FXUS65 KFGZ 011807 CCA
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1055 AM MST TUE DEC 01 2009
.SYNOPSIS...EXPECT MOSTLY CLEAR SKIES AND DRY WEATHER THROUGH
SATURDAY. HIGH TEMPERATURES WILL BE A FEW DEGREES ABOVE NORMAL
THROUGH WEDNESDAY. A COLD FRONT WILL BRING SHARPLY COLDER
TEMPERATURES THURSDAY THROUGH SATURDAY MORNING. A RETURN TO WINTER
WEATHER IS POSSIBLE STARTING SUNDAY NIGHT THROUGH MUCH OF NEXT WEEK.
&&
.DISCUSSION...MOSTLY SUNNY SKIES TODAY AS YESTERDAYS SYSTEM
CONTINUES TO MOVE EAST INTO TEXAS NEAR THE BIG BEND REGION ALONG THE
RIO GRANDE. FOR NORTHERN AZ...THIS LEAVES THE AREA UNDER A SHORTWAVE
HIGH PRESSURE RIDGE WHICH IS FORECAST TO LAST THROUGH TODAY AND PART
OF WEDNESDAY. HIGH TEMPERATURES FOR TODAY WERE BUMPED UP AROUND 2
DEGREES AND ARE REFLECTED IN THE DIGITAL FORECAST. THIS CHANGE WAS
NOT SIGNIFICANT ENOUGH TO WARRANT AN UPDATE TO THE ZONE FORECAST
PACKAGE HOWEVER.
EARLY ON WEDNESDAY ANOTHER STRONG UPPER LOW AND COLD FRONT PUSHES
SOUTH INTO NORTHERN UTAH AND WYOMING AND BY LATE WEDNESDAY INTO
EARLY THURSDAY. THIS FRONT WILL BE PUSHING SOUTH AND SOUTHWEST
THROUGH THE FOUR CORNERS AREA INTO THE CHINLE VALLEY... THE
NORTHEAST PLATEAUS...AND CHUSKA MOUNTAINS. HIGHS AND LOW
TEMPERATURES WERE LOWERED ON THE MIDNIGHT SHIFT DURING
THURSDAY/FRIDAY TIME PERIOD ALONG WITH DEW POINTS IN OUR DIGITAL AND
TEXT FORECAST. LOOKING AT BREEZY NORTHEAST WINDS DURING THE SAME
TIME PERIOD.
BY LATE ON FRIDAY THE ATMOSPHERE WILL BE QUICKLY TRANSITIONING
THROUGH ANOTHER HIGH PRESSURE RIDGE AS YET ANOTHER LOW PRESSURE
TROUGH BEGINS TO CARVE OUT A PATH INTO THE WASHINGTON/OREGON/IDAHO
AREA WHICH WILL MARK THE BEGINNING OF A MUCH DEEPER LOW CARVING OUT
OVER THE WESTERN NORTH AMERICA REGION AS THE WEEKEND BEGINS.
ANOTHER NOTE WORTHY REGION TO BE PLACING OUR EYES ON IS THE AREA IN
THE EASTERN PACIFIC JUST WEST OF BAJA. IN THIS REGION THERE IS
FORECAST TO BE SIGNIFICANT AMOUNTS OF SUBTROPICAL MOISTURE POOLED IN
THIS AREA. CURRENTLY THIS MOISTURE IS INDICATED TO BE AROUND 130
WEST AND IS FORECAST TO MOVE EAST TO AROUND 120 W BY SATURDAY.
FROM SATURDAY ON...THIS IS WHERE THE ATMOS MODELS BEGIN TO DIVERGE
AND RUN-TO-RUN CONSISTENCY BEGINS TO GO DOWN MAKING THE
PREDICTABILITY GO DOWN AND FORECAST UNCERTAINTY ON THE INCREASE. AT
THIS POINT WE CAN LIST SOME OF THE PARAMETERS OF THE FORECAST WE
HAVE A HIGHER DEGREE OF CONFIDENCE. CERTAINLY WE CAN SAY WINDY
CONDITIONS AND COOLER TEMPERATURES FOR SUNDAY INTO WEDNESDAY WITH
INCREASES IN MOISTURE FOR THE REGION.
THE TROUGH PATTERN...IN OTHER WORDS HOW THIS SYSTEM WILL MOVE ACROSS
THE SOUTHWEST STATES WILL AFFECT WHAT KIND OF WEATHER NORTHERN
ARIZONA WILL RECEIVE DURING THE SUNDAY...MONDAY...TUESDAY...AND
EARLY WEDNESDAY TIME PERIOD. CURRENTLY ON THE TABLE IS A SYSTEM THAT
COULD BRING IN A MORE MOIST SUBTROPICAL AIRMASS WITH HIGHER SNOW
LEVELS AT OR ABOVE 6500 TO 7500 FEET...AND THAT IS CLOSEST TO THE
ECMWF MODEL. ECMWF MODEL HAS A STRONG RIDGE OFF OF WESTERN NO.
AMERICA EXTENDING UP INTO ALASKA WITH LOW PRESSURE UNDER CUTTING THE
RIDGE AND PICKING UP THE RELATIVELY WARM SUBTROPICAL MOIST POOL WEST
OF BAJA. HOWEVER THE ECMWF PUTS ARIZONA INTO A MOIST ZONAL FLOW WITH
MINOR DISTURBANCES MOVING THROUGH BASICALLY FROM MONDAY OF NEXT WEEK
INTO THURSDAY. THE OTHER POSSIBLE VARIATION TO A SYSTEM IN THE
SOUTHWEST U.S. (AS FORECAST BY THE GFS) WOULD BE A OMEGA BLOCK TYPE
OF PATTERN( AGAIN WITH THE RIDGE OF HIGH PRESSURE OFF OF WESTERN NO.
AMERICA EXTENDING UP INTO ALASKA) WITH A COLD AND SLOW MOVING CLOSED
LOW SYSTEM DROPPING SOUTH THROUGH THE GREAT BASIN THEN INTO SOUTHERN
NEVADA AND THEN ACROSS NORTHERN AZ LATER ON TUESDAY AND THEN MOVING
EAST ON WEDNESDAY. THIS PATTERN IS MUCH COLDER WITH LOWER SNOW
LEVELS...MUCH STRONGER LARGE SCALE LIFT CONCENTRATED OVER A TUESDAY
INTO EARLY WEDNESDAY TIME FRAME...AND SIMILAR AMOUNTS OF QPF (OR
MODEL PREDICTED PRECIPITATION) AS THE ECMWF. THESE ARE THE TWO BASIC
MODEL SCENARIOS THAT COULD HAPPEN.
FOR NOW THE DIGITAL FORECAST WILL HAVE BREEZY TO WINDY CONDITIONS
SUNDAY INTO MONDAY. COLDER HIGH TEMPS MONDAY INTO TUESDAY...
CURRENTLY IN THE FORECAST. MORE MOIST CONDITIONS STARING LATE SUNDAY
INTO TUESDAY AND INCREASING MOISTURE MONDAY INTO TUESDAY...CURRENTLY
IN THE FORECAST. POPS WERE RAISE ON THE MIDNIGHT SHIFT...ONLY MINOR
TWEAKS WILL BE NEED AT THIS POINT.
&&
.AVIATION...FOR THE 18Z PACKAGE...EXPECT VFR CONDITIONS UNDER CLEAR
SKIES...AND LIGHT WINDS.
KGCN METAR OBS ARE UNAVAILABLE...SVC TECH ON SITE. KGCN TAF IS
AMD NOT SKED UNTIL FURTHER NOTICE.
AVIATION DISCUSSION NOT UPDATED FOR AMENDMENTS.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC..................TC
AVIATION/FIRE WEATHER...MAS
VISIT WEATHER.GOV/FLAGSTAFF FOR NORTHERN ARIZONA WEATHER INFORMATION.
