Severe Thunderstorm Warning 51, NWS Flagstaff, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
930 AM MST TUE SEP 13 2011

.SYNOPSIS...A LOW PRESSURE SYSTEM OVER THE SOUTHWESTERN STATES WILL
BRING A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH WEDNESDAY.
COOLER THAN NORMAL TEMPERATURES WILL CONTINUE. EXPECT A SIGNIFICANT
DRYING TREND BY THE END OF THE WEEK WITH HIGH TEMPERATURES WARMING
BACK TO AROUND SEASONAL AVERAGES.

&&

.DISCUSSION...ANOTHER ACTIVE DAY ANTICIPATED FOR NORTHERN AZ. UPPER
LOW OVER SOUTHERN CA WILL CONTINUE TO PROVIDE A FAVORABLE DIFFLUENT
FLOW ACROSS THE STATE THROUGH WEDNESDAY. VERTICAL WIND SHEAR LOOKS
LESS IMPRESSIVE TODAY BUT SUFFICIENT MOISTURE AND INSTABILITY WILL
STILL ALLOW SCATTERED TO NUMEROUS SHOWERS AND STORMS TO DEVELOP.
THIS EVENING AND TONIGHT LOOK TO REMAIN ACTIVE AS THE CA LOW PUSHES
INTO WESTERN AZ. DYNAMIC LIFT AND A BIT MORE SHEAR WILL HELP TO
SUSTAIN CONVECTION OVERNIGHT. WILL BE LOOKING AT THIS FURTHER AND
ADJUSTING TONIGHTS FORECAST WITH THE AFTERNOON PACKAGE. FOR
NOW...HAVE MADE MINOR TWEAKS TO TODAYS FORECAST. BELIEVE THE SEVERE
THREAT WILL BE A BIT MORE ISOLATED TODAY...BUT SOME STORMS MAY
PRODUCE LARGE HAIL...DAMAGING WINDS...AND LOCALIZED FLOODING.

&&

.PREVIOUS DISCUSSION (230 AM)...MORE UPPER LEVEL DISTURBANCES
ROTATING AROUND THE UPPER LOW OFF THE SOUTHERN CALIFORNIA COAST WILL
HELP ENHANCE CONVECTION ACROSS THE AREA AGAIN TODAY.

TODAY THE UPPER LOW OFF THE SOUTHERN CALIFORNIA COAST BEGINS TO
TRANSLATE INLAND ACROSS SOUTHERN CAL...FOR ARIZONA COOLER
TEMPERATURES ALOFT...DIFFLUENCE...UPPER JET...AND MOISTURE ALL GO
INTO SUPPORTING SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS THE
REGION...ALONG WITH THE THREAT OF ISOLATED HEAVY RAIN THAT COULD
POSSIBLY LEAD TO ISOLATE FLASH FLOODING...ISOLATED SEVERE HAIL AND
STRONG WIND GUSTS.

BY WEDNESDAY THE UPPER LOW FINALLY MOVES ACROSS NORTHWEST SECTIONS
OF THE STATE. BY THEN THE ATMOS DRIES SOMEWHAT ACCORDING TO MODEL
GUIDANCE...HOWEVER WITH THE COLDER TEMPERATURES ALOFT AND GREATER
INSTABILITY THE ATMOS WILL STILL LIKELY DELIVER A SCATTERED
PROBABILITY OF STORMS.

BY THURSDAY...THE LOW LIFTS NORTHEAST INTO SOUTHERN UTAH...STILL
ENOUGH INSTABILITY FOR ISOLATED STORMS OVER WESTERN COCONINO TO
SCATTERED STORMS OVER PORTIONS OF NAVAJO AND APACHE COUNTIES.

FRIDAY AND SATURDAY...INCREASING HEIGHTS AND DRIER AIR WILL REDUCE
STORM CHANCES TO NEAR ZERO TO ISOLATED AT BEST OVER THE NORTHEAST
AND ALONG THE UTAH BORDER.

SUNDAY THROUGH TUESDAY...DRIER AIR AND INCREASE HEIGHTS WILL HELP
KEEP THE REGION DRY WITH HIGH TEMPERATURES RETURNING TO AROUND
SEASONAL VALUES.

