Severe Thunderstorm Warning 15, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-270545-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
405 PM MST SAT JUL 26 2003

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE WILL INTERACT WITH A RATHER UNSTABLE AND
MOIST AIRMASS TO BRING A GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS
TO SOUTH CENTRAL AND WEST CENTRAL ARIZONA TONIGHT INTO EARLY SUNDAY.
A FEW STORMS COULD BE SEVERE OVER SOUTH CENTRAL ARIZONA THIS
EVENING...AND AREAS OF BLOWING DUST ARE LIKELY OVER THE LOWER DESERT
OF SOUTHWEST AND SOUTH CENTRAL ARIZONA. A SERIES OF WEATHER
DISTURBANCES WILL BRING AN INCREASED CHANCE FOR SHOWERS AND STORMS
TO THE LOWER DESERT SUNDAY AND MONDAY EVENINGS. MOIST EASTERLY FLOW
ALOFT WILL PERSIST THROUGH THE UPCOMING WEEK AS A STRONG UPPER HIGH
REMAINS CENTERED OVER NEVADA AND UTAH...WHICH SHOULD RESULT IN A
CHANCE FOR AFTERNOON THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH
CENTRAL ARIZONA...AS WELL AS SOME CHANCE FOR EVENING STORMS MAINLY
OVER THE SOUTH CENTRAL ARIZONA DESERT.

.DISCUSSION...
NO REAL CHANGE TO MORNING DISCUSSION...WITH TONIGHT STILL APPEARING
TO BE AN UP NIGHT REGARDING THUNDERSTORM POTENTIAL OVER THE
CENTRAL AND EASTERN PORTION OF OUR CWA. DECENT CHANCE FOR WIDESPREAD
MEASURABLE RAIN OVER SOUTH CENTRAL AZ...WITH LOCALLY HEAVY RAIN
POSSIBLE...AND COMBINATION OF FAVORABLE THERMODYNAMICS AND
KINEMATICS HAS PROMPTED SPC TO ISSUE A SEVERE THUNDERSTORM WATCH FOR
SOUTH CENTRAL ARIZONA UNTIL 9 PM. AS EXPECTED...STORMS HAVE FIRED
NICELY OVER EAST CENTRAL AND SOUTHEAST ARIZONA THIS AFTERNOON...AND
EXPECT DECENT OUTFLOWS FROM STORMS TO OUR EAST AND SOUTH TO HELP
TRIGGER STRONG STORMS OVER SOUTH CENTRAL ARIZONA TONIGHT. VERY
FAVORABLE COMBINATION OF UPPER LEVEL DIVERGENCE...ATMOSPHERIC
INSTABILITY ...VERTICAL SHEAR...AND FAVORABLE STEERING FLOW SUPPORTS
IDEA OF A RATHER WELL-ORGANIZED AREA OF STORMS (MCS?) PROPAGATING
OVER THE SOUTH CENTRAL DESERT TONIGHT...WHERE POPS ARE GREATEST.
COMPLEX OF STORMS MAY VERY WELL MAKE IT TO...OR SLIGHTLY WEST
OF...THE LOWER COLORADO RIVER VALLEY...WHERE LOWER POPS EXIST.

NEXT COUPLE OF NIGHTS WILL LIKELY BE ACTIVE FROM A CONVECTIVE
STANDPOINT ALSO...THOUGH DESERT LOCALES WHERE BOUNDARY LAYER IS
WORKED OVER TONIGHT PROBABLY WONT BE ABLE TO SUPPORT REALLY INTENSE
STORMS TOMORROW NIGHT. IF SUNDAY EVENING TURNS OUT TO BE RELATIVELY
QUIET OVER LOWER DESERT...MONDAY COULD WIND UP BEING ANOTHER UP
DAY...EVEN AS FAR WEST AS FAR SOUTHEAST CALIFORNIA. STRONG UPPER
HIGH FORECAST TO REMAIN OVER NEVADA OR UTAH THRU AT LEAST THURSDAY
...WITH TRAJECTORIES FAVORABLE FOR TAPPING INTO DECENT MOISTURE AND
WITH MID-LEVEL EASTERLY FLOW AT OR ABOVE CLIMO...SO EXPECT MODERATE
-GRADE MONSOON TO PERSIST...WITH STRONG AFTERNOON THUNDERSTORMS OVER
THE HIGHER TERRAIN AND SOME EVENING STORMS OVER THE LOWER DESERT.
DG

.PSR...SEVERE THUNDERSTORM WATCH FOR SOUTH CENTRAL ARIZONA ZONES
       22-23-24-27-28 UNTIL 9 PM MST (MARICOPA...NORTHERN PINAL...
       AND SOUTHERN GILA COUNTIES)...

AZZ020>028-CAZ030>033-270100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1145 AM MST SAT JUL 26 2003

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

.DAY ONE...TODAY

ISOLATED THUNDERSTORMS WITH GUSTY WINDS AND BRIEF MODERATE RAIN WILL
BE POSSIBLE OVER LA PAZ AND EASTERN RIVERSIDE COUNTIES TODAY AS A
WEATHER DISTURBANCE OVER SOUTHERN NEVADA MOVES SLOWLY TOWARD THE
NORTH. ANOTHER WEATHER DISTURBANCE IS EXPECTED TO MOVE INTO
SOUTHEAST ARIZONA BY THIS EVENING...THEN TRACK WEST ACROSS SOUTHERN
ARIZONA OVERNIGHT. SCATTERED THUNDERSTORMS WILL DEVELOP OVER THE
HIGHER TERRAIN OF SOUTH CENTRAL ARIZONA LATE THIS AFTERNOON...THEN
OVERSPREAD MUCH OF THE SOUTH CENTRAL DESERT TONIGHT. ISOLATED STORMS
WILL LIKELY REDEVELOP WESTWARD TO THE LOWER COLORADO RIVER VALLEY
AND FAR SOUTHEAST CALIFORNIA BY LATE TONIGHT. THE GREATEST RISK FOR
SEVERE WEATHER WILL BE OVER SOUTH-CENTRAL ARIZONA EARLY TONIGHT...
WITH DAMAGING STRAIGHT LINE WIND...LOCALLY HEAVY RAINFALL...AND
INTENSE CLOUD TO GROUND LIGHTNING POSSIBLE WITH STRONGEST STORMS.
DENSE BLOWING DUST MAY BE GENERATED BY STORMS WHICH FORM OVER OR
NEAR THE SOUTH-CENTRAL ARIZONA DESERT THIS EVENING...WITH SOME
BLOWING DUST POSSIBLY SPREADING WEST TOWARD SOUTHWEST ARIZONA LATER
TONIGHT.

.DAY TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

UNSETTLED WEATHER WILL CONTINUE SUNDAY INTO MONDAY AS MORE WEATHER
DISTURBANCES TRACK WESTWARD ACROSS THE AREA. LOCALLY HEAVY RAINFALL
AND STRONG GUSTY WINDS WILL BE THE PRIMARY WEATHER THREATS...WITH
LOCAL DAY TO DAY CHANGES IN ATMOSPHERIC STABILITY DETERMINING IN
LARGE PART HOW STRONG STORMS WILL BE. A MODERATE-GRADE MONSOON
PATTERN WILL BE IN PLACE TUESDAY THROUGH FRIDAY...SO EXPECT
SCATTERED LATE AFTERNOON THUNDERSTORMS OVER THE HIGHER TERRAIN OF
SOUTH CENTRAL ARIZONA AND ISOLATED STRONG EVENING AND NIGHTTIME
STORMS OVER THE LOWER DESERT OF SOUTH-CENTRAL AND SOUTHWEST ARIZONA.