FXUS65 KGJT 220449 AAA
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
945 PM MST MON DEC 21 2009

...UPDATED...

.SHORT TERM...UPDATED...TONIGHT THROUGH WEDNESDAY...
BASED ON CONSISTENCY OF EVENING MODEL RUNS WITH PREVIOUS RUNS...
DECIDED TO UPGRADE ADVISORIES TO WINTER STORM WARNINGS SW SAN
JUAN MOUNTAINS...DURANGO AREA...PAGOSA SPRINGS AREA.  ALSO ISSUING A
WINTER STORM WARNING FOR EXTREME SE UTAH ABOVE 5000 FOOT LEVEL...
MAINLY BLANDING AREA.  NO OTHER CHANGES AT THIS TIME.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
THE GFS AND ECMWF SHOW GOOD AGREEMENT IN DROPPING A SECONDARY WAVE
OVER THE FORECAST AREA WED NIGHT INTO THU ON THE HEELS OF THE ABOVE
DISCUSSED CUT OFF LOW. THE NAM HOWEVER IS MUCH WEAKER/FARTHER NORTH
WITH THIS ENERGY...JUST SHOWING SOME CHANNELIZED VORTICITY STRETCHED
NORTH-SOUTH MOVING OVER THE AREA. THE GFS AND ECMWF ARE COLDER...AND
BOTH BRING A -30 TO -32C COLD CORE AT 500 MB OVER US ON THURSDAY IN
THE NORTHWEST FLOW. THIS SITUATION FAVORS THE NORTHWEST-NORTH FACING
SLOPES...ESPECIALLY THE FLATTOPS...PARK...GORE AND ELK MOUNTAINS.
WILL GENERALLY FOLLOW THE GFS/EC SOLUTIONS FOR THIS FORECAST.
THEREFORE UPPED POPS INTO THE LIKELY CATEGORY WED NIGHT FOR THOSE
FAVORED AREAS...AND INTO THE HIGH CHANCE CATEGORY ON THU. ACTIVITY
WILL DIMINISH THU NIGHT AS MOISTURE DECREASES. AS CLOUD COVER
DIMINISHES...TEMPS WILL PLUMMET THU NIGHT. THEN... A COUPLE MORE COLD
SHOTS WILL BRUSH THE AREA IN THE NORTH/NORTHWEST FLOW INTO THE
WEEKEND...KEEPING CONDITIONS COLD AND SOMEWHAT UNSETTLED.

A FAST MOVING RIDGE PASSES OVER THE REGION ON SUN...WITH THE NEXT
SYSTEM REACHING THE AREA ON MONDAY. BOTH THE 12Z GFS AND ECMWF
INDICATE A SOUTHERN SYSTEM...BUT WITH SOME TIMING DIFFERENCES. ALSO
RUN TO RUN CONSISTENCY STILL WEAK.

HAVE CONTINUED TO UNDERCUT TEMPERATURE GUIDANCE. EXPECT THE COLD
NORTH FLOW WILL JUST REINFORCE THE VALLEY INVERSIONS. AND THERE
WILL PROBABLY BE FRESH SNOW IN MOST IF NOT ALL THE MOUNTAINS...
AND IN MANY OF THE VALLEYS.

&&

.AVIATION...UPDATED...
VFR CONDITIONS WILL CONTINUE AT ALL TAF SITES TONIGHT...EXCEPT LOCAL
MVFR DUE TO FOG/HAZE IN VEL AND GJT TAF AREAS.  LOCAL MVFR CEILINGS
AND SOME MOUNTAIN OBSCURATION WILL DEVELOP LATE TONIGHT IN AREAS
AS CLOUD BASES LOWER. A WINTER STORM WILL BRING IN MVFR AND AREAS OF
IFR CIGS AND VSBYS ACROSS THE AREA TUE...ESPECIALLY SE UT AND SW CO.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER STORM WARNING FROM TUESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON SW SAN JUAN MTS AND SOME SW CO VLYS...ZONES 19/22/23.
     WINTER WEATHER ADVISORY FROM TUESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON NW SAN JUAN MTS AND SW CORNER OF CO...ZONES 18/21.
UT...WINTER STORM WARNING FROM TUESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON EXTREME SE UT ABOVE 5000 FT LEVEL...ZONE 22.
     WINTER WEATHER ADVISORY FROM TUESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON FOR LA SAL AND ABAJO MTS...ZONE 28.

$$

SHORT TERM...MC/JRP
LONG TERM....EH
AVIATION.....JRP

$$