Flash Flood in Arizona, August 27, 2003

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
133 PM MST WED AUG 27 2003

.SYNOPSIS...ABUNDANT MOISTURE ALONG WITH AN UPPER LEVEL DISTURBANCE
TO THE EAST WILL PROVIDE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS THROUGH THIS EVENING. SOME OF THE STRONGER STORMS WILL
LIKELY PRODUCE HEAVY DOWNPOURS THAT COULD LEAD TO RUNOFF
PROBLEMS...ESPECIALLY IN PIMA AND PINAL COUNTIES. OTHERWISE...A
GRADUAL DECREASE IN AREAL COVERAGE OF SHOWERS AND THUNDERSTORMS CAN
BE ANTICIPATED THE REST OF THE WEEK INTO EARLY NEXT WEEK. DAYTIME
TEMPERATURES WILL START WARMING BACK UP TO NEAR OR SLIGHTLY ABOVE
NORMAL READINGS BY THE WEEKEND.

.DISCUSSION...RECENT RADAR IMAGERY WAS SHOWING A LOT OF SMALL
DIAMETER SHOWERS AND THUNDERSTORMS ACROSS SERN AZ THIS AFTERNOON.
HAVE NOT SEEN MUCH ORGANIZATION TO THE STORMS SO FAR TODAY AND DO
NOT ANTICIPATE THEM CLUSTERING MUCH THIS EVENING. THE 12Z MORNING
SOUNDING SHOWED A RATHER LIGHT FLOW ALOFT WITH THE STEERING WINDS
GENERALLY FROM THE SOUTHWEST TO WEST. BASED ON THIS...EXPECT STORMS
THIS EVENING TO BE SOMEWHAT SHORT LIVED AND PULSE TYPE IN NATURE
WITH THE STORM MOTION TOWARD THE NORTHEAST AT LESS THAN 10 MPH.
PWATER VALUES WERE CLOSE TO 2 INCHES WITH TUS RUNNING ABOUT 160
PERCENT OF NORMAL. SO THE BOTTOM LINE WAS THAT ANY GIVEN
STORM...ALTHOUGH LOCALIZED AND SHORT LIVED...COULD PRODUCE HEAVY
DOWNPOURS LEADING TO RUNOFF PROBLEMS. THUS...A FLASH FLOOD WATCH
WILL REMAIN POSTED FOR MOST OF SERN AZ WITH THE EXCEPTION OF OUR FAR
EASTERN ZONES TIL 11 PM MST. THIS WATCH APPEARED TO BE IN GOOD SHAPE
FOR NOW...BUT EARLIER RAINS IN SANTA CRUZ COUNTY COULD LIMIT THE
AMOUNT OF ACTIVITY THERE THIS EVENING. WILL LET THE EVENING SHIFT
MAKE ANY NEEDED ADJUSTMENTS TO THE WATCH. BEYOND TODAY...NHC HAD
IGNACIO AT TROPICAL DEPRESSION LEVELS AND DISSIPATING BY FRIDAY
MORNING OVER THE EASTERN PACIFIC. LATEST MODELS CONTINUED TO SHOW A
SHORTWAVE TROUGH DEVELOPING LATER IN THE WEEK AND MOVING INTO THE
WESTERN STATES. EARLIER RUNS SUGGESTED THAT SOME ADDITIONAL MOISTURE
COULD BE PULLED UP HEAD OF THIS TROUGH BUT HAVE NOW BACKED OFF ON
THAT SCENARIO. OVERALL...WILL STILL CALL FOR A DECREASE IN
THUNDERSTORM ACTIVITY RELATIVE TO YESTERDAY AND TODAY. HIGH
TEMPERATURES SHOULD BE RISING EACH DAY AND BE BACK TO AROUND OR
SLIGHTLY ABOVE NORMAL BY THE WEEKEND.

.TWC...FLASH FLOOD WATCH ZONES 029>031-034 TIL 11 PM MST.

AZZ019-029>035-281400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1155 AM MST WED AUG 27 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...TROPICAL DEPRESSION IGNACIO CENTERED NEAR THE BAJA SPUR
WILL CONTINUE TO PUMP MOISTURE INTO SOUTHEAST ARIZONA AS THE SYSTEM
MOVES SLOWLY NORTHWEST UP THE BAJA COAST. AN UPPER LEVEL INVERTED
TROUGH ACROSS FAR WEST TEXAS AND NEW MEXICO WILL ALSO SHIFT SLOWLY
WESTWARD INTO THE REGION TONIGHT. THE COMBINATION OF THESE
FACTORS...AS WELL AS AN UNSTABLE AIRMASS...WILL BRING ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND TONIGHT. HEAVY RAIN
WILL AGAIN BE THE MAIN THREAT. THUS...A FLASH FLOOD WATCH CONTINUES
FOR A PORTION OF SOUTHEAST ARIZONA THROUGH 11 PM MST TONIGHT.

