FXUS65 KGJT 091146
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
445 AM MST WED DEC 9 2009

.SHORT TERM...VERY COLD TEMPERATURES ABOUND THIS MORNING...EXCEPT
WHERE STRATUS CLOUDS ARE PROVIDING SOME SHELTER. THE LAST TIME GRAND
JUNCTION HIT -10F WAS 22DEC98.

THE WESTERN EDGE OF A 150KT JET STREAK WAS OVER THE CENTRAL FORECAST
AREA THIS MORNING AND EXITING EAST. THIS WILL BREAK DOWN THE
DEFORMATION ZONE OVER THE NW COLORADO. BUT A WEAK DISTURBANCE DIVES
IN FROM THE NW THIS AFTERNOON. THIS SHOT OF COLD ADVECTION STEEPENS
THE LAPSE RATES OVER THE PARK/GORE/FLATTOPS. FORECAST SOUNDINGS
INDICATE A NEAR SATURATED UNSTABLE LAYER UP TO 12KFT MSL. SO SNOWFALL
OVER THE NORTHERN MTNS WILL SHOW A DOWNTURN THIS MORNING BEFORE
PICKING UP AGAIN THIS AFTERNOON. THEREFORE LEFT THE ADVISORIES IN
PLACE. EVEN WITHOUT SNOWFALL THE MOUNTAINS WILL BE BITTER COLD TODAY
WITH TEMPERATURES STRUGGLING TO CLIMB ABOVE ZERO F AND W-NW GRADIENT
WINDS GUSTING TO 35 MPH OVER EXPOSED TERRAIN. STRATUS CLOUDS ALONG W-
NW-FACING SLOPES WILL PRODUCE AREAS OF FREEZING FOG.

VALLEYS WON'T BE A LOT WARMER BUT WILL BE GENERALLY DECOUPLED FROM
THE GRADIENT WINDS ALOFT.

SNOWFALL WILL END TONIGHT WITH LOSS OF FORCING AND A SLACKENING MTN
TOP GRADIENT.  CLEARING SKIES FOR ALL LOCATIONS WILL ALLOW
TEMPERATURES TO PLUMMET AGAIN. ICE FOG FORMATION IS POSSIBLE
NOW FAVORING THE VALLEYS AS THE COLD SURFACE LAYER BEGINS TO SATURATE
FROM THE SNOWPACK.

THURSDAY-THURSDAY NIGHT: WARM ADVECTION ALOFT BEGINS AS THE FLOW
BACKS TO W THEN SW. FOG COULD PERSIST IN FAVORED LOCATIONS SUCH AS
THE UINTA AND GUNNISON BASINS AND ALONG THE COLORADO RIVER.

.LONG TERM...FRIDAY THROUGH TUESDAY...

ACTIVE WEATHER PATTERN REMAINS IN PLACE WITH ANOTHER IMPRESSIVE SURGE
OF PACIFIC MOISTURE POISED TO MOVE INTO THE REGION. THE ECMWF AND GFS
IN GOOD AGREEMENT WITH BRINGING A SERIES OF QUICK MOVING WAVES INTO
THE FORECAST AREA...BEGINNING FRIDAY AFTERNOON AND CONTINUING THROUGH
THE WEEKEND. THE STRONGEST SYSTEM SEEMS TO CENTER AROUND THE SATURDAY
NIGHT AND SUNDAY TIMEFRAME AND HAVE STARTED TO FOCUS ON ADJUSTING
POPS UPWARD DURING THIS PERIOD. ONCE AGAIN...SIGNIFICANT SNOWFALL
APPEARS LIKELY FOR PORTIONS OF THE FORECAST AREA...ALTHOUGH THE FINE
DETAILS STILL NEED TO BE WORKED OUT. BASED ON THE PROJECTED PATH OF
THE UPPER LEVEL JET AND OPENED NATURE OF THIS WAVE...FEEL THE
HEAVIEST SNOWFALL WILL BE KEYING ON THE CENTRAL AND SOUTHWEST
MOUNTAINS WITH EMPHASIS SHIFTING TO THE NORTHERN MOUNTAINS LATE
SUNDAY AND MONDAY AS FLOW ALOFT BECOMES MORE NORTHWESTERLY BEHIND THE
TROUGH. HIGHLIGHTS MAY AGAIN BE NECESSARY AND WILL BE ISSUED AS WE
GET CLOSER TO THE MAIN EVENT.  FLAT RIDGING THEN ARRIVES TUESDAY
WITH DRIER CONDITIONS EXPECTED.

&&

.AVIATION...

AREAS OF MVFR AND LOCAL IFR CONDITIONS ARE POSSIBLE ALONG THE W-NW
SLOPES OF THE CO MTNS. OTHERWISE VFR CONDITIONS ARE EXPECTED OVER
MOST VALLEY AREAS TODAY AND TONIGHT. SNOW AND BLOWING SNOW WILL
CONTINUE OVER THE HIGHER MOUNTAINS THIS THROUGH THIS EVENING...
ESPECIALLY NEAR THE CONTINENTAL DIVIDE. VALLEY FOG FORMATION AND
RESULTING IFR CONDITIONS ARE POSSIBLE WEDNESDAY NIGHT ESPECIALLY AT
KASE...KEGE...KVEL.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER WEATHER ADVISORY FOR SNOW/BLOWING SNOW THROUGH 6 AM
          THURSDAY MORNING FOR THE NWRN CO MOUNTAINS (ZONES 4/10/13).
     WINTER WEATHER ADVISORY FOR BLOWING SNOW THROUGH 6 PM TODAY
          (ZONES 12/18/19).
UT...NONE.

&&

$$

SHORT TERM...JOE
LONG TERM....JDC
AVIATION.....JOE+ELH