Severe Thunderstorm Warning 19, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-250545-

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
300 PM SAT JUL 24 2004

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

.SYNOPSIS...
HIGH PRESSURE ALOFT WILL REMAIN OVER ARIZONA THIS WEEKEND. MEANWHILE
...LOW PRESSURE SYSTEMS MOVING WEST ACROSS MEXICO AND THE GULF OF
CALIFORNIA WILL HELP INCREASE MOISTURE TONIGHT AND SUNDAY. THUS...AN
INCREASING CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS IS EXPECTED FOR THE WEEKEND. THE THREAT FOR
THUNDERSTORMS WILL BE CONFINED TO SOUTH-CENTRAL ARIZONA BY THE
MIDDLE OF NEXT WEEK...AS A LOW PRESSURE SYSTEM DEVELOPS ALONG THE
CALIFORNIA COAST...AND PUSHES THE UPPER HIGH SOUTH TOWARD THE
MEXICAN BORDER. AS THE LOW DEVELOPS IT WILL SPREAD DRIER AIR INTO
SOUTHEAST CALIFORNIA AND WESTERN ARIZONA AND ELIMINATE THE CHANCES
FOR WEATHER IN THAT AREA.

&&

.DISCUSSION...
UPPER HI HAS SHIFTED TO THE NWRN PART OF THE STATE...GIVING A
MODERATE NELY STEERING FLOW TO MUCH OF THE CWA...ESPECIALLY THE ERN
HALF. SKIES CLEARED NICELY TODAY UPSTREAM AND SCT STORMS HAVE
DEVELOPED GIVEN THE GOOD HEATING AND AMPLE MOISTURE AVAILABLE...AND
THESE STORMS SHOULD BE ABLE TO ADVECT SOUTH INTO THE SOUTHCENTRAL
DESERTS TONIGHT. IT MIGHT BE A REAL ACTIVE NIGHT BUT FOR A COUPLE OF
FACTORS. ONE...AIRMASS OVER SCNTRL AZ NOT AS WET AND UNSTABLE AS IT
WAS FRI...WITH 850MB DEWPOINT DOWN TO AROUND 11C...AND THE CAPE IS
LESS THAN 1000 J/KG. SURFACE DEWPOINTS AROUND THE DESERTS ARE DOWN
AS WELL AND AT 2 PM WERE RUNNING MOSTLY IN THE MID TO UPPER 50S.
ALSO...MOST OF THE FORCING AND DIFLUENCE ALOFT WILL FOCUS OVER SERN
AZ TONIGHT...WHERE SUBSTANTIAL CLOUD COVER HAS REALLY INHIBITED
CONVECTION THUS FAR THIS AFTERNOON. STILL...CHANCE POPS FOR
SOUTHCENTRAL AZ LOOK GOOD FOR TONIGHT AND THEY WILL CONTINUE TO BE
IN THE FORECAST. THERE MIGHT BE SOME STRONG GUSTY WINDS AND BLOWING
DUST IF THE STORMS ARE ABLE TO HOLD TOGETHER AND MOVE INTO THE
VALLEY...WITH THE SOMEWHAT DRIER AIR SEEN IN THE LOWER LEVELS OF THE
AMS GIVING A MODIFIED INVERTED VEE CHARACTER TO THE SOUNDING.
WESTERN ZONES HAVE A SLIGHT CHANCE...INTO THE ERN PORTION OF THE CA
ZONES...AS THE STORMS MAY BE ABLE TO WORK WESTWARD IN THE STEERING
FLOW AND MOVE INTO THOSE AREAS LATER TONIGHT. BASIC PATTERN DOES NOT
CHANGE FOR SUNDAY...AND EXPECT A REPEAT PERFORMANCE WITH A CHANCE
FOR LATE AFTN/EVE STORMS IN THE SOUTH-CENTRAL...AND A SLIGHT CHANCE
OUT WEST. DEPENDING ON HOW MUCH CONVECTION DEVELOPS TODAY AND HOW
MUCH THE LOWER AMS IS WORKED OVER...WE WILL SEE A BIT MORE OR
POSSIBLY LESS ACTION TOMORROW...BUT ONLY TIME WILL TELL ON THAT.