DISCUSSION...ABUNDANT MOISTURE CONTINUES IN PLACE...WITH AREA RAOBS
AND GOES PWAT IMAGERY INDICATING 1.4 TO 2.3 INCHES OF PRECIPITABLE
WATER ACROSS THE FORECAST AREA. MORNING SOUNDINGS ALSO INDICATE
MODERATE INSTABILITY VALUES...WITH AN UNMODIFIED LIFTED INDEX OF
MINUS 4.8 AND A POSITIVE ENERGY VALUE OF 2415 J/KG. IN ADDITION...
TROPICAL DEPRESSION IGNACIO CENTERED JUST SOUTH OF THE BAJA SPUR
CONTINUES TO MOVE VERY SLOWLY TO THE NORTHWEST...WITH ABUNDANT
MOISTURE CONTINUING NORTHWARD ACROSS MEXICO AND INTO SOUTHERN
ARIZONA. AN INVERTED TROUGH TO OUR EAST IS ALSO FORECASTED TO MOVE
WEST INTO ARIZONA THIS AFTERNOON AND EVENING. ALTHOUGH THIS FEATURE
IS FORECASTED TO WEAKEN AS IT PUSHES WEST...IT WILL STILL BRING SOME
WEAK UPPER LEVEL DYNAMICS WITH STRETCHING AND DEFORMATION IN THE
UPPER WIND FIELDS AHEAD OF THIS FEATURE.

THE COMBINATION OF THESE FACTORS WILL BRING THE CHANCE OF SHOWERS
AND THUNDERSTORMS TO SOUTHEAST ARIZONA THIS AFTERNOON AND TONIGHT...
WITH THE MAIN THREAT BEING HEAVY RAINS THAT MAY LEAD TO FLASH
FLOODING. THERE WILL ALSO BE A MINIMAL RISK FOR SEVERE WEATHER
ACROSS THE AREA MAINLY DURING THE AFTERNOON HOURS. THEREFORE...THE
CHANCE OF SEVERE THUNDERSTORMS WILL BE SLIGHTLY BELOW CLIMATOLOGY
TODAY AND TONIGHT. HOWEVER...THE CHANCE FOR GREATER THAN ONE INCH OF
RAINFALL TODAY AND TONIGHT WILL BE ABOVE CLIMATOLOGY...ESPECIALLY
WEST OF A LINE FROM SIERRA VISTA...TO MAMMOTH...TO WINKELMAN. WITH
WEAK MID/UPPER LEVEL FLOW...THE STORMS WILL SHOW LITTLE MOVEMENT
TODAY...WITH NORTHEAST BEING THE FAVORED DIRECTION AT AROUND 5 MPH.

A FLASH FLOOD WATCH IS IN EFFECT THROUGH 11 PM MST TONIGHT FOR THE
FOLLOWING LOCATIONS...SANTA CRUZ...SOUTHERN PINAL AND PIMA COUNTIES.
THE WATCH INCLUDES THE FOLLOWING CITIES...GREEN VALLEY...MARANA...
NOGALES...ORO VALLEY...SELLS...ORACLE...AJO AND THE TUCSON METRO
AREA.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

DRIER AIR WILL BEGIN TO FILTER INTO THE REGION FROM THE WEST AS A
SOUTHWEST FLOW ALOFT BEGINS TO DEVELOP ALONG THE WEST COAST AND PUSH
EASTWARD. AS A RESULT...THE PROSPECT FOR RAIN CHANCES WILL DECREASE
A LITTLE EACH DAY. HOWEVER...SCATTERED SHOWERS AND THUNDERSTORMS ARE
STILL EXPECTED ACROSS EASTERN PORTIONS OF SOUTHERN ARIZONA IN THE
THURSDAY THROUGH TUESDAY TIME FRAME...WHILE ISOLATED THUNDERSTORMS
ARE EXPECTED OVER WESTERN PORTIONS OF SOUTHERN ARIZONA.

.SPOTTER INFORMATION STATEMENT...

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

FOR MORE INFORMATION...SEE THE LATEST WEATHER BULLETINS:
                                AWIPS ID        WMO ID
FLASH FLOOD WATCH               PHXFFATWC       WGUS65 KTWC

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