Winter Storm Warning 4, NWS Grand Junction, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
400 AM MST THU DEC 1 2005

.SHORT TERM (TODAY THROUGH FRIDAY NIGHT)...DEEP MOISTURE SURGE
HAS MOVED INLAND FROM THE PACIFIC THIS MORNING AND WILL REACH THE
FORECAST AREA BY THIS AFTERNOON. ALREADY MID LEVEL DECK HAS MADE ITS
WAY OVER MOST OF THE AREA. MODELS IN AGREEMENT WITH SNOW
ACCUMULATIONS BEGINNING THIS AFTERNOON OVER THE CENTRAL AND NORTHERN
MOUNTAINS. USUALLY THIS WOULD SEEM TOO FAST IN WARM ADVECTION
PATTERN...BUT ITS HARD TO BUCK 3 MODELS. ALSO WITH STRONG WESTERLY
FLOW AND SATURATED AIR MASS BELOW MOUNTAIN TOP LEVEL...OROGRAPHICS
WILL BE A MAJOR PLAYER. EMBEDDED ENERGY AND GOOD ISENTROPIC LIFT WILL
HELP THE SITUATION. BY THIS EVENING...SNOW WILL SPREAD TO THE
SOUTHERN MOUNTAINS...AND THE HIGHER VALLEYS WILL BEGIN TO PICK UP
ACCUMULATIONS AS WELL. TEMPS TONIGHT WILL BE RELATIVELY MILD IN MOIST
WARM FLOW. THEN ON FRI...MOISTURE WILL DEEPEN AS THE STRONG WESTERLY
FLOW CONTINUES...AND A COLD FRONT WILL PUSH INTO THE NORTHWEST FRI
AFTERNOON. ONE LIMITING FACTOR FOR THE VALLEY AND PLATEAU AREAS IS
THAT TEMPS AHEAD OF THE FRONT WILL BE QUITE WARM WITH MIXED PCPN
POSSIBLE DURING THE DAY. ONCE THE FRONT MOVES IN LATE FRI
AFTERNOON/EVENING ANY REMAINING RAIN WILL SWITCH TO SNOW. LOOK FOR
COOLER TEMPS FRI NIGHT...BUT CONTINUED PCPN AND CLOUDS WILL KEEP THEM
FROM DROPPING VERY LOW.

SO IN LIGHT OF THE ABOVE...WILL UPGRADE THE WINTER STORM WATCH TO A
WARNING FOR NORTHERN AND CENTRAL CO MOUNTAINS STARTING THIS
AFTERNOON...WITH THE WESTERN SAN JUANS STARTING THIS EVENING. WILL
ALSO HOIST A SNOW ADVISORY FOR THE UPPER YAMPA RIVER BASIN STARTING
THIS EVENING. ALL HILITES WILL GO THROUGH FRI NIGHT. WEST FACING
SLOPES AND DRAINAGES WILL BE FAVORED FOR THIS EVENT WITH A TOTAL 1 TO
2 FEET POSSIBLE IN THE WARNED AREA AND UP TO A FOOT IN THE STEAMBOAT
AREA. WESTERLY WINDS AT 20 TO 30 MPH WITH STRONGER GUSTS WILL ALSO
INCREASE HAZARDOUS CONDITIONS ESPECIALLY OVER EXPOSED AND HIGHER
TERRAIN. TOYED WITH ADDING OTHER HIGH VALLEYS TO THE ADVISORY BUT
FEEL THAT TEMPS WILL BE JUST TOO WARM ON FRI EFFECTIVELY BREAKING UP
ONE EVENT INTO TWO.

.LONG TERM (SATURDAY THROUGH THURSDAY)...MODELS REMAINED IN GOOD
AGREEMENT DURING THE EARLY PORTION OF THE MEDIUM RANGE FORECAST
PERIOD. GFS/NAM/EC ALL SHOWED BROAD OPEN TROF LINGERING OVER THE
MOUNTAIN WEST BEFORE GIVING WAY TO NORTHWEST FLOW SUNDAY.

SATURDAY-SATURDAY NIGHT...EXPECT WIDESPREAD PRECIPITATION TO CONTINUE
AS DEEP PACIFIC MOISTURE CARRIED BY STRONG WESTERLY MID-LEVEL FLOW TO
CONTINUE. OROGRAPHIC LIFT WILL BE ENHANCED BY 110KT JET OVERHEAD. JET
POSITIONING COMBINED WITH LOW LEVEL MIXING RATIO HOVERING NEAR 4 G/KG
COULD LEAD TO EXTENSION OF HIGHLIGHTS...BUT A BIT TOO FAR IN THE
FUTURE TO EXTEND WARNINGS/ADVISORIES AT THIS TIME.

