Flash Flooding and Damaging Wind in Arizona, August 5, 2002

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
205 PM MST MON AUG 5 2002

.SYNOPSIS...A WEATHER DISTURBANCE MOVING NORTH OUT OF MEXICO TODAY
WILL CONTINUE TO IMPACT SOUTHEASTERN ARIZONA THROUGH TUESDAY.
SCATTERED SHOWERS AND THUNDERSTORMS WITH HEAVY DOWNPOURS AND GUSTY
WINDS WILL BE AN ONGOING CONCERN THIS EVENING AND AGAIN TUESDAY.
OTHERWISE...HIGH PRESSURE CENTERED OVER THE CENTRAL UNITED STATES
WILL EVENTUALLY SHIFT WESTWARD AND STRENGTHEN NEAR ARIZONA LATER IN
THE WEEK. THIS WILL RESULT IN WARMER AFTERNOON TEMPERATURES AND A
DIMINISH IN THUNDERSTORM ACTIVITY.

.DISCUSSION...AN INVERTED TROUGH COMBINED WITH MOISTURE AND PLENTY
OF SUNSHINE THIS MORNING HAD GIVEN WAY TO SCATTERED THUNDERSTORMS
THIS AFTERNOON FROM NEAR TUCSON EAST. A MODERATE MID LEVEL EASTERLY
FLOW SHOULD HELP ORGANIZE THUNDERSTORMS AND TRACK THEM WESTWARD
THROUGH THE EARLY EVENING HOURS. OUT WEST ACROSS CENTRAL AND WESTERN
PIMA COUNTY THUNDERSTORM ACTIVITY WILL BE A LITTLE LATE TODAY SINCE
THE MID LEVEL CLOUD DECK CONTINUED TO CUTDOWN ON INSOLATION THERE.
THE FLOW ALOFT WAS ALSO LIGHTER FROM TUCSON WEST WHICH WILL POSE
MORE OF A FLASH FLOOD THREAT THERE LATER THIS EVENING AND TONIGHT.
OTHERWISE...HEAVY RAINFALL AND STRONG T-STORM WINDS WILL BE A
CONCERN THE REST OF THIS AFTERNOON AND EVENING MOST AREAS FROM
TUCSON EAST. THE INVERTED TROUGH SHEERS OUT AND LIFTS NORTH TONIGHT
THROUGH EASTERN ARIZONA AND WESTERN NEW MEXICO. ON TUESDAY THIS
TROUGH IS FORECAST TO STRETCH FROM NORTHEAST ARIZONA THROUGH CENTRAL
NEW MEXICO. UPPER FLOW ON THE BACK SIDE BECOMES MORE DIFLUENT OVER
SOUTHERN ARIZONA BY TUESDAY EVENING AND NIGHT. THIS SHOULD PROVIDE
THE UPPER LEVEL SUPPORT FOR ANOTHER ROUND OF STRONG THUNDERSTORMS
TOMORROW. OTHERWISE...HIGH PRESSURE CENTERED OVER THE CENTRAL UNITED
STATES THE PAST SEVERAL DAYS FLATTENS AS THE WEST COAST TROUGH LIFTS
NORTHEAST. THIS ALLOWS THE HIGH TO SHIFT WESTWARD AND POSITION ITS
SELF AROUND ARIZONA LATER THIS WEEK. LATEST MEDIUM RANGE MODELS
STRENGTHEN THIS RIDGE OVER THE REGION BY THE END OF THIS COMING
WEEKEND. AS A RESULT...DAYTIME HIGHS WILL BE ON A GRADUAL INCREASE
AND MOISTURE ON THE DECREASE FOR LESS THUNDERSTORM ACTIVITY BY NEXT
MONDAY.

.TWC...NONE.

AZZ019-029>035-060700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1155 AM MST MON AUG 5 2002

.SYNOPSIS...A VERY MOIST AIRMASS REMAINS OVER ARIZONA FOR ANOTHER
ROUND OF AFTERNOON AND EVENING THUNDERSTORMS...WITH ISOLATED AREAS
OF EXCESSIVE RAINFALL AND FLASH FLOODING.  THE LARGEST THREAT OF
SEVERE DOWNBURST WINDS IS OVER THE EASTERN HALF OF THE FORECAST AREA.

.DISCUSSION...SKIES CLEARED OVER THE EASTERN HALF OF THE FORECAST
AREA THIS MORNING...ALLOWING FOR BETTER INSOLATION AND THE
DEVELOPMENT OF A DEEPER BOUNDARY LAYER.  THIS WILL LEAD TO
POTENTIALLY STRONGER DOWNDRAFTS FROM ABOUT THE TUCSON METRO AREA
EASTWARD THROUGH GRAHAM AND COCHISE COUNTIES THIS AFTERNOON.
ADDITIONALLY...THE APPROACH OF AN INVERTED TROUGH HAS HELPED TO
ORGANIZED THE EASTERLY FLOW AT MID LEVELS OF THE TROPOSPHERE...WHICH
SHOULD HELP TO ORGANIZE CONVECTION AND MOVE IT WESTWARD DURING THE
AFTERNOON AND EARLY EVENING HOURS.  ORGANIZATION MAY ALSO BE AIDED
BY DIFFERENTIAL HEATING ACROSS CLOUD BOUNDARY.  WILL THEREFORE
INCREASE THE PROBABILITY OF SEVERE DOWNBURST WINDS OVER EASTERN
SECTIONS OF FORECAST AREA.

TO THE WEST...RATHER THICK CLOUD COVER AND LESS ORGANIZATION TO THE
WIND FIELD WILL MAKE FOR SLOW MOVING AND LATER DEVELOPING STORMS IN
CENTRAL AND WESTERN PIMA COUNTY.  THESE STORMS WILL HAVE THE
POTENTIAL FOR VERY HEAVY RAINFALL...WELL IN EXCESS OF 1 INCH IN
ISOLATED LOCATIONS.

STORM MOTION OVER EASTERN SECTIONS WILL BE TO THE WEST AT 15
MPH...AND TO THE NORTH AT 5 OVER EASTERN SECTIONS OF THE FORECAST
AREA.

DRB