITHIN NEXT 12 HOURS ARE KIWA AND KPHX. AFTER INITIAL AREA
OF SHOWERS WITH EMBEDDED THUNDERSTORMS PASSES...IT IS ANTICIPATED
THAT THERE MAY BE SOMEWHAT OF A LULL IN ACTIVITY AROUND THE PHOENIX
METRO AREA DURING MIDDAY AND PART OF THE AFTERNOON. THEN VIGOROUS
STORM ACTIVITY IS ANTICIPATED TO DEVELOP BY LATE AFTERNOON OVER
PINAL AND GILA COUNTIES. HOW MUCH WILL SPILL INTO THE METRO AREA IS
UNCERTAIN...BUT THERE IS A DISTINCT POSSIBILITY OF THUNDERSTORMS
PASSING DIRECTLY OVER KPHX AND KIWA BETWEEN 23Z-06Z.

SEE TAFS PHXTAFPHX...PHXTAFIWA...PHXTAFYUM...LAXTAFBLH...LAXTAFIPL
FOR DETAILS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.
CA...NONE.

&&

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

VASQUEZ

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE PHOENIX AZ
602 AM MST SUN AUG 14 2005

AZZ020>028-CAZ030>033-150100-
GREATER PHOENIX AREA-IMPERIAL COUNTY-JOSHUA TREE NATIONAL PARK/JTNP/-
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 COUNTY/TONTO NATIONAL FOREST FOOTHILLS-
SOUTHWEST DESERTS-SOUTHWEST MARICOPA COUNTY-WEST CENTRAL DESERTS-
YUMA/MARTINEZ LAKE AND VICINITY-
602 AM MST (602 AM PDT) SUN AUG 14 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH-CENTRAL AND
SOUTHWEST ARIZONA.

.DAY ONE...TODAY

A LOW PRESSURE SYSTEM FROM THE NORTHERN GULF OF CALIFORNIA IS
MOVING TOWARD ARIZONA TODAY AND WILL BRING AN INCREASE IN
SHOWERS AND THUNDERSTORMS BY THIS AFTERNOON AND TONIGHT MAINLY TO
SOUTH-CENTRAL ARIZONA INCLUDING THE GREATER PHOENIX AREA. SOME OF
THESE STORMS WILL PRODUCE VERY HEAVY RAIN WITH AN INCREASING
POSSIBILITY OF FLASH FLOODING ESPECIALLY SOUTHEAST AND EAST OF
PHOENIX EASTWARD ACROSS SOUTHERN GILA COUNTY WHERE MUDSLIDES ARE
ALSO POSSIBLE. STRONG GUSTY DAMAGING WINDS ARE ALSO POSSIBLE WITH
SOME OF THE THUNDERSTORMS...AS WELL AS BLOWING DESERT DUST WITH A
SUDDEN REDUCTION IN VISIBILITY.

IF YOU GET CAUGHT IN A DUST STORM...PULL OFF THE ROAD AS FAR AS
POSSIBLE...PUT YOUR VEHICLE IN PARK...TURN YOUR LIGHTS ALL THE
WAY OFF...AND TAKE YOUR FOOT OFF THE BRAKE.

STAY AWAY FROM FLOODED ROADS EVEN IF YOU THINK IT IS ONLY A SMALL
AMOUNT OF WATER. THE DEPTH OF THE WATER MAY BE GREATER THAN YOU
THINK...AND RUNNING WATER HAS GREAT FORCE. TURN AROUND AND FIND A
SAFE WAY TO GET TO YOUR DESTINATION.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

SHOWERS AND THUNDERSTORMS WILL DECREASE FROM THE SOUTH BY MONDAY
AFTERNOON. HOWEVER...ROADS MAY STILL BE FLOODED WITH WATER RUNNING IN
NORMALLY DRY WASHES AND CREEKS MAINLY IN SOUTH-CENTRAL ARIZONA
INCLUDING THE GREATER PHOENIX AREA.

.SPOTTER INFORMATION STATEMENT...

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

ELLIS