MODEL TRENDS CONTINUE TO SHOW THAT TROFFING WILL DEVELOP ALONG THE
CA COAST DURING THE MIDDLE PART OF NEXT WEEK...AND BY MONDAY THE
STEERING FLOW WILL SHIFT TO A NLY DIRECTION...THEN BECOME NWLY
TUESDAY. BY WED WLY TO NWLY STEERING FLOW WILL AFFECT MOST OF THE
CWA AND CONFINE THE THREAT FOR AFTN/EVE STORMS TO THE AREA AT AND
EAST OF PHOENIX. THUS THERE WILL BE DECREASING POPS AND WEATHER FROM
THE WEST BEGINNING MONDAY NIGHT AND CONTINUING THRU THE REST OF NEXT
WEEK. LITTLE CHANGE HAS BEEN MADE TO THE FORECAST IN THE EXTENDED
..WITH ONE MINOR CHANGE TO REMOVE ANY CHANCE FOR SHOWERS OR STORMS
FROM THE PHOENIX ZONE DURING THE AFTERNOON HOURS. CLIMATOLOGY AND
THE FLOW PATTERN MAKE IT VERY UNLIKELY THAT STORMS WILL AFFECT THE
PHOENIX METRO AREA BETWEEN NOON AND 5 PM ON THOSE DAYS.

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

&&
11

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1042 AM MST SAT JUL 24 2004

AZZ022>024-027-028-250500-
GREATER PHOENIX AREA-NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
NORTHWEST MARICOPA COUNTY-SOUTHERN GILA/TONTO NF FOOTHILLS-
SOUTHWEST MARICOPA COUNTY-
1042 AM MST SAT JUL 24 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH-CENTRAL ARIZONA.

.DAY ONE...TODAY

DAMAGING WIND WILL BE THE MAIN THREAT BETWEEN 5 PM AND 10 PM...MAINLY
OVER THE DESERTS. TREES...POWER LINES...AND POORLY CONSTRUCTED
BUILDINGS WILL BE MOST AT RISK. BLOWING DUST IS ALSO POSSIBLE IN THE
DESERTS AFTER 5 PM...AND VISIBILITIES MAY BE LOWERED TO BELOW ONE
MILE IN PLACES. STAY TUNED TO NOAA WEATHER RADIO OR YOUR LOCAL MEDIA
OUTLETS FOR POSSIBLE WATCHES OR WARNINGS.

SCATTERED THUNDERSTORMS MAY CAUSE HEAVY RAINS AND FLOODING OF POOR
DRAINAGE AND LOW LYING AREAS. WASHES MAY BEGIN FLOWING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS A CONTINUED CHANCE FOR MAINLY EVENING THUNDERSTORMS SUNDAY
THROUGH TUESDAY...AND THESE STORMS MAY PRODUCE BRIEF HEAVY RAIN ALONG
WITH STRONG GUSTY WINDS AND BLOWING DUST. THE CHANCE FOR STORMS WILL
BE LESS WEDNESDAY THROUGH SATURDAY...AS DRIER AIR MOVES IN FROM THE
WEST.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION IS LIKELY TODAY THROUGH SUNDAY...AND MAY BE NEEDED
MONDAY AND TUESDAY.

&&

FOR ADDITIONAL WEATHER INFORMATION...CHECK OUR WEB SITE AT
HTTP://WWW.WRH.NOAA.GOV/PHOENIX (IN SMALL LETTERS)

AZZ020-021-025-026-CAZ031-250500-
LOWER COLORADO RIVER VALLEY AZ-LOWER COLORADO RIVER VALLEY CA-
SOUTHWEST DESERTS-WEST CENTRAL DESERTS-
YUMA/MARTINEZ LAKE AND VICINITY-
1042 AM MST SAT JUL 24 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST ARIZONA AND THE LOWER
COLORADO RIVER VALLEY.

.DAY ONE...TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS A SLIGHT CHANCE FOR EVENING AND EARLY MORNING THUNDERSTORMS
SUNDAY THROUGH TUESDAY...WHICH COULD PRODUCE STRONG GUSTY
WINDS...SOME BLOWING DUST...AND BRIEF HEAVY RAINFALL.

&&

FOR ADDITIONAL WEATHER INFORMATION...CHECK OUR WEB SITE AT
HTTP://WWW.WRH.NOAA.GOV/PHOENIX (IN SMALL LETTERS)

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED SUNDAY THROUGH TUESDAY.

CAZ030-032-033-250500-
IMPERIAL COUNTY-JOSHUA TREE NATIONAL PARK-
RIVERSIDE COUNTY/EASTERN DESERTS-
1042 AM MST SAT JUL 24 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

&&

FOR ADDITIONAL WEATHER INFORMATION...CHECK OUR WEB SITE AT
HTTP://WWW.WRH.NOAA.GOV/PHOENIX (IN SMALL LETTERS)