Flash Flood Warning 50, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
140 PM MST FRI AUG 22 2003

.SYNOPSIS...HIGH PRESSURE OVER THE CENTRAL AND SOUTHERN ROCKIES
WILL MAINTAIN A FAVORABLE MOIST FLOW FOR SCATTERED SHOWERS AND
THUNDERSTORMS INTO MID NEXT WEEK. IMPULSES IN THE SOUTHERLY AND
EASTERLY FLOW WILL ENHANCE THUNDERSTORMS FROM TIME TO TIME. HIGH
TEMPERATURES WILL BE NEAR OR SLIGHTLY ABOVE NORMAL THE NEXT SEVERAL
DAYS.

.DISCUSSION...MORNING SHOWERS HAD DELAYED THE REDEVELOPMENT ACROSS
THE AREA THIS AFTERNOON...BUT STILL EXPECT THUNDERSTORMS TO FORM BY
THIS EVENING. DRIER AIR ADVECTING INTO FAR SOUTHEAST AZ WILL KEEP
THE ACTIVITY LIMITED THERE...BUT THE REST OF OUR CWA SHOULD SEE A
DECENT AMOUNT THIS EVENING. THE DEEPEST MOISTURE WAS POSITIONED OVER
WESTERN AND CENTRAL ARIZONA WITH THE WESTERN EDGE RIGHT ALL THE CO
RIVER VALLEY. THE WESTERN EDGE OF THIS MOISTURE AXIS HAD SEEN MOST
OF THE THUNDERSTORMS SO FAR TODAY WITH CELLS TRACKING NORTHWARD AND
NEW ONES DEVELOPING ON THE SOUTHERN FLANK. WESTERN SECTIONS OF OUR
CWA WILL LIKELY SEE A SIMILAR SCENARIO LATER TODAY WITH CELLS
TRAINING OVER THE SAME GENERAL AREA...AND SUBSEQUENTLY LEADING TO A
FLASH FLOOD THREAT. FOR NOW...DO NOT HAVE A HIGH DEGREE OF
CONFIDENCE THAT WIDESPREAD FLOODING WILL BE ENOUGH OF A PROBLEM TO
WARRANT A FLASH FLOOD WATCH. HOWEVER...WILL BE WATCHING WESTERN AND
CENTRAL PIMA COUNTY CLOSELY THIS EVENING. AN INVERTED TROUGH
STRETCHING OVER NORTHERN MEXICO THROUGH WEST TEXAS WAS STILL
ANTICIPATED TO PROVIDE SOME UPPER LEVEL FORCING ON THE LARGE SCALE
LATER TODAY INTO SATURDAY. ALTHOUGH A FEW MODELS INDICATED A
SIGNIFICANT AMOUNT OF DRYING FROM THE EAST ACROSS GRAHAM AND COCHISE
COUNTIES BY TOMORROW. IF THIS HAPPENS...THE INVERTED TROUGH WILL NOT
DO MUCH FOR THE THUNDERSTORM CHANCES OUT EAST. BEYOND THE REST OF
TODAY AND SATURDAY...THE GENERAL FLOW PATTERN WAS PROGGED TO REMAIN
FAVORABLE FOR TYPICAL SHOWERS AND THUNDERSTORMS. HIGH TEMPERATURES
WERE ALSO PROGGED TO BE AROUND OR SLIGHTLY ABOVE CLIMO WHICH LOOKS
REASONABLE BASED ON PRECIP CHANCES AND PROGGED HEIGHTS.

.TWC...NONE.

AZZ019-029>035-231400-

HAZARDOUS WEATHER OUTLOOK...CORRECTION TO DATE
NATIONAL WEATHER SERVICE TUCSON AZ
1203 PM MST FRI AUG 22 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...THE PROBABILITY OF RECEIVING PRECIPITATION IN EXCESS OF
ONE INCH WILL BE ABOVE CLIMATOLOGY ACROSS THE WESTERN DESERTS TODAY
AS HIGHER MOISTURE AND A FAVORABLE FLOW ALOFT RESIDES IN THIS AREA.
IN FAR SOUTHEAST ARIZONA...MAINLY ALONG A LINE FROM SAFFORD TO
DOUGLAS...A DRIER LOW LEVEL ATMOSPHERE WILL INCREASE THE THREAT FOR
DAMAGING THUNDERSTORM OUTFLOW WINDS BUT A LOWER POSSIBILITY TO
RECEIVE VERY HEAVY PRECIPITATION.

DISCUSSION...ALTHOUGH THE 12Z UPPER AIR SOUNDING WAS CONTAMINATED BY
THE SHOWERS THAT PERSISTED ACROSS SOUTH CENTRAL ARIZONA EARLIER THIS
MORNING... IT STILL INDICATED AN UNSTABLE ATMOSPHERE WITH UNMODIFIED
LIFTED INDEX AND CAPE VALUE OF -3.9 AND 1656 J/KG RESPECTIVELY. THE
AREA WILL NOT REALIZE THE FULL EXTENT OF THIS AIRMASS EAST OF TUCSON
AS DRIER AIR IN THE LOW TO MID LEVELS NUDGES THE BORDER WITH NEW
MEXICO AND WARMER AIR ALOFT WILL ADVECT INTO THE FAR EAST. CURRENT
WATER VAPOR IMAGERY INDICATED A DRY POCKET OF AIR ACROSS SOUTHWEST
NEW MEXICO THIS MORNING...WHICH WILL PUSH SLOWLY TO THE WEST TODAY.
WILL LIKELY SEE THUNDERSTORMS DEVELOP ALONG THE MOISTURE BOUNDARY
THIS AFTERNOON...MAINLY ALONG A LINE FROM SAFFORD TO DOUGLAS...AND
PUSH TOWARDS THE WEST NORTHWEST AT 15 MPH. THE STORMS THAT DEVELOP
OUT EAST WILL HAVE A BETTER THREAT TO PRODUCE DAMAGING THUNDERSTORM
OUTFLOW WINDS AND A LOWER POSSIBILITY TO RECEIVE PRECIPITATION IN
EXCESS OF ONE INCH AS THE DRIER LOW LEVELS WILL AID EVAPORATION.
THESE STORMS WILL INCREASE IN THEIR ABILITY TO PRODUCE HEAVIER
PRECIPITATION AS THEY MOVE...OR DEVELOP FURTHER WEST IN A MORE MOIST
AIRMASS AND AN AREA WHERE AN UPPER LEVEL STRETCHING DEFORMATION
EXISTS.

FURTHER WEST...THE GOES-10 PRECIPITABLE WATER IMAGERY INDICATED THAT
A SIGNIFICANT AMOUNT OF LOW AND MID LEVEL MOISTURE EXISTS ACROSS THE
DESERTS IN SOUTHWEST ARIZONA. THIS AREA WILL REALIZE STRONGER
THUNDERSTORM DEVELOPMENT WITH AN ABOVE CLIMATOLOGICAL PROBABILITY OF
PRODUCING PRECIPITATION IN EXCESS OF ONE INCH. THIS IS DUE TO THE
FACT THAT THIS AREA NOT ONLY HAS THE MOISTURE...BUT ALSO EXISTS
WITHIN THIS SAME STRETCHING DEFORMATION.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

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