Severe Thunderstorm Warning 27, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-271045-

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
915 PM MON JUL 26 2004

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

.SYNOPSIS...
MOISTURE WILL CONTINUE OVER THE AREA WITH A POSSIBILITY OF SHOWERS
AND THUNDERSTORMS TONIGHT. BY TUESDAY NORTHWESTERLY FLOW FROM A HIGH
PRESSURE AREA NEAR THE SOUTHERN CALIFORNIA COAST WILL SPREAD DRIER
AIR FROM THE NORTHWEST IN OUR REGION. THIS WILL CONFINE A SLIGHT
CHANCE OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO THE
HIGHER TERRAIN EAST OF THE GREATER PHOENIX AREA BY WEDNESDAY. THE
DRY WEATHER IS EXPECTED OVER THE ENTIRE AREA BY THURSDAY AND FRIDAY.
THIS HIGH PRESSURE CENTER WILL MOVE EAST TO NEW MEXICO BY THE
WEEKEND...HELPING TO BRING A RETURN OF MOISTURE AND A SLIGHT CHANCE
OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS BACK TO SOUTH
CENTRAL ARIZONA.

&&

.DISCUSSION...
PLENTY OF MOISTURE AVAILABLE FOR CONVECTION ACROSS AZ TODAY...WITH
GOES PWAT IMAGERY SHOWING A PLUME OF UP TO 1.5 INCHES EXTENDING UP
OVER MOST OF SRN AZ THIS EVE...AND THE 00Z PSR RAOB SHOWED 1.33
INCHES. SURFACE DEWPOINTS OVER THE AZ DESERTS STILL A BIT ON THE
SKIMPY SIDE THO...RUNNING MAINLY IN THE MID TO UPPER 50S AS OF 8 PM
THIS EVENING. UPPER HIGH NOW SITUATED OFF THE SRN CA COAST...WITH A
NWLY STEERING FLOW IN EFFECT OVER MOST OF THE CWA...AS SEEN IN THE
WATER VAPOR IMAGERY AS WELL AS THE VAD WIND PROFILE DATA AND EVE
SOUNDINGS. FOR THE MOST PART THIS AFTERNOON AND EVE...STORMS HAVE
FORMED OVER CENTRAL AZ...NORTH OF OUR NRN CWA BORDER...THEN DRIFTED
TO THE SE AND MAINLY AFFECTED THE AREA NORTH AND EAST OF PHOENIX
...WITH ZONE 24 SEEING MOST OF THE STORMS. RATHER STRONG CONVECTION
THAT DEVELOPED OVER SRN YAVAPAI COUNTY AND MOVED INTO FAR NRN ZONE
23 SENT STRONG OUTFLOW TO THE SOUTHWEST THAT RANGED FROM 20 TO 40
MPH IN PLACES. FOR THE MOST PART AS THE OUTFLOW MOVED SOUTH AND WEST
NO NEW STORMS WERE TRIGGERED...AS THE AIRMASS OVER THE CENTRAL
DESERTS STILL A BIT MOISTURE STARVED. IF THOSE BOUNDARIES COMING
FROM THE NORTH HAD MET OTHER OUTFLOW COMING FROM THE SOUTHEAST THEN
STRONG STORMS MIGHT HAVE FIRED UP OVER THE PHOENIX AREA...BUT WE
HAVE NOT SEEN THOSE BOUNDARIES MOVING FROM THE SE AS CONVECTION HAS
BEEN LIMITED THERE TODAY.

TONIGHT MAY BE SOMEWHAT OF A REPEAT PERFORMANCE FROM WHAT HAPPENED
LAST NIGHT...AS A CLUSTER OF STORMS CONTINUED TO DEVELOP OVER SRN
YAVAPAI COUNTY AS OF 9 PM...WITH THE DEVELOPMENT MORE AND MORE TO
THE WEST OVER THE PAST FEW HOURS. WITH THE STEERING FLOW FROM THE
NW...THIS MEANS A BETTER CHANCE FOR THOSE STORMS TO MOVE INTO
CENTRAL MARICOPA COUNTY AND THE PHOENIX METRO AS THE NIGHT WEARS
ON...AND THERE COULD BE MORE STORMS AND SHOWERS IN THE AREA AT AND
AFTER MIDNIGHT. THERE APPEARS TO BE ANOTHER SHORT WAVE MOVING AROUND
THE HIGH AND THRU NRN AND CENTRAL AZ TONIGHT...AND THIS CAN BE SEEN
IN THE PLOT DATA AS WELL AS THE VAPOR IMAGERY...WHERE SIGNIFICANT
DIFLUENCE ASSOCD WITH THE UPPER SHORT WAVE IS NOTED OVER CENTRAL AZ.
ETA FORECASTS THIS SHORT WAVE TO MOVE TO THE SE TONIGHT...AND THIS
WILL ADD DYNAMICS TO THE MIX AND ALLOW THE STORMS TO MAINTAIN SOME
ORGANIZATION FOR SOME HOURS TO COME. SOME CHANGES TO THE FORECAST
FOR TONIGHT MAY BE MADE TO REFLECT THE INCREASED CHANCE FOR STORMS
TO CONTINUE PAST MIDNIGHT OVER OUR ERN CWA. OTHERWISE FORECAST LOOK
OK...BASIC TRENDS ARE FINE. AS WE HEAD INTO THE MIDDLE OF THE
WEEK...FLOW BECOMES INCREASINGLY WESTERLY OR NORTHWESTERLY AND THIS
SPREADS DRIER AIR INTO OUR CWA FROM THE WEST.

