Severe Thunderstorm Warning 73, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
240 PM 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 TONIGHT THROUGH FRIDAY. WEAK DISTURBANCES OUT AHEAD OF
THIS LOW WILL MOVE OUT OF THE CENTRAL ROCKIES AND HELP FOCUS
THUNDERSTORM ACTIVITY OVER THE NEXT SEVERAL DAYS. TEMPERATURES WILL
BE COOLER THAN THE PAST WEEK AND AT OR BELOW SEASONAL NORMALS FOR
MID-AUGUST.

.DISCUSSION...CHANGES ARE A BREWING IN WHICH THE LACK LUSTER MONSOON
THIS MONTH WILL HEAT UP AGAIN...STARTING TONIGHT AND CONTINUING INTO
FRIDAY. UPPER AIR PLOTS AND WATER VAPOR IMAGERY THIS MORNING SHOWED
UPPER RIDGE AXIS EXTENDING SE-NE FROM NORTHERN BAJA TO COLORADO TO
MINNESOTA...AN UPPER TROF OFF THE PACIFIC NORTHWEST...A CLOSED UPPER
LOW SOUTHWEST OF CABO SAN LUCAS (AROUND 21N/117W)...AND A 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 MOVING THRU NW NEW MEXICO AND THE OTHER IS STARTING TO
DEVELOP IN EASTERN NEBRASKA) WHICH WILL HELP FOCUS CONVECTION
TONIGHT. 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. ISOLATED
CONVECTION HAS FIRED ON EITHER SIDE OF THE MID-LEVEL DECK THIS
AFTERNOON WITH A STRONG STORM UP IN THE WHITES. THIS STORM LIKELY
BEING HELPED BY DISTURBANCE IN NW NEW MEXICO...WHICH WILL MOVE
ACROSS THE AREA BETWEEN 8 PM AND MIDNIGHT. THUS EXPECT ACTIVITY TO
PICK UP IN EARNEST AFTER SUNSET.

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 WITH SLOW
MOVING STORMS. HOPEFULLY EVERYTHING WILL PLAY OUT CAUSE WE
DEFINITELY NEED THE RAINFALL. TEMPERATURES THAT WERE SLIGHTLY ABOVE
NORMAL TODAY...WILL THEN FALL BELOW NORMAL ON THURSDAY AND FRIDAY
DUE TO PREVIOUS NIGHT CONVECTION...MORE CLOUD COVER AND RAINFALL.

UPPER LOW TO LIFT OUT OF THE STATE ON SUNDAY WITH UPPER RIDGE
BUILDING BACK IN. EXPECT LESS ACTIVITY EARLY NEXT WEEK THUS HAVE
GONE WITH UNCERTAINTY WORDING.

.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.