MOISTURE FINALLY BEGINS TO WANE LATE SATURDAY AS COLD FRONT POISED
JUST NORTH OF THE CO/WY BORDER SURGES SOUTHWARD ACROSS THE CWFA.
STILL EXPECT ENOUGH RESIDUAL MOISTURE IN PLACE TO GENERATE AREAS OF
SNOW ACROSS MUCH OF THE CWFA...THOUGH AT THIS POINT APPEARS
ACCUMULATIONS WILL BE RELATIVELY LIGHT THOUGH WOULD NOT BE SURPRISED
IF SOME AREAS RECEIVED 3 TO 6 INCHES OF NEW SNOW OVERNIGHT.
TEMPERATURES WILL BE COOL ON SATURDAY COOLING SIGNIFICANTLY DURING
THE NIGHT BEHIND THE COLD FRONT.

SUNDAY-MONDAY...NORTHWEST FLOW WILL SET IN WITH MODELS INDICATING A
SERIES OF SHORTWAVES TO DRIFT OVERHEAD. AS A RESULT...WILL HOLD ONTO
CHANCE POPS OVER MOUNTAIN LOCATIONS INTO THE EARLY PART OF THE COMING
WEEK.

TUESDAY-THURSDAY...GFS AND DGEX SNOW CARVING OUT A FAIRLY STRONG
SHORTWAVE AT MIDWEEK WHILE EC MAINTAINS A CONTINUED NORTHWEST FLOW
TUESDAY BEFORE DRIVING A SLIGHTLY WEAKER WAVE ACROSS THE CWFA ON
WEDNESDAY. GIVEN UNCERTAINTY...MADE NO CHANGES TO CHANCE MOUNTAIN
POPS TUESDAY AND WEDNESDAY. MODELS INDICATED WEAK SHORTWAVE RIDGE
FOR THURSDAY. WITH LITTLE ELSE TO GO ON...WENT AHEAD WITH DRY BUT
COOL FORECAST FOR THURSDAY.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
.CO...WINTER STORM WARNING IN EFFECT THIS AFTERNOON THROUGH FRIDAY
       NIGHT FOR ZONES 4/9/10/12/13.
      WINTER STORM WARNING IN EFFECT THIS EVENING THROUGH FRIDAY
       NIGHT FOR ZONES 18/19.
      SNOW ADVISORY IN EFFECT THIS EVENING THROUGH FRIDAY NIGHT
       FOR ZONES 5.
.UT...NONE.

&&

ELH/NL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
445 PM MST WED NOV 30 2005

COZ001>014-017>023-UTZ022>025-027>029-011300-
ANIMAS RIVER BASIN-ARCHES/GRAND FLAT-CANYONLANDS/NATURAL BRIDGES-
CENTRAL COLORADO RIVER BASIN-
CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN-
CENTRAL YAMPA RIVER BASIN-DEBEQUE TO SILT CORRIDOR-
EASTERN UINTA BASIN-EASTERN UINTA MOUNTAINS-
ELKHEAD AND PARK MOUNTAINS-FLAT TOPS-
FOUR CORNERS/UPPER DOLORES RIVER-
GORE AND ELK MOUNTAINS/CENTRAL MOUNTAINS-GRAND AND BATTLEMENT MESAS-
GRAND VALLEY-LA SAL AND ABAJO MOUNTAINS-LOWER YAMPA RIVER BASIN-
NORTHWEST SAN JUAN MOUNTAINS-PARADOX VALLEY/LOWER DOLORES RIVER-
ROAN AND TAVAPUTS PLATEAUS-SAN JUAN RIVER BASIN-SOUTHEAST UTAH-
SOUTHWEST SAN JUAN MOUNTAINS-TAVAPUTS PLATEAU-
UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-UPPER GUNNISON RIVER VALLEY-
UPPER YAMPA RIVER BASIN-WEST ELK AND SAWATCH MOUNTAINS-
445 PM MST WED NOV 30 2005

...WINTER STORM WATCH IN EFFECT FROM THURSDAY EVENING THROUGH
LATE FRIDAY NIGHT FOR THE WESTERN COLORADO MOUNTAINS...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN UTAH AND WESTERN
COLORADO.

.DAY ONE...TONIGHT.

NO SIGNIFICANT WEATHER IS EXPECTED FOR TONIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THURSDAY THROUGH SATURDAY...SNOW WILL BEGIN INCREASING THURSDAY
AFTERNOON OVER THE MOUNTAINS OF EASTERN UTAH AND WESTERN COLORADO...
AND SNOW WILL BECOME WIDESPREAD OVER THE MOUNTAINS DURING
THURSDAY NIGHT.  THE HEAVIEST SNOWFALL WILL OCCUR OVER THE HIGH
WESTERN COLORADO MOUNTAINS WHERE SIGNIFICANT SNOWFALL ACCUMULATIONS
WILL BE POSSIBLE.  ACCUMULATING SNOW WILL BE POSSIBLE AT SOME OF
THE HIGHER VALLEYS BY FRIDAY NIGHT AND SATURDAY.

SUNDAY THROUGH TUESDAY...THE ACTIVE WEATHER PATTERN WILL PERSIST
INTO THE FIRST PART OF NEXT WEEK...WHERE THE CHANCE OF ADDITIONAL
MOUNTAIN SNOWFALL CONTINUES.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED TONIGHT. HOWEVER...SPOTTERS ARE
ENCOURAGED TO REPORT NEW SNOW AND WIND INFORMATION.