Flash Flood Warning 18, NWS Flagstaff, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF
330 PM MST THU OCT 21 2004

.SYNOPSIS...A STRONG PACIFIC STORM AND COLD FRONT WILL CONTINUE TO
MOVE ACROSS THE SOUTHWEST THIS EVENING BRINGING WIDESPREAD HEAVY
RAIN AND MOUNTAIN SNOWS. AHEAD OF THE COLD FRONT...WINDS WILL BE
STRONG AND GUSTY THIS EVENING. SIGNIFICANT RAINFALL IS EXPECTED OVER
PORTIONS OF COCONINO AND YAVAPAI COUNTIES THIS EVENING...AND THERE
IS A THREAT OF FLOODING FROM HEAVY RAINFALL. SNOWFALL ACCUMULATIONS
OF 3 TO 6 INCHES ARE EXPECTED OVER THE HIGHER TERRAIN.

&&

.DISCUSSION...MODERATE RAIN AND SNOW EXPECTED TO CONTINUE WEST OF A
LINE FROM PAGE TO FLAGSTAFF TO BLACK CANYON CITY. REPORTS FROM
WESTERN COCONINO COUNTY AND WESTERN YAVAPAI COUNTY SHOWS THAT ON THE
AVERAGE 2 TO 3 INCHES OF RAIN HAS ALREADY FALLEN WITH SOME AREAS
FROM FRAZIER WELLS SOUTH TO GOODWIN MESA HAVE RECEIVED 3 TO 4
INCHES OF RAIN. A URBAN AND SMALL STREAM FLOOD ADVISORY WAS ISSUED
AT 925 AM MST. ALSO SOME REPORTS OF ROCK SLIDES AND FLOODING IN
PORTIONS OF WESTERN YAVAPAI COUNTY WEST OF PRESCOTT CAME IN EARLIER
TODAY.

THE ETA12 SPEED OF THE PRECIP BAND HAS BEEN DOING FAIRLY WELL...
WHERE AS THE GFS HAS BEEN TOO FAST. AT ANY RATE BOTH MODELS
ACCELERATE THIS SYSTEM TO NORTHEAST OVERNIGHT IN RESPONSE TO THE
UPSTREAM SHORTWAVE ENTERING NORTHERN NEVADA. MAIN CONCERN FOR THE
OVERNIGHT INTO FRIDAY MORNING TIME PERIOD...WILL BE DROPPING SNOW
LEVELS AND THE POSSIBILITY OF APPRECIABLE AMOUNTS OF SNOW ABOVE 6500
FEET...AT LEAST ALONG THE MOGOLLON RIM INTO THE WHITE MOUNTAINS.  IT
APPEARS FROM THE FCST MODELS THAT THE DYNAMICS PRODUCING THE HEAVIER
PRECIP WILL CONTINUE OVER THE AREA THROUGH AT LEAST 10 PM BEFORE
MOVING TO THE EAST OF A PAGE TO FLAGSTAFF TO CANYON CITY LINE.

PER THE LATEST GFS...A STRONG SHORTWAVE IS MOVING INTO SOUTHWEST AZ
THIS AFTERNOON...THIS FEATURE MOVES NORTHWARD OVER THE PRECIP BAND
AT AROUND 00Z. PER 88D RADARS...THE PRESENTS OF THIS VORT FEATURE
HAS ALREADY BEGUN TO ENHANCE PRECIP FROM MARICOPA COUNTY NORTHWARD
TO FLAGSTAFF. THE 700 MB TEMPERATURE GRADIENT ALONG THE COLD FRONT
TIGHTENS DURING THE 00Z TIME STEP. THE TIGHTENING OF THE TEMP FIELD
WILL HELP BRING SNOW LEVELS DOWN FASTER THAN CURRENT MODELS
ADVERTISE. ALSO THE 500-300 MB TEMP ADV MAXS OVER YAVAPAI COUNTY
ALONG WITH THE THE PV-ADVECTION WITHIN THE SAME LAYER. WE ARE
EXPECTING THE PRECIP RATES TO INCREASE DURING A 3 TO 4 HOUR TIME
PERIOD AROUND 00Z AS THIS FEATURE LIFTS NORTH ACROSS THE FRONTAL
BAND. BECAUSE OF THE COOLING AT THIS TIME AND THE INCREASE IN PRECIP
INTENSITY...WE HAVE DECIDED ON A SNOW ADVISORY FOR ZONE
6...15...16...AND 17.
&&

.FGZ WATCHES/WARNINGS/ADVISORIES...FLOOD WATCH THRU 2400 FOR
COCONINO AND YAVAPAI COUNTIES INCLUDING ZONES 004>008-015-018-037.

