Severe Thunderstorm Warning 70, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
930 AM MST WED AUG 13 2003

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM...CURRENTLY IN CENTRAL
TEXAS...WILL ROTATE UNDER THE HIGH CENTER AND BRING AN INCREASE IN
THUNDERSTORMS TODAY THROUGH FRIDAY. THIS WILL ALSO SERVE TO COOL
THINGS DOWN BACK TO NEAR OR BELOW NORMAL SEASONAL VALUES.

.DISCUSSION...CHANGES ARE A BREWING IN WHICH THE LACK LUSTER MONSOON
THIS MONTH WILL HEAT UP AGAIN OVER THE NEXT SEVERAL DAYS. UPPER AIR
PLOTS AND WATER VAPOR IMAGERY THIS MORNING SHOWED UPPER RIDGE AXIS
EXTENDING SE-NE FROM NORTHERN BAJA TO COLORADO TO MINNESOTA...UPPER
TROF OFF PACIFIC NORTHWEST...CLOSED UPPER LOW SOUTHWEST OF CABO SAN
LUCAS (AROUND 20N/115W)...AND STRONG CLOSED LOW OVER CENTRAL TEXAS.
EMBEDDED IN THE FLOW BETWEEN THE TEXAS LOW AND THE RIDGE AXIS...ARE
SEVERAL DISTURBANCES (ONE OF WHICH IS IN EASTERN COLORADO) WHICH
WILL HELP FOCUS CONVECTION LATER THIS AFTERNOON AND ESPECIALLY
TONIGHT. WATER VAPOR ALSO SHOWING SUBSTANTIAL SUBSIDENCE AREA ON THE
WESTERN FLANK OF TEXAS LOW...WHICH THE WESTERN EDGE MOVING CLOSER TO
THE AZ/NM BORDER. FLOW ALOFT HAS INCREASED OUT OF THE NORTHEAST IN
ADVANCE OF THIS UPPER LOW...THUS GIVING STORMS THAT FIRE OFF THE
HIGHER TERRAIN...ESPECIALLY THE RIM COUNTY...PLENTY OF UMPH TO
MIGRATE DOWN ACROSS THE EASTERN VALLEYS THIS EVENING AND INTO THE
LOW DESERTS TONIGHT. PROBABLY WILL HAVE PLENTY OF DEBRIS CLOUDINESS
AND LIGHT SHOWERS OVERNIGHT ALSO. MAIN THREAT FROM STORMS WILL BE
DAMAGING DOWNBURST WINDS...DUE TO LOW LEVELS STILL ON THE DRY SIDE
GIVING INVERTED V PROFILES...AND LOCALIZED HEAVY RAINFALL. IN THE
SHORTTERM...DEBRIS CLOUD MID-LEVEL DECK ACROSS THE AREA SLOWLY
DECREASING...WHICH WILL DELAY ONSET ON CONVECTION A COUPLE OF HOURS
THIS AFTERNOON. KEMX RADAR WAS STILL SHOWING AN ISOLATED WEAK SHOWER
OVER NORTHWEST COCHISE COUNTY...DRIFTING SOUTHWEST AROUND 20 MPH (A
POSSIBLE CLUE FOR STORM MOTION LATER TODAY).

THE TEXAS UPPER LOW WILL BE IN NORTHERN CHIHUAHUA THURSDAY...KEEPING
THE AREA IN NORTHEAST FLOW ALOFT...THUS ANOTHER ROUND OF RIM COUNTRY
STORMS MIGRATING INTO THE LOWER DESERTS. SEVERE WEATHER AND FLASH
FLOODING LOOK TO BE THE THREATS ON THURSDAY AS ATMOSPHERE WILL
LIKELY BE MORE UNSTABLE WITH 500 MB TEMPERATURES DOWN TO -10C. BY
FRIDAY...THIS UPPER LOW WILL BE OVER SOUTHEAST ARIZONA...KINDA
UNUSUAL THIS TIME OF YEAR...WITH COLD CORE (-10C TO -11C 500 MB AIR)
OVER THE AREA. AT THIS TIME...LIKELY HAVE WETTED UP THE ATMOSPHERE
ENOUGH THAT FLASH FLOODING WILL BE MAIN CONCERN ON FRIDAY. HOPEFULLY
EVERYTHING WILL PLAY OUT CAUSE WE DEFINITELY NEED THE RAINFALL.
TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL AGAIN TODAY...BUT THEN
FALL BELOW NORMAL ON THURSDAY AND FRIDAY DUE TO PREVIOUS NIGHT
CONVECTION...MORE CLOUD COVER AND RAINFALL. ALL OF THIS HANDLED
NICELY IN THE CURRENT ZONE FORECAST PACKAGE.

.TWC...NONE.

AZZ019-029>035-141400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1130 AM MST WED AUG 13 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...THUNDERSTORMS SHOULD FORM ON THE RIM TODAY AND MOVE
SOUTHWEST ACROSS THE AREA THIS EVENING. THE POTENTIAL FOR SEVERE
THUNDERSTORMS IS ABOVE CLIMATOLOGY AND FOR PRECIPITATION IN EXCESS
OF ONE INCH IT IS NEAR CLIMATOLOGY.

DISCUSSION...ALTHOUGH WE HAVE A LOT OF MID LEVEL CLOUDS AND SOME
LIGHT SHOWERS THIS MORNING...NUMERICAL MODELS CONTINUE TO SHOW
THUNDERSTORMS STARTING ALONG THE RIM THIS AFTERNOON AND MOVING
SOUTHWEST ACROSS THE AREA LATE THIS AFTERNOON AND TONIGHT. THE UPPER
LEVEL LOW OVER TEXAS IS CAUSING A NORTHEAST WIND FLOW SO ALL STORMS
WILL MOVE SOUTHWEST AND FAIRLY FAST...15 TO 20 MPH. THIS APPEARS TO
LIMIT THE POTENTIAL FOR HEAVY RAIN BUT THERE IS SOME CONCERN THAT
THE STORMS WILL BE LOADED WITH MOISTURE SINCE MID LEVEL DEW POINT
TEMPERATURES ARE HIGH. SO HAVE LEFT THE CHANCE OF ONE INCH
PRECIPITATION NEAR CLIMATOLOGY EVEN WITH THE ABOVE NORMAL SPEED OF
THE STORMS. MODELS CONTINUE TO SHOW HIGHER THAN NORMAL SEVERE
POTENTIAL...THE LIMITING FACTOR BEING THE MID LEVEL CLOUDS AND THE
INFLUENCE ON SURFACE TEMPERATURES.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

A STRONG IMPULSE WILL SPREAD INTO THE AREA FROM THE EAST THURSDAY
AND THURSDAY NIGHT...WITH A SUBSEQUENT INCREASE IN BOTH THE COVERAGE
OF THUNDERSTORMS AND THE STRENGTH OF SOME STORMS. THE CHANCE FOR
HEAVY RAIN IS EXPECTED TO INCREASE.

.SPOTTER INFORMATION STATEMENT...

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