Flood in Arizona, August 11, 2001

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
230 PM MST SAT AUG 11 2001

.SYNOPSIS...A MOIST AND UNSTABLE AIR MASS WILL HELP PRODUCE SHOWERS
AND THUNDERSTORMS OVER NORTHERN ARIZONA THROUGH THE REMAINDER OF THE
WEEKEND AND INTO THE FIRST PART OF NEXT WEEK. A FEW THUNDERSTORMS
MAY PRODUCING HEAVY RAIN...MAINLY ALONG AND SOUTH OF A LINE FROM ST.
JOHNS TO PAYSON LATE THIS AFTERNOON AND EVENING.

.DISCUSSION...PRECIPITABLE WATER IN THE 1.25 TO 1.5 INCH RANGE OVER
THE SOUTHERN AND SOUTHEAST PORTIONS OF THE FORECAST AREA THIS
AFTERNOON...WILL GRADUALLY WORK NORTH THROUGH THE OVERNIGHT HOURS
INTO SUNDAY. WEAK FLOW OVER THE EASTERN RIM AND WHITE MOUNTAINS WILL
RESULT IN SLOW MOVING THUNDERSTORMS WITH THE POTENTIAL FOR FLASH
FLOODING THIS AFTERNOON AND EVENING. ALREADY MOIST GROUND...WILL
RESULT IN RAPID RUNOFF...ESPECIALLY IN THE WATCH AREA.

SUNDAY...WITH MOISTURE IN PLACE OVER THE FORECAST AREA...SHOWERS AND
THUNDERSTORM WILL BE MORE WIDE SPREAD ESPECIALLY SOUTH AND EAST OF A
LINE EXTENDING FROM THE NORTHEAST PLATEAUS TO THE BRADSHAW
MOUNTAINS. INERTIAL INSTABILITY AND UPPER LEVEL DIVERGENCE WILL AID
ORGANIZED THUNDERSTORM DEVELOPMENT LATE SUNDAY AFTERNOON INTO THE
OVERNIGHT HOURS MAINLY OVER THE EASTERN MOGOLLON RIM DOWN INTO THE
WHITE MOUNTAINS AND NORTHERN GILA COUNTY.

MONDAY...DEEP MOISTURE LINGERS OVER NORTHERN ARIZONA WITH THE
POSSIBILITY OF A WEAK EASTERLY WAVE...EXPECT ANOTHER ROUND OF SHOWERS
AND THUNDERSTORMS ESPECIALLY SOUTH OF A LINE FROM GRAND CANYON
VILLAGE TO WINDOW ROCK.

EXTENDED...HIGH PRESSURE ALOFT IS FORECAST TO MOVE FARTHER WEST
TUESDAY THROUGH THURSDAY...ALLOWING FOR A LITTLE DRIER AIR IN THE
MID AND UPPER LEVELS...THIS WILL REDUCED THE POTENTIAL FOR HEAVY
RAIN AS WELL AS AREAL COVERAGE OF THE THUNDERSTORMS...WILL KEEP
CHANCE WORDING IN THE ZONES...AS LOW LEVEL MOISTURE WILL LIKELY NOT
BE ERODED AWAY. AVN MODEL AND MRF HAVE BEEN TRYING TO DRY THINGS OUT
IN LATER PERIODS OF THE EXTENDED...AND THIS HAS NOT BEEN THE TREND.

CLEMMONS

.FGZ...FLASH FLOOD WATCH UNTIL 900 PM MST FOR ZNS 014-016>018

AZZ004>018-037>040-101930-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
945 AM MST SAT AUG 11 2001

...SCATTERED THUNDERSTORMS TODAY ACROSS NORTHERN ARIZONA WITH THE
POTENTIAL FOR HEAVY RAINFALL...

A MOIST AND UNSTABLE AIR MASS WILL REMAIN OVER ARIZONA TODAY AND
TONIGHT. AS A RESULT...WIDESPREAD SHOWERS AND THUNDERSTORMS ARE
EXPECTED...ESPECIALLY EAST OF A PAGE TO PRESCOTT LINE. THE MAIN
THREAT FROM THESE STORMS WILL BE HEAVY RAIN...WITH RAINFALL AMOUNTS
OF 1 TO 4 INCHES...AND THE POTENTIAL FOR LOCALIZED FLASH FLOODING.
THE MAIN THREAT OF FLOODING WILL BE LOCATED OVER THE EASTERN
MOGOLLON RIM...NORTHERN GILA COUNTY...EASTERN PORTIONS OF THE
LITTLE COLORADO RIVER VALLEY AND THE WHITE MOUNTAINS. A FEW OF
THUNDERSTORMS THAT DEVELOP ALONG AND TO THE WEST OF THE PAGE TO
PRESCOTT LINE HAVE THE POTENTIAL FOR PRODUCING STRONG OUTFLOW WINDS.