URBAN AND SMALL STREAM FLOOD ADVISORY THROUGH 445 PM MST INCLUDING
AZ ZONES 004-006>008-037

WIND ADVISORY THRU 2000 ZONES 010>014-040.

SNOW ADVISORY THROUGH 600 AM MST SATURDAY MORNING FOR AZ ZONES
004-006-015-016-017 ABOVE 7500 FEET WHITE MOUNTAINS AND FOR THE REST
6500 FEET.

&&
TC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
630 AM MST THU OCT 21 2004

AZZ004>018-024-037>040-211921-
BLACK MESA AREA-CHINLE VALLEY-CHUSKA MOUNTAINS AND DEFIANCE PLATEAU-
COCONINO PLATEAU-EASTERN MOGOLLON RIM-GRAND CANYON COUNTRY-
KAIBAB PLATEAU-LITTLE COLORADO RIVER IN APACHE COUNTY-
LITTLE COLORADO RIVER VALLEY IN COCONINO COUNTY-
LITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTY-
MARBLE CANYON AND GLEN CANYON-NORTHEAST PLATEAUS AND MESAS-
NORTHEAST PLATEAUS AND MESAS - SOUTH OF HWY 264-NORTHERN GILA-
OAK CREEK AND SYCAMORE CANYONS-SOUTHERN GILA/TONTO NF FOOTHILLS-
WESTERN MOGOLLON RIM INCLUDING FLAGSTAFF-WHITE MOUNTAINS-
YAVAPAI COUNTY MOUNTAINS-YAVAPAI COUNTY VALLEYS AND BASINS-
630 AM MST THU OCT 21 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR APACHE...COCONINO...NORTHERN
GILA...NAVAJO...AND YAVAPAI COUNTIES IN NORTHERN ARIZONA.

.DAY ONE...TODAY

A STRONG AND MOIST PACIFIC STORM SYSTEM AND ASSOCIATED COLD FRONT
WILL CONTINUE TO MOVE ACROSS ARIZONA TODAY. AHEAD OF THE COLD
FRONT...WINDS WILL BECOME STRONG AND GUSTY LATER THIS MORNING AND
CONTINUE UNTIL THIS EVENING. A WIND ADVISORY HAS BEEN ISSUED FOR
PORTIONS OF EASTERN ARIZONA. SEE PRODUCT PHXNPWFGZ FOR ADDITIONAL
INFORMATION.

AREAS OF WIDESPREAD MODERATE-TO-HEAVY RAINFALL ARE EXPECTED TO
DEVELOP THIS MORNING AND CONTINUE UNTIL THIS EVENING AS THE STORM
SYSTEM AND COLD FRONT MOVE ACROSS ARIZONA. RAINFALL AMOUNTS OF 1 TO 3
INCHES...WITH LOCALLY HEAVIER AMOUNTS...ARE EXPECTED ACROSS PORTIONS
OF YAVAPAI AND COCONINO COUNTIES. A FLOOD WATCH CONTINUES FOR THESE
LOCATIONS. SEE PRODUCT PHXFFAFGZ FOR ADDITIONAL INFORMATION.

SNOW LEVELS REMAIN VERY HIGH THIS MORNING BUT ARE EXPECT TO FALL
QUICKLY LATER THIS AFTERNOON AND OVERNIGHT...FINALLY BOTTOMING OUT AT
AROUND 6500 FEET IN THE WESTERN HALF OF ARIZONA...AND AROUND 7500
FEET IN THE EASTERN HALF. BECAUSE OF THE WARM CHARACTER OF THIS
STORM...SNOWFALL AMOUNTS ARE EXPECTED TO REMAIN LIGHT WITH ONLY A FEW
INCHES OVER THE HIGHER TERRAIN...WITH THE LARGEST AMOUNTS EXPECTED
OVER THE KAIBAB PLATEAU AND THE HIGHER ELEVATIONS OF THE SAN
FRANCISCO PEAKS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.