IOP FOR INCREASED RAOBS FOR NAME PROJECT...MONSOON SUPPRESSION 00Z
WED TO 00Z FRI.

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.

&&

11

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1000 AM MST MON JUL 26 2004

AZZ024-262254-
SOUTHERN GILA/TONTO NF FOOTHILLS-
1000 AM MST MON JUL 26 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL ARIZONA.

.DAY ONE...TODAY

SCATTERED AFTERNOON AND EVENING THUNDERSTORMS MAY PRODUCE LOCALLY
HEAVY RAINS WHICH MAY CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW
LYING AREAS. WASHES MAY BEGIN FLOWING. STORMS MAY ALSO PRODUCE STRONG
GUSTY WINDS.

DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SCATTERED AFTERNOON AND EVENING THUNDERSTORMS TUESDAY WILL BECOME
ISOLATED ON WEDNEDAY. THE STORMS MAY PRODUCE LOCALLY HEAVY RAINS
WHICH MAY CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW LYING AREAS.
WASHES MAY BEGIN FLOWING. STORMS MAY ALSO PRODUCE STRONG GUSTY WINDS.
NO HAZARDOUS WEATHER IS EXPECTED ON THURSDAY AND FRIDAY. THERE WILL
BE A SLIGHT CHANCE OF THUNDERSTORMS ON SATURDAY AND SUNDAY.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND TONIGHT.

AZZ022-023-027-028-262254-
GREATER PHOENIX AREA-NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
NORTHWEST MARICOPA COUNTY-SOUTHWEST MARICOPA COUNTY-
1000 AM MST MON JUL 26 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL ARIZONA.

.DAY ONE...TODAY

ISOLATED AFTERNOON AND EVENING THUNDERSTORMS MAY PRODUCE LOCALLY
HEAVY RAINS WHICH MAY CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW
LYING AREAS. WASHES MAY BEGIN FLOWING. STORMS MAY ALSO PRODUCE STRONG
GUSTY WINDS.

DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

ISOLATED LATE AFTERNOON AND EVENING THUNDERSTORMS TUESDAY MAY PRODUCE
LOCALLY HEAVY RAINS WHICH MAY CAUSE MINOR FLOODING OF POOR DRAINAGE
AND LOW LYING AREAS. WASHES MAY BEGIN FLOWING. STORMS MAY ALSO
PRODUCE STRONG GUSTY WINDS. NO HAZARDOUS WEATHER IS EXPECTED ON
WEDNESDAY THROUGH SATURDAY. THERE WILL BE A SLIGHT CHANCE OF LATE
AFTERNOON AND EVENING THUNDERSTORMS ON SUNDAY.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING.

AZZ020-021-025-026-CAZ030>033-262254-
IMPERIAL COUNTY-JOSHUA TREE NATIONAL PARK-
LOWER COLORADO RIVER VALLEY AZ-LOWER COLORADO RIVER VALLEY CA-
RIVERSIDE COUNTY/EASTERN DESERTS-SOUTHWEST DESERTS-
WEST CENTRAL DESERTS-YUMA/MARTINEZ LAKE AND VICINITY-
1000 AM MST MON JUL 26 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA.

.DAY ONE...TODAY

ISOLATED AFTERNOON AND EVENING THUNDERSTORMS MAY PRODUCE LOCALLY
HEAVY RAINS WHICH MAY CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW
LYING AREAS. WASHES MAY BEGIN FLOWING. STORMS MAY ALSO PRODUCE STRONG
GUSTY WINDS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING.