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000
FXUS65 KGJT 081103
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
403 AM MST SUN DEC 8 2013

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 403 AM MST SUN DEC 8 2013

AT 330 AM MST...RADAR RETURNS AND SURFACE OBSERVATIONS INDICATE
THAT THE HEAVIEST SNOW HAS BEGUN TO WIND DOWN OVER THE WESTERN
HALF OF THE AREA. THIS HEAVIER SNOW HAS BEEN ASSOCIATED WITH THE
COLD FRONT AND THE 700MB TROUGH. AND BOTH SHOULD BE EAST OF THE
DIVIDE AS THIS FORECAST GOES TO PRESS. RADAR IMAGES ALSO SHOW A
MORE CELLULAR NATURE TO THE ECHOS MOVING OVER EASTERN UTAH AND
INTO WESTERN CO AS THE SNOW BECOMES MORE SHOWERY. THEREFORE FEEL
THAT THE MOST ENERGETIC PORTION OF THE STORM HAS ALREADY OCCURRED.
THE 500MB TROUGH AND COLD POOL ALOFT ARE STILL JUST UPSTREAM AND
WILL REACH THE CO/UT AROUND 6AM MST...AND ACROSS THE DIVIDE BY
AROUND MIDDAY. THEREFORE SNOW WILL CONTINUE TO BE WIDESPREAD
THROUGH THE MORNING...DIMINISHING FROM THE WEST. THE WESTERN
VALLEYS WILL PROBABLY SEE LITTLE ADDITIONAL ACCUMULATIONS...BUT I
WILL NOT DROP ANY ADVISORIES AT THIS TIME AS LIGHT SNOW SHOULD
LINGER THERE THROUGH THE MORNING. ALSO WILL GO AHEAD AND LET THE
LIGHT OF DAY GIVE US A BETTER PICTURE OF ANY ONGOING ACTIVITY.
SNOW WILL CONTINUE TO ACCUMULATE OVER ALL MOUNTAIN AREAS
TODAY...DIMINISHING FROM THE SOUTH AND WEST THIS AFTERNOON. THE
NORTHERN MOUNTAINS WILL BECOME MORE FAVORED IN THE WEST-NORTHWEST
FLOW...HOWEVER MOISTURE WILL BEGIN TO DIMINISH AS DRIER AIR MOVES
IN ALOFT. BUT SINCE THE NORTH DID NOT REALLY FEEL THE EFFECTS OF
THE COLD FRONT BECAUSE IT STAYED SOUTH OF THE TAVAPUTS...THAT AREA
WILL PROBABLY SEE MUCH BETTER SNOWFALL TODAY AND TONIGHT THAN WHAT
HAS FALLEN THERE IN THE LAST 18-24 HOURS.

THE NORTHWEST FLOW BEHIND THE TROUGH QUICKLY BECOMES WESTERLY LATE
THIS AFTERNOON/EVENING AS ANOTHER REINFORCING COLD WAVE MOVES OVER
WY-NORTHWEST UT BY MIDNIGHT...AND THEN INTO NORTHEAST UT/NORTHWEST
CO BY DAYBREAK. AS THIS WAVE PASSES ON MONDAY...A NORTHWEST FLOW
WILL FINALLY DEVELOP IN ITS WAKE. THIS WILL RESULT IN CONTINUED
OROGRAPHIC SNOW OVER THE NORTHERN DIVIDE MOUNTAINS DURING THE
MORNING...WITH SOME SNOW LINGERING INTO THE AFTERNOON.

WHEN COMPARED TO THE VERY COLD TEMPERATURES LAST WEEK...HIGHS
TODAY MAY SEEM ON THE MILD SIDE TODAY IN SPITE OF STAYING WELL
BELOW NORMAL. THEN LOWS TONIGHT WILL PLUMMET...ESPECIALLY WHERE
SOME CLEARING TAKES PLACE. VERY COLD CONDITIONS WILL TAKE HOLD
AGAIN ON MONDAY IN THE COLD AND STABLE NORTHWEST FLOW.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 403 AM MST SUN DEC 8 2013

MODELS WERE SIMILAR THROUGH THURSDAY...SO CONFIDENCE IS BETTER
THAN AVERAGE THROUGH THE BETTER PART OF THE WEEK AHEAD.

EXPECTING DRY...BUT COLD CONDITIONS MONDAY NIGHT IN THE WAKE OF
THIS WEEKEND/S STORM AS CLEARING SKIES AND FRESH SNOW COVER BