Flash Flood in Arizona, September 6, 2003

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
215 PM MST SAT SEP 6 2003

.SYNOPSIS...MOISTURE WILL DECREASE A BIT AS DRIER AIR MOVES IN FROM
THE NORTHWEST SUNDAY. A WEAK UPPER LEVEL SYSTEM WILL MOVE INTO THE
STATE TUESDAY...ONCE AGAIN INCREASING THE COVERAGE OF THUNDERSTORMS.
DRY FLOW BEHIND A TROUGH MOVING THROUGH THE GREAT BASIN WILL LIKELY
ONCE AGAIN THIN STORMS OUT BY THURSDAY.

.DISCUSSION...STILL QUITE RESPECTABLE PRECIPITABLE WATER VALUES
IN THE 1.2 TO 1.4 INCH RANGE ACROSS MOST OF SOUTHEAST ARIZONA.
SURFACE DEWPTS RANGING FROM THE 60S WEST TO MIDDLE 50S FAR EAST.
GOOD ENOUGH. THE FLOW DOESNT LOOK QUITE AS WEEK TODAY...BUT STORM
MOVEMENT (OR ANY ATTEMPT THEREOF) IS STILL BELOW 10 KTS. IN
ADDITION...SUBSIDENCE INVERSION NEAR H5 NOT INCONSIDERABLE. THIS HAS
ALL ADDED TOGETHER TO MAKE FOR AN EARLY AFTERNOON WHERE CONVECTION
HAS FIRED FAIRLY WELL OVER HIGHER TERRAIN...BUT IS NOT MAKING IT
INTO VALLEY LOCATIONS YET. RAPID DEVELOPMENT HAS HAD A HARD TIME
PUSHING THROUGH THE INVERSION...BUT ANOTHER FEW DEGREES OF HEATING
COULD SERVE TO PUNCH THROUGH AS WELL AS HELP STORMS SPREAD A LITTLE
BETTER INTO VALLEYS FROM OUTFLOWS. SCATTERED COVERAGE FOR LATE
AFTERNOON AND EVENING LOOKS GOOD.

GENERAL NORTHWESTERLY FETCH UNDER BUCKLING RIDGE SHOULD BRING IN A
DRYING TREND SUNDAY AND MONDAY. TROPICAL IMPULSE OFF BAJA PENINSULA
IS DRAWN UP JUST AHEAD OF DECENT WEST COAST TROUGH AND INTO ARIZONA
TUESDAY. SOUTHERLY COMPONENT TO FLOW AT THIS POINT WILL ALSO IMPORT
MOISTURE...SHOULD END UP BEING SOME DECENT STORMS AROUND TUESDAY
INTO WEDNESDAY. AFTER THAT SOME SORT OF DRYING TREND IS LIKELY IN
THE WAKE OF THE TROUGH. M

.TWC...NONE.

AZZ019-029>035-071400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1153 AM MST SAT SEP 6 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...HIGH PRESSURE WILL CONTINUE TO SHIFT TO THE WEST. THIS
WILL GRADUALLY REDUCE THE CHANCES FOR AFTERNOON AND EVENING SHOWERS
AND THUNDERSTORMS THROUGH MONDAY...HOWEVER WITH LINGERING MOISTURE
IN PLACE THERE WILL STILL BE A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS. A STORM SYSTEM WILL MOVE INTO THE PACIFIC NORTHWEST
EARLY NEXT WEEK...DRAGGING A TROUGH ACROSS THE REGION AS IT MOVES
EASTWARD DURING THE MIDDLE OF NEXT WEEK. AN INCREASE IN THUNDERSTORM
ACTIVITY IS EXPECTED AHEAD OF THIS FEATURE...AS MOISTURE GETS PULLED
NORTHWARD ACROSS THE REGION.

DISCUSSION...VERY SIMILAR TO THE LAST COUPLE OF DAYS...WITH A MOIST
AND UNSTABLE AIRMASS IN PLACE. THE 12Z KTUS SOUNDING INDICATES A
PRECIPITABLE WATER VALUE OF 1.41 INCHES...WHICH IS UP 0.18 INCHES
FROM YESTERDAY. GOES TOTAL PRECIPITABLE WATER IMAGERY INDICATES
VALUES RANGING FROM AROUND 1.6 INCHES OVER FAR WESTERN PORTIONS OF
THE FORECAST AREA...TO NEAR 0.80 INCHES IN THE SOUTHERN WHITE
MOUNTAINS. SURFACE DEWPOINTS ACROSS SOUTHERN ARIZONA ARE CURRENTLY
IN THE MID 50S TO MID 60S...WHICH IS 3 TO 5 DEGREES HIGHER THAN AT
THIS TIME YESTERDAY. THE 12Z KTUS RAOB ALSO INDICATES THAT THE
AIRMASS REMAINS MODERATELY UNSTABLE...WITH AN UNMODIFIED LIFTED
INDEX OF MINUS 4.5 AND A POSITIVE ENERGY VALUE OF 2718 J/KG.

FOR TODAY...EXPECT SCATTERED AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS ACROSS MOST OF SOUTHERN ARIZONA...WITH ISOLATED
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE TOHONO OODHAM
NATION AND FAR WESTERN PIMA COUNTY. CONVECTION HAS ALREADY DEVELOPED
OVER THE HIGHER TERRAIN OF THE WHITE MOUNTAINS...AS WELL AS THE SKY
ISLANDS OF SOUTHERN ARIZONA. SOME THESE STORMS WILL MOVE AND/OR
DEVELOP IN THE LOWERS DESERTS DURING THE AFTERNOON AND EVENING
HOURS. THE STEERING FLOW HAS INCREASED FROM YESTERDAY...AND WILL BE
EAST/NORTHEAST AT 10 TO 15 MPH. THE RISK OF ANY SEVERE THUNDERSTORMS
TODAY WILL BE LOW. THE PROBABILITY OF ONE INCH OR GREATER RAINFALL
WILL BE NEAR CLIMATOLOGY.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

THE MODELS INDICATE THERE WILL BE ENOUGH MOISTURE ACROSS SOUTHEAST
ARIZONA THROUGH WEDNESDAY FOR THE CHANCE OF AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS. AN UPSWING IN ACTIVITY IS EXPECTED ON
TUESDAY AND WEDNESDAY AS AN APPROACHING TROUGH FROM THE WEST ALLOWS
DEEPER MOISTURE TO GET PULLED UP ACROSS THE REGION. THE CHANCE FOR
SEVERE THUNDERSTORMS AND GREATER THAN ONE INCH OF RAINFALL WILL BE
NEAR CLIMATOLOGY SUNDAY THROUGH WEDNESDAY. BY THURSDAY AND FRIDAY...
PARTLY CLOUDY TO MOSTLY SUNNY CONDITIONS ARE EXPECTED AS THE TROUGH
MOVES TO THE EAST...AND DRIER AIR FILTER INTO THE REGION.

.SPOTTER INFORMATION STATEMENT...

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