Flash Flood in Arizona, August 18, 2003

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
945 AM MST MON AUG 18 2003

.SYNOPSIS...SOUTHEAST ARIZONA WILL CONTINUE TO SEE A LIMITED CHANCE
OF SHOWERS AND THUNDERSTORMS THE NEXT COUPLE OF DAYS AS THE UPPER
LEVEL LOW PRESSURE SYSTEM OVER WYOMING AND COLORADO CONTINUES TO
SHIFT FURTHER NORTHEAST AND HIGH PRESSURE BUILDS INTO THE REGION FROM
THE WEST. THE HIGH THEN BECOMES CENTERED OVER THE FOUR CORNERS REGION
BY MID WEEK...ALLOWING ADDITIONAL MOISTURE TO BE REINTRODUCED FROM
THE SOUTHEAST.

.DISCUSSION...
A FEW SHOWERS AND THUNDERSTORMS LINGER THIS MORNING OVER COCHISE
COUNTY...OTHERWISE SCATTERED MID LEVEL CLOUDS ARE FILTERING THROUGH
THE SKY CAUSING SOME SPRINKLES. HIGH PRESSURE REMAINS THE DOMINATE
FEATURE OVER ARIZONA...BUT LOW PRESSURE TO THE NORTHEAST HAS WEAKENED
THE MONSOON FLOW OVER THE REGION. THIS HAS RESULTED IN FEWER
THUNDERSTORMS ACROSS SOUTHEASTERN ARIZONA AND A COOLER AIR MASS. THIS
MORNING/S KTUS SOUNDING INDICATES SOME WARMING AT THE LOWER AND MID
LEVELS OVER YESTERDAY/S SOUNDING AND SOME COOLING ALOFT. AS FOR
PRECIPITABLE WATER...THE SATELLITE BRANCH OF NESDIS INDICATES THAT
THEY HAVE INCREASED OVER YESTERDAY DUE TO LAST NIGHTS OUTFLOW FROM
THE MCS OVER NORTHWEST MEXICO. BUT...STABILITY REMAINS THE SAME AS
YESTERDAY...SO TODAY SHOULD BRING A SLIGHTLY BETTER CHANCE OF SHOWERS
AND THUNDERSTORMS COMPARED TO SUNDAY. BEYOND TODAY...THE UPPER LEVEL
WEATHER PATTERN IS EXPECTED TO SHIFT ALLOWING THE HIGH PRESSURE
CENTER TO MOVE EASTWARD TOWARD THE FOUR CORNERS BRINGING BACK THE
BETTER CHANCES FOR THUNDERSTORMS.  EVANS

.TWC...NONE.

AZZ019-029>035-191400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1158 AM MST MON AUG 18 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...THUNDERSTORMS ARE FORECAST TO DEVELOP THIS AFTERNOON AND
INTO EARLY EVENING. HOWEVER...THE AREAL EXTENT WILL BE LIMITED AS A
WEAKNESS ALOFT WILL RESULT IN A VERY WEAK STORM MOTION. THEREFORE...
THE PROBABILITY FOR PRECIPITATION IN EXCESS OF ONE INCH WILL BE NEAR
CLIMATOLOGY IN THE MOUNTAINS...WITH BELOW CLIMATOLOGICAL CHANCES IN
THE VALLEYS. THE THREAT OF DAMAGING THUNDERSTORM DOWNBURST WINDS
WILL REMAIN LOW. A DISTURBANCE MOVING INTO SOUTHERN ARIZONA LATE
THIS EVENING WILL BRING ALLOW SCATTERED SHOWERS AND THUNDERSTORMS TO
PERSIST OVERNIGHT.

DISCUSSION....THE MORNING UPPER AIR BALLOON SOUNDING FROM TUCSON
INDICATED THAT ATMOSPHERE HAS BECOME SLIGHTLY MORE UNSTABLE ALOFT
WITH A COUPLE OF DEGREES OF COOLING ABOVE 600 MB. IN ADDITION...THE
STEERING FLOW ALOFT REMAINS QUITE WEAK...WHICH WILL HINDER THE
CHANCES FOR STORMS THAT DO DEVELOP THIS AFTERNOON OVER THE HIGHER
TERRAIN FROM MOVING ACROSS VALLEY LOCATIONS...THUS REDUCING THE
OVERALL AREAL COVERAGE. ALTHOUGH THIS WILL REDUCE THE CHANCES FOR
HEAVY PRECIPITATION IN THE VALLEYS...IT WILL INCREASE THE
PROBABILITY FOR MOUNTAIN LOCATIONS TO RECEIVE PRECIPITATION IN
EXCESS OF ONE INCH.

LATER THIS EVENING...A MID LEVEL DISTURBANCE NEAR GUYMAS WILL PUSH
NORTHWARD INTO SOUTHERN ARIZONA. THIS DISTURBANCE...AIDED BY AN AREA
OF UPPER LEVEL DIFFLUENCE...WILL REGENERATE SCATTERED SHOWERS AND
THUNDERSTORMS BEGINNING LATE THIS EVENING AND PERSISTING OVERNIGHT.
ALTHOUGH THESE STORMS WILL NOT BE STRONG SINCE THEY ARE OUT OF PHASE
WITH THE MAXIMUM DIURNAL HEATING...THE POSSIBILITY FOR LOCALLY HEAVY
PRECIPITATION WILL EXIST AS SOUTHERN ARIZONA WILL ALSO BE
EXPERIENCING AN INCREASE IN LOW LEVEL MOISTURE FROM THE SOUTH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

THUNDERSTORM ACTIVITY WILL BE INCREASING IN AREAL COVERAGE AROUND
MID WEEK AS HIGH PRESSURE BUILDS BACK OVER THE REGION AND BECOMES
CENTERED NEAR THE FOUR CORNERS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.