Flood in Arizona, August 29, 2001

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
910 AM MST WED AUG 29 2001

.SYNOPSIS...MOISTURE HAS INCREASED ACROSS THE REGION OVERNIGHT WITH
THE HIGHEST AMOUNTS JUST SOUTH OF FLAGSTAFF. AN UPPER LEVEL SYSTEM
MOVING THROUGH NORTHERN ARIZONA WILL INTERACT WITH THIS MOISTURE
PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS OVER MOST OF THE AREA.
SOME OF THE STORMS MAY PRODUCE HEAVY RAIN AND STRONG WINDS. DRIER
AIR WILL SLOWLY MOVE INTO THE STATE BY THURSDAY AND FRIDAY...WITH
SHOWERS AND THUNDERSTORMS DECREASING BY THE WEEKEND.

.DISCUSSION...MANY DIFFERENT FACTORS WILL ALL INTERACT TO PRODUCE A
FAIRLY ACTIVE DAY TODAY. THE FIRST IS THAT MOISTURE HAS INCREASED TO
NEAR SEASONAL VALUES THIS MORNING...THE RESULT OF CONTINUED MCS
ACTIVITY SOUTH OF THE BORDER FOR THE LAST SEVERAL NIGHTS. THIS HAS
ALSO SPAWNED A SIGNIFICANT GULF SURGE...WITH A 30KT LOW-LEVEL JET
STREAMING THROUGH YUMA ALL MORNING. IN CONJUNCTION WITH THIS...A
SPEED MAX AT 300 MB WILL MOVE THROUGH THE SOUTHWEST TODAY.
CONVECTION HAS BEEN OCCURRING ALL NIGHT ALONG THE SHEAR AXIS...AND
EXPECT UPPER LEVEL DIV TO INCREASE OVER CENTRAL ARIZONA BY THE
AFTERNOON. IN ADDITION...A WEAK TROUGH OVER THE NORTHERN GREAT BASIN
WILL FURTHER INCREASE MOISTURE THROUGH THE DAY. 700 MB FLOW FROM THE
SOUTHWEST WILL APPROACH 20 KTS...WITH RELATIVELY LIGHT FLOW OVER THE
NORTHEASTERN PORTIONS OF THE STATE. THIS WILL SET UP A LOW-LEVEL
CONVERGENCE ZONE ALONG THE RIM AND INTO THE WHITE MOUNTAINS. A WEAK
CIRCULATION FROM LAST NIGHTS CONVECTION OVER THE LCR WILL ALSO HAVE
TO BE WATCHED AS A POSSIBLE FOCUSING MECHANISM LATER THIS MORNING.
ALL THIS MEANS IS THAT SCATTERED THUNDERSTORMS ARE LIKELY TODAY IN
JUST ABOUT EVERY ZONE. THE SPEED MAX ALOFT COULD AID IN THE
DEVELOPMENT OF ISOLATED SEVERE STORMS. MOISTURE WILL SLOWLY DECREASE
THROUGH THE REMAINDER OF THE WEEK. THESE TRENDS ARE COVERED IN THE
CURRENT ZONE PACKAGE...ONLY ZONE THAT MAY NEED TO BE RAISED IS
YAVAPAI COUNTY. DUE TO THE DRIER AIR ALOFT OVER YAVAPAI...WILL WAIT
AND SEE BEFORE UPDATING. NO ZONE UPDATES NEEDED AT THIS TIME.
PETERSON.

.FGZ...NONE.

AZZ004>018-037>040-291930-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
930 AM MST WED AUG 29 2001

...SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED OVER MUCH OF
NORTHERN AND CENTRAL ARIZONA TODAY...

MOISTURE HAS INCREASED SIGNIFICANTLY ACROSS THE REGION OVERNIGHT. IN
ADDITION...A DISTURBANCE IN THE UPPER LEVELS OF THE ATMOSPHERE WILL
AID IN THE DEVELOPMENT OF THUNDERSTORMS TODAY. EXPECT SHOWER AND
THUNDERSTORM ACTIVITY TO INCREASE INTO THE AFTERNOON HOURS...WITH
SOME STORMS NEARING SEVERE LEVELS. THE BEST CHANCE FOR ORGANIZED
STORM DEVELOPMENT WILL BE TO THE EAST AND SOUTHEAST OF FLAGSTAFF
WHERE DEEPER MOISTURE AND MORE INSTABILITY EXISTS. STORMS TO THE
EAST AND SOUTHEAST OF FLAGSTAFF HAVE THE POTENTIAL TO PRODUCE UP TO
3 INCHES OF RAIN...ALONG WITH DANGEROUS WINDS AND HAIL. ISOLATED
STRONGER STORMS ARE POSSIBLE ELSEWHERE...BUT ARE MOST LIKELY EAST
OF FLAGSTAFF. EXPECT STORM ACTIVITY TO PERSIST INTO THE EVENING
HOURS...BEFORE DECREASING BY MIDNIGHT.

THOSE WITH OUTDOOR INTERESTS TODAY...INCLUDING HIKING...AND
CAMPING...SHOULD BE AWARE OF THE THREAT FOR SLOT CANYON FLOODING.
RAINFALL IS ALREADY OCCURRING WEST OF PAGE...AND SCATTERED
THUNDERSTORMS WILL CONTINUE TO DEVELOP OVER THE CANYON COUNTRY
BETWEEN FLAGSTAFF AND PAGE ALL AFTERNOON. WITH THE INCREASED
MOISTURE ACROSS THE AREA...THESE STORMS CAN DROP OVER AN INCH OF
RAIN IN A SHORT PERIOD OF TIME. THIS IS ALL THAT IS NEEDED TO
PRODUCE LOCALIZED...BUT RAPID RISES IN SLOT CANYONS AND OTHER DRY
WASHES.