Severe Thunderstorm Warning 56, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
240 PM MST TUE AUG 28 2001

.SYNOPSIS...HIGH PRESSURE OFF THE COAST OF SOUTHERN CALIFORNIA WILL
CONTINUE TO SHIFT WESTWARD THROUGH THE WEEK...ALLOWING TEMPERATURES
TO FALL TO NEAR NORMAL VALUES BY THIS WEEKEND. MOISTURE FROM THE
SOUTH AND EAST WILL HELP TO INITIATE SOME AFTERNOON AND EVENING
THUNDERSTORMS THROUGH THE UPCOMING HOLIDAY WEEKEND...BUT THEY WILL
BE MAINLY CONFINED TO THE MOUNTAINS.

.DISCUSSION...UPPER LEVEL HIGH PRESSURE OFF THE NORTHERN BAJA COAST
CONTINUES TO RETROGRADE SLOWLY WESTWARD. AS IT DOES...TEMPERATURES
WILL COOL SLIGHTLY EACH DAY THROUGH THE WEEK ACROSS SOUTHERN ARIZONA
AS THE THICKNESSES AND HEIGHTS BEGIN TO LOWER. NORTH TO NORTHWEST
FLOW AROUND THE HIGH HAS ALLOWED COOLER MID AND UPPER LEVEL
TEMPERATURES TO FILTER INTO THE REGION AS NOTED BY THE KTUS AND KPHX
12Z SOUNDINGS. A FAIRLY SIGNIFICANT GULF SURGE HAS ALSO TAKEN PLACE
TODAY (WITH KYUX VAD WIND PROFILER SHOWING SOUTHERLY FLOW UP TO 7
KFT AT ONE TIME)...WITH INCREASING SURFACE DEWPOINTS AND PW VALUES.
PRECIPITABLE WATER IMAGERY SHOWS VALUES IN EXCESS OF 1 INCH ACROSS
THE WESTERN DESERTS AND ALONG THE MEXICAN AND NEW MEXICO BORDERS.
WITH THIS UNSTABLE ENVIRONMENT (COOLER MID LEVELS AND WARM SURFACE
READINGS)...ISOLATED STORMS HAVE BROKEN OUT OVER THE HIGHER TERRAIN
IN EASTERN PORTIONS OF THE CWA. THIS AREA IS ALSO ALONG EASTERN
FRINGES OF THE UPPER LEVEL HIGH...WHERE THE SUBSIDENCE INVERSION IS
A LITTLE WEAKER.

THE AVN AND ETA BOTH DID A POOR JOB HANDLING THE GULF SURGE TODAY...
HOWEVER THEY DO INDICATE SOME INCREASING MOISTURE ACROSS PORTIONS OF
SOUTHERN ARIZONA THIS WEEK...MAINLY FROM TUCSON EAST. DUE TO THE
UNCERTAINTY OF THE MODELS...OR IF THE SURGE MOISTURE WILL HOLD IN
PLACE OR WASH OUT LIKE THE LAST ONE DID (A DAY OR SO AGO)... WILL
ONLY GO WITH A SLIGHT CHANCE THUNDERSTORMS WEDNESDAY AND THURSDAY AT
THIS TIME. AGAIN THE BEST CHANCES WILL BE FROM TUCSON EAST AND OVER
THE HIGHER TERRAIN. THE AVN DOES SHOW A COMPLEX DEVELOPING OVER
WESTERN NEW MEXICO TONIGHT. IF THIS DOES HAPPEN...ADDITIONAL
MOISTURE WOULD BE TRANSPORTED INTO THE EASTERN ZONES...INCREASING
THE CHANCE FOR STORMS ON WEDNESDAY. WILL HOLD OFF ON THIS SCENARIO
FOR NOW...BUT SOMETHING THE EVENING SHIFT NEEDS TO LOOK AT.

ON THE EXTENDED...UPPER HIGH BEGINS TO REPOSITION ITSELF NORTH AND
EAST OF THE AREA...WHICH SHOULD ALLOW FOR BETTER AND DEEPER MOISTURE
TO WORK INTO THE REGION. WILL GO WITH A CHANCE OF AFTERNOON AND
EVENING THUNDERSTORMS FROM TUCSON EAST AND A SLIGHT CHANCE OUT WEST
EACH DAY.  ZELL

.TWC...NONE.

AZZ019-029>035-290700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1115 AM MST TUE AUG 28 2001

.SYNOPSIS...ANOTHER MOISTURE SURGE HAS DEVELOPED FROM NORTHERN
SONORA AND ALONG THE GULF OF CALIFORNIA...INCREASING SURFACE
MOISTURE ACROSS SOUTHERN ARIZONA. IN ADDITION...THE MID LEVELS OF
THE ATMOSPHERE HAVE MOISTENED UP AND COOLED OFF. THE BEST CHANCES
FOR STORM DEVELOPMENT WILL BE OVER THE HIGHER TERRAIN FROM TUCSON
EAST TO THE NEW MEXICO BORDER. ANY STORMS THAT DEVELOP WILL HAVE THE
POTENTIAL FOR STRONG GUSTY WINDS...HOWEVER DUE TO THE DRIER LOWER
LEVELS THE THREAT OF FLASH FLOODING WILL BE VERY LOW.

.DISCUSSION...SURFACE DEWPOINTS HAVE INCREASED CONSIDERABLY THIS
MORNING ACROSS SOUTHERN ARIZONA...FROM THE MID 40S AT 6 AM INTO THE
50S AND LOWER 60S AT 10 AM. THIS IS DUE TO A MOISTURE SURGE FROM
NORTHERN SONORA AND THE GULF OF CALIFORNIA. IN ADDITION...THE MID
LEVELS OF THE ATMOSPHERE HAVE MOISTENED UP AND COOLED OFF CREATING
AN UNSTABLE ATMOSPHERE FOR STORM DEVELOPMENT. WITH AMPLE SURFACE
HEATING THE HIGHER TERRAIN FROM TUCSON EAST WILL HAVE THE MOST
FAVORABLE ENVIRONMENT FOR STORM DEVELOPMENT...ALTHOUGH IT IS STILL
UNCERTAIN IF THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND EVENING.
ANY STORMS THAT DO DEVELOP WILL HAVE THE POTENTIAL FOR STRONG GUSTY
WINDS.

STORM MOTION WILL BE TO THE SOUTH-SOUTHEAST AROUND 15 MPH.

ZELL