Flash Flood Warning 35, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
910 PM MST WED AUG 1 2007

.SYNOPSIS...A VERY MOIST AIR MASS OVER THE REGION AND WEAK
DISTURBANCES EMBEDDED IN THE FLOW ALOFT WILL MAKE FOR A FEW MORE
ACTIVE THUNDERSTORM DAYS. AS MOISTURE LEVELS REMAIN HIGH...THE
THREAT FOR HEAVY RAINFALL AND RUNOFF PROBLEMS WILL CONTINUE. A LOW
PRESSURE TROUGH DEEPENING ALONG THE WEST COAST MAY SPREAD DRIER AIR
INTO THE REGION NEXT WEEK FOR A DECREASE IN THUNDERSTORM CHANCES.

&&
.DISCUSSION...THE LATEST WATER VAPOR IMAGERY INDICATED THAT THE
UPPER HIGH CENTER WAS LOCATED OVER SOUTHERN NEW MEXICO AND WEST
TEXAS THIS EVENING. THE UPPER DIFFLUENT AREA ON THE PERIPHERY OF THIS
HIGH CONTINUES TO MOVE AROUND THE PERIPHERY OF THIS UPPER HIGH INTO
SOUTHEAST ARIZONA...AND WILL CONTINUE TO DEVELOP THUNDERSTORMS
CAPABLE OF PRODUCING VERY HEAVY RAINFALL. ALTHOUGH THE MASS OF
STORMS WILL MOVE WEST NORTHWEST ACROSS THE FORECAST AREA...THE
INDIVIDUAL STORMS CONTINUE TO MOVE EAST BACK OVER THE AREAS THAT
RECEIVED RAINFALL. THEREFORE...FLASH FLOOD THREAT STILL HIGH ACROSS
THE ENTIRE FORECAST AREA THIS EVENING. THESE STORMS ARE CAPABLE OF
PRODUCING UP TO AN INCH OF RAINFALL IN A SHORT PERIOD OF TIME...WITH
ISOLATED LOCATIONS RECEIVING 2.00 INCHES.

&&

.PREV DISCUSSION...THUNDERSTORMS HAVE BEEN SLOW TO GET STARTED TO
TODAY AS THE CAP ALOFT SEEMS TO HAVE STRENGTHENED. A FEW TOWERING CU
HAVE POPPED THE CAP TO THE EAST AND WEST OF THE TUCSON METRO AREA
AND BECOME THUNDERSTORMS...BUT THEY HAVE BEEN SHORT LIVED. AS THE
AFTERNOON PROGRESSES THE CAP/S STRENGTH SHOULD DIMINISH RESULTING IN
SCATTERED THUNDERSTORMS ACROSS SOUTHEASTERN ARIZONA. AND SINCE THE
FLOW IN THE LOWER AND MID ATMOSPHERE IS WEAK...HEAVY RAIN LEADING TO
FLASH FLOODING IS THE MAIN CONCERN.

AT 130 PM MST SATELLITE IMAGERY INDICATED THE DISTURBANCE SOUTH OF
NEW MEXICO IS TRACKING TO THE NORTH AS THE NAM AND GFS MODELS
FORECAST...HOWEVER IT IS FURTHER WEST. SINCE IT IS CLOSER TO ARIZONA
ITS INFLUENCE MAY BE FELT IN COCHISE COUNTY LATER THIS EVENING AND
BEARS WATCHING.

DEEP MOISTURE WILL REMAIN IN PLACE OVER SOUTHERN ARIZONA FOR THE
NEXT SEVERAL DAYS ALONG WITH WEAK DISTURBANCES SKIRTING THE AREA FOR
CONTINUED MAINLY AFTERNOON AND EVENING THUNDERSTORMS. THE NEXT
SYNOPTIC SCALE FEATURE TO AFFECT OUR WEATHER WILL BE AN INVERTED
TROUGH/EASTERLY WAVE. THIS WAVE IS FORECAST TO MOVE ACROSS SOUTHERN
CHIHUAHUA AND SOUTHERN SONORA...MEXICO FRIDAY AND SATURDAY AS A
TROUGH OF LOW PRESSURE DIGS ALONG THE WEST COAST. THE GFS THEN
FORECASTS THE WAVE TO GET CAUGHT IN THE SOUTHWEST FLOW OF THE TROUGH
AND EVENTUALLY MOVES IT ACROSS ARIZONA ON MONDAY AND TUESDAY. AFTER
DYNAMICAL FORCING PUSHES THROUGH THE AREA THE SOUTHWESTERLY FLOW
WILL BRING DRIER AIR INTO THE REGION MIDWEEK. THEREFORE...A TREND
FOR LOWER CHANCES OF SHOWERS AND THUNDERSTORMS WILL BEGIN ON TUESDAY.

