Severe Thunderstorm Warning 90, NWS Flagstaff, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
320 PM MST FRI SEP 09 2005

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM MOVING INTO NORTHERN
ARIZONA TODAY IS ALSO BRINGING DRY AIR ALOFT INTO THE STATE.
HOWEVER...A SLIGHT CHANCE OF THUNDERSTORMS WILL CONTINUE INTO THE
EARLY EVENING FROM FLAGSTAFF EASTWARD WITH A CHANCE FOR STRONG
STORMS...SOME WITH HAIL AND STRONG GUSTY WINDS...IN GILA...NAVAJO
AND APACHE COUNTIES. BY MIDNIGHT...MOST STORMS SHOULD END EXCEPT
POSSIBLY IN THE FOUR CORNERS AREA. A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS WILL REMAIN NEAR THE NEW MEXICO BORDER THROUGH SUNDAY.
COOLER...BREEZY...AND DRY WEATHER IS EXPECTED FOR MOST OF NEXT WEEK.

&&

.DISCUSSION...THE SHORTWAVE TROUGH MOVING INTO AZ AT THIS TIME IS
BRINGING A VERY DRY AIRMASS ALOFT RAPIDLY THROUGH THE
STATE...LIMITING CONVECTION UNDERNEATH DUE TO DRY AIR ENTRAINMENT.
18Z KFGZ SOUNDING SHOWS THIS DRY LAYER FROM AROUND 550 MB AND UPWARD
WHILE A 20Z SOUNDING TAKEN FROM PRESCOTT SHOWS THIS DRY AIR HAS
DESCENDED BELOW 650 MB. 18Z GFS RUN HAS A GOOD HANDLE ON THE
SITUATION AND SHOWS THAT THE POTENTIAL FOR SEVERE WEATHER WILL
RAPIDLY BE MOVING EASTWARD ALTHOUGH THE VORTICITY CENTER MOVING INTO
THE STATE MAY CATCH UP WITH THE MOISTURE IN THE FOUR CORNERS AREA
AROUND MIDNIGHT...SO STRONG THUNDERSTORMS MAY LINGER THERE WELL INTO
THE NIGHT.

OVER THE WEEKEND...A COLD 500 MB TROUGH WILL DEEPEN OVER THE GREAT
BASIN KEEPING DRY WESTERLY FLOW PUSHING INTO AZ. ENOUGH MOISTURE MAY
LINGER NEAR THE NM BORDER FOR A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS THROUGH SUNDAY AFTERNOON. AS THE WEEK GOES ON...HIGH
PRESSURE OVER THE PLAINS WILL PUSH EASTWARD ALLOWING DRY WESTERLIES
TO PENETRATE FARTHER ACROSS THE SOUTHWEST...BRINGING CLEARER SKIES
AND DRY CONDITIONS ACROSS THE STATE. ALONG WITH THE CLEAR SKIES AND
DRY ATMOSPHERE...COOL NIGHTTIME TEMPERATURES WILL AFFECT NORTHERN
ARIZONA WITH MINIMUM TEMPERAURES INTO THE 30S IN THE HIGH COUNTRY
FOR MOST OF NEXT WEEK. ALSO...EXPECT BREEZY AFTERNOON WINDS EACH DAY
THROUGH NEXT WEEK DUE TO TIGHT HEIGHT GRADIENTS ASSOCIATED WITH THE
TROUGHING ACROSS THE WESTERN US.

&&

.AVIATION...FOR 00Z PACKAGE...WIDELY SCATTERED TS COVERAGE IS
EXPECTED TO CONTINUE THROUGH MIDNIGHT WITH MOST ACTIVITY ACROSS THE
EASTERN PORTIONS OF THE STATE. CURRENTLY ELEVATED WIND SPEEDS WILL
DECREASE AFTER SUNSET WITH MOST TAF SITES EXPERIENCING SOUTHWEST
SUSTAINED WINDS REDUCED TO BELOW 15KTS AFTER 05Z. GUSTY...BUT
DRY...CONDITIONS WILL REDEVELOP TOMORROW MORNING AFTER 16Z-18Z.
AVIATION DISCUSSION NOT UPDATED FOR AMENDMENTS.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

DJO/KD

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
130 PM MST FRI SEP 9 2005

AZZ004>018-037>040-100700-
WESTERN MOGOLLON RIM-GRAND CANYON COUNTRY-YAVAPAI COUNTY MOUNTAINS-
YAVAPAI COUNTY VALLEYS AND BASINS-OAK CREEK AND SYCAMORE CANYONS-
MARBLE AND GLEN CANYONS-KAIBAB PLATEAU-COCONINO PLATEAU-
NORTHEAST PLATEAU AND MESAS HWY 264 NORTHWARD-
NORTHEAST PLATEAU AND MESAS SOUTH OF HWY 264-
CHINLE VALLEY-CHUSKA MOUNTAINS AND DEFIANCE PLATEAU-
BLACK MESA AREA-LITTLE COLORADO RIVER VALLEY IN COCONINO COUNTY-
LITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTY-
LITTLE COLORADO RIVER VALLEY IN APACHE COUNTY-
EASTERN MOGOLLON RIM-WHITE MOUNTAINS-NORTHERN GILA COUNTY-
130 PM MST FRI SEP 9 2005

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

.DAY ONE...TODAY

DRY AIR ALOFT MOVING INTO THE AREA AHEAD OF A STRONG LOW PRESSURE
SYSTEM HAS ALREADY LIMITED THUNDERSTORM DEVELOPMENT IN MOST OF
COCONINO AND YAVAPAI COUNTIES SOUTH OF THE GRAND CANYON...WITH
MINIMAL THREAT OF SEVERE WEATHER EXPECTED FOR THE REST OF TODAY. DRY
AIR ALOFT WILL CONTINUE TO MOVE EASTWARD...EVENTUALLY SHUTTING OFF
THUNDERSTORM ACTIVITY OVER ALL OF COCONINO AND YAVAPAI COUNTY BY
SUNSET. EXPECT THUNDERSTORM ACTIVITY TO CONTINUE PAST MIDNIGHT IN
THE FOUR CORNERS REGION OF NORTHERN APACHE COUNTY. THE MAIN SEVERE
WEATHER THREAT TODAY IS LARGE HAIL EXCEEDING 1 INCH DIAMETER IN
ISOLATED STORMS. STRONG WIND GUSTS EXCEEDING 60 MPH ARE ALSO
POSSIBLE IN SOME OF THE STRONGEST STORMS. DUE TO THE NATURE OF THE
WINDS ALOFT TODAY...EVEN AN ISOLATED TORNADO IS ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

SHOWER ACTIVITY IS EXPECTED TO RAPIDLY DECREASE FROM WEST TO EAST
EARLY SATURDAY MORNING WITH ONLY ISOLATED THUNDERSTORMS POSSIBLE
NEAR THE NEW MEXICO BORDER BY SATURDAY AFTERNOON. MAINLY DRY WEATHER
IS EXPECTED FOR THE REMAINDER OF THE EXTENDED FORECAST PERIOD.

.SPOTTER INFORMATION STATEMENT...

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