Severe Thunderstorm Warning 4, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-200545-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
305 PM MST MON JUN 19 2000

.SYNOPSIS...
MOISTURE-LADEN AIR FROM THE GULF OF CALIFORNIA HAS OVERSPREAD
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA. THIS WILL LEAD TO
AFTERNOON AND EVENING THUNDERSTORMS OVER PORTIONS OF SOUTH CENTRAL
ARIZONA THROUGH WEDNESDAY. LOCALLY HEAVY RAINFALL IS POSSIBLE ON
WEDNESDAY AS A WEAK UPPER DISTURBANCE APPROACHES THE AREA.

.DISCUSSION...
SCATTERED THUNDERSTORMS HAVE DEVELOPED OVER NORTHERN PINAL AND
SOUTHERN GILA COUNTIES THIS AFTERNOON...WITH REPORTS OF GUSTY WINDS
AND SOME BLOWING DUST. ISSUED A SVR EARLIER THIS AFTN FOR INTENSE
STORM NORTH OF SAN CARLOS. CAPE IMPRESSIVE OVER SOUTH CENTRAL
DESERT...1000-1500 J/KG...SO OUTFLOWS FROM STORMS SOUTH OF PHX COULD
TRIGGER A FEW STORMS OVER AND EAST OF METRO PHOENIX THIS EVENING
...WITH STRONG GUSTY WINDS AND SOME BLOWING DUST AS WELL AS BRIEF
HEAVY RAIN POSSIBLE.

AVN SEEMS TO HAVE A REASONABLE HANDLE ON SITUATION NEXT FEW DAYS
...AND ETA HAS BECOME MORE MOIST OVER TIME IN LOWER TROPOSPHERE WHICH
IS MORE REFLECTIVE OF CURRENT CONDITIONS. SO...AM NOT CONVINCED
MOISTURE WILL BE SHIFTED FAR ENOUGH EAST TO REMOVE CHANCE FOR STORMS
SOUTH CENTRAL AZ TUESDAY AND TUESDAY EVENING. WEAK DISTURBANCE
APPROACHES FORECAST AREA FROM THE SOUTH TUESDAY NIGHT AND
WEDNESDAY...AND GIVEN ITS WARM CORE CHARACTER AND LOCATION IN
DEFORMATION ZONE BETWEEN TWO HIGH CENTERS...AM CONCERNED THAT LOCALLY
HEAVY RAINFALL COULD OCCUR OVER PORTIONS OF SOUTH CENTRAL AZ LATE
TUESDAY NIGHT...BUT MORE LIKELY WEDNESDAY AND WEDNESDAY EVENING SO
FORECAST HAS THAT SLANT TO IT. WITH LOWER LEVEL FLOW BACKING FROM SW
TO SE IN ADVANCE OF DISTURBANCE...CHANCE FOR PRECIP SPREADS TO ALL OF
SOUTHWEST AZ BY WEDNESDAY.

IN EXTENDED...BEST DYNAMICS SHIFT JUST TO OUR EAST AND NORTH...BUT
ENOUGH LOW LEVEL MOISTURE REMAINS TO WARRANT A CHANCE FOR STORMS OVER
HIGHER TERRAIN MAINLY EAST OF PHOENIX. ELSEWHERE...MAY SEE A FEW
DEGREES OF WARMING...BUT NOT MUCH OF A CHANGE FROM WHAT'S BEEN
OCCURRING. DG

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AZZ022>024-027-028-200700-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1121 AM MST MON JUN 19 2000

...SLIGHT RISK FOR HAZARDOUS WEATHER OVER CENTRAL AND EASTERN
MARICOPA...NORTHERN PINAL...AND SOUTHERN GILA COUNTIES THIS
AFTERNOON AND TONIGHT...

THE SLIGHT RISK AREA INCLUDES THAT PORTION OF SOUTH-CENTRAL
ARIZONA ALONG AND EAST OF A LINE EXTENDING FROM WICKENBURG TO
GILA BEND. THE GREATER PHOENIX METROPOLITAN AREA IS INCLUDED IN
THE SLIGHT RISK AREA...AS ARE CASA GRANDE...FLORENCE...COOLIDGE...
APACHE JUNCTION...SUPERIOR...GLOBE...AND MIAMI. THE GREATEST THREATS
FROM STORMS...IN ADDITION TO CLOUD TO GROUND LIGHTNING...WILL BE THE
POTENTIAL FOR BRIEF BUT LOCALLY HEAVY RAIN...VERY STRONG WINDS...AND
DENSE BLOWING DUST.

THE AIRMASS OVER SOUTHWEST ARIZONA HAS BECOME MORE MOIST THAN WAS
THE CASE SUNDAY...AND MOISTURE CONTINUES TO STREAM NORTH AND EAST
FROM THE GULF OF CALIFORNIA AND NORTHERN MEXICO. ALSO...THE
ATMOSPHERE IS MORE UNSTABLE OVER SOUTH-CENTRAL AND SOUTHEAST
ARIZONA TODAY. ALL THESE FACTORS INCREASE THE CHANCE FOR
ISOLATED SEVERE THUNDERSTORMS OVER THE SLIGHT RISK AREA THIS
AFTERNOON AND EARLY TONIGHT. STORMS ARE LIKELY TO DEVELOP A LITTLE
EARLIER TODAY THAN WHAT OCCURRED SUNDAY...WITH SOME STORMS IN THE
CENTRAL DESERT SOUTH AND EAST OF PHOENIX BY EARLY THIS AFTERNOON.

THE HAZARDOUS WEATHER OUTLOOK GIVES PRELIMINARY INFORMATION FOR THE
POSSIBILITY OF WEATHER THAT COULD BECOME SEVERE...DAMAGING WINDS IN
EXCESS OF 57 MPH...DENSE BLOWING DUST WITH VISIBILITY AT OR BELOW
1/4 MILE...HAIL 3/4 INCH IN DIAMETER OR LARGER... AND HEAVY RAINFALL
THAT COULD CAUSE FLOODING OR RUNNING WASHES.  WHEN SEVERE WEATHER OR
FLOODING BEGINS... IMPORTANT LIFE SAVING INFORMATION WILL BE
PROVIDED IN SHORT TERM FORECASTS...SEVERE WEATHER AND FLOOD
WARNINGS...AND IN FOLLOW-UP STATEMENTS.

STORM SPOTTER ACTIVATION MAY BE NECESSARY LATER TODAY.

DG

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