&&

.AVIATION...FOR THE 18Z PACKAGE...SCT/NMRS TSRA WILL REDEVELOP TODAY
WITH STRONG GUSTY WINDS UP TO 50KTS... HAIL UP TO ONE INCH...AND
MVFR/IFR CONDITIONS PSBL IN THE STRONGER STORMS. AREAS OF RAIN WITH
EMBEDDED THUNDERSTORMS ARE EXPECTED THROUGH THE NIGHT AS WELL.
AVIATION DISCUSSION NOT UPDATED FOR AMENDMENTS.

&&

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

&&

PUBLIC..................MCS
AVIATION................MAS

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF.

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
412 AM MST TUE SEP 13 2011

AZZ004>018-037>040-141100-
KAIBAB PLATEAU-MARBLE AND GLEN CANYONS-GRAND CANYON COUNTRY-
COCONINO PLATEAU-YAVAPAI COUNTY MOUNTAINS-
NORTHEAST PLATEAUS AND MESAS HWY 264 NORTHWARD-CHINLE VALLEY-
CHUSKA MOUNTAINS AND DEFIANCE PLATEAU-
LITTLE COLORADO RIVER VALLEY IN COCONINO COUNTY-
LITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTY-
LITTLE COLORADO RIVER VALLEY IN APACHE COUNTY-
WESTERN MOGOLLON RIM-EASTERN MOGOLLON RIM-WHITE MOUNTAINS-
NORTHERN GILA COUNTY-YAVAPAI COUNTY VALLEYS AND BASINS-
OAK CREEK AND SYCAMORE CANYONS-BLACK MESA AREA-
NORTHEAST PLATEAUS AND MESAS SOUTH OF HWY 264-
412 AM MST TUE SEP 13 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
ARIZONA...NORTH CENTRAL ARIZONA...NORTHEAST ARIZONA AND WEST
CENTRAL ARIZONA.

.DAY ONE...TODAY AND TONIGHT

TODAY THE UPPER LOW OFF THE SOUTHERN CALIFORNIA COAST BEGINS TO
TRANSLATE INLAND ACROSS SOUTHERN CAL...FOR NORTHERN ARIZONA
EXPECT SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS THE
REGION...ALONG WITH THE THREAT OF ISOLATED HEAVY RAIN THAT COULD
POSSIBLY LEAD TO ISOLATE FLASH FLOODING...ISOLATED SEVERE HAIL AND
STRONG WIND GUSTS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE ATMOSPHERE WILL REMAIN MOIST AND UNSTABLE FOR WEDNESDAY AS THE
UPPER LOW MOVES ACROSS NORTHWEST ARIZONA. SCATTERED THUNDERSTORMS
ARE POSSIBLE AGAIN ON WEDNESDAY WITH THE STRONGER STORMS OVER
PORTIONS OF COCONINO COUNTY...NORTHERN GILA...NAVAJO AND APACHE
COUNTIES. THURSDAY INTO FRIDAY THERE WILL BE A DOWNWARD TREND IN
THUNDERSTORM ACTIVITY AS DRIER AND MORE STABLE AIR COMES IN FROM
THE WEST BEHIND THE DEPARTING LOW PRESSURE SYSTEM.

SPOTTER INFORMATION STATEMENT...

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

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
116 PM MST TUE SEP 13 2011

AZZ013-016-132100-
NAVAJO AZ-
116 PM MST TUE SEP 13 2011

THE NATIONAL WEATHER SERVICE IN FLAGSTAFF HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  SOUTH CENTRAL NAVAJO COUNTY IN NORTHEAST ARIZONA

UNTIL 200 PM MST

AT 111 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 9 MILES NORTHWEST OF ARIPINE...OR 5 MILES NORTH
OF HEBER...MOVING EAST AT 15 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.

LOCATIONS IMPACTED INCLUDE...
   ARIPINE...STATE ROUTE 377 FROM MILEPOSTS 0 TO 10.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF YOU ARE IN THE ADVISORY AREA AND STORMS APPROACH...TAKE SHELTER IN
A STURDY BUILDING.

&&

LAT...LON 3468 11024 3445 11016 3438 11061 3455 11067
TIME...MOT...LOC 2014Z 254DEG 13KT 3449 11054

JJ