&&

.AVIATION...ANY TSTM COULD BRING VISIBILITIES BRIEFLY TO IFR...CIGS
TO MVFR...AND GUSTS TO 40KTS. EXPECTING DEBRIS 120-150 CLOUD DECKS
OVERNIGHT...BUT IF THAT DOES NOT HAPPEN...WE COULD AGAIN SEE PATCHY
LOW CLOUDS/FOG AROUND SUNRISE. HAVE NOT CARRIED THAT IN TAFS OR
TWEBS AT THIS TIME SINCE CONFIDENCE IS TOO LOW. AVIATION DISCUSSION
NOT UPDATED FOR TAF AND TWEB AMENDMENTS.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

WEATHER.GOV/TUCSON

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1047 AM MST WED AUG 1 2007

AZZ019-029>035-020700-
NORTHERN GREENLEE COUNTY-SOUTHEAST PINAL COUNTY-
UPPER GILA RIVER VALLEY-WESTERN PIMA COUNTY-TOHONO OODHAM NATION-
TUCSON METRO/MARANA/GREEN VALLEY-SANTA CRUZ COUNTY-COCHISE COUNTY-
1047 AM MST WED AUG 1 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
ARIZONA AND SOUTHEAST ARIZONA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A RISK OF STRONG THUNDERSTORMS ONCE AGAIN THIS AFTERNOON
AND EVENING...WITH HEAVY RAIN AND ISOLATED FLASH FLOODING THE MAIN
CONCERNS. INITIALLY...THUNDERSTORMS WILL TEND TO REMAIN NEAR MOUNTAINS
EARLY THIS AFTERNOON BECAUSE STEERING WINDS WERE VERY LIGHT.
HOWEVER COMPUTER MODELS FORECAST MID LEVEL WINDS TO INCREASE A BIT
THIS AFTERNOON...WHICH WILL TEND TO PUSH STORMS SLOWLY TO THE WEST
OR NORTHWEST. A WEAK UPPER LEVEL DISTURBANCE OVER NORTHWEST
CHIHUAHUA WAS ALSO MOVING TOWARD COCHISE COUNTY...AND MAY ENHANCE
DEVELOPMENT LATE THIS AFTERNOON AND THIS EVENING ACROSS MUCH OF
SOUTHEAST ARIZONA.

BECAUSE OF THE WIDESPREAD HEAVY RAINS YESTERDAY...THE ATMOSPHERE
WILL TAKE LONGER TO DESTABILIZE TODAY. THUS IT MAY TAKE LONGER FOR
THUNDERSTORMS TO SPREAD INTO THE VALLEYS AND DESERTS COMPARED TO
YESTERDAY. HOWEVER ONCE THEY DO...THEY WILL AGAIN HAVE A TENDENCY
TO CLUSTER AND MERGE...WHILE PRODUCING RAINFALL RATES OF 1 TO 2
INCHES PER HOUR AND PERHAPS ISOLATED WIND GUSTS TO 50 MPH. IF THE
THUNDERSTORMS BECOME MORE ORGANIZED...FLASH FLOOD WATCHES MAY NEED
TO BE ISSUED. REGARDLESS IF THE THEY BECOME ORGANIZED OR NOT...ANY
SIGNIFICANT RAIN ON SATURATED SOILS OVER SOUTHEAST ARIZONA WILL
LIKELY CAUSE RUNOFF PROBLEMS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE RISK OF STRONG THUNDERSTORMS WITH HEAVY RAIN WILL CONTINUE
FOR SEVERAL MORE DAYS...ALTHOUGH ACTIVITY MAY BE A BIT LESS
WIDESPREAD THURSDAY. INITIALLY IT APPEARED THAT THE RISK OF
THUNDERSTORMS WOULD DIMINISH LATE IN THE WEEK...BUT A NEW UPPER
LEVEL DISTURBANCE IS NOW FORECAST TO DEVELOP OVER NORTHERN MEXICO
AND MOVE WEST TOWARD THE REGION BY FRIDAY OR SATURDAY. THIS WILL
BE MONITORED CLOSELY SINCE ANY ADDITIONAL RAINS OVER THE NEXT
SEVERAL DAYS COULD ONCE AGAIN INCREASE THE RISK OF FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

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

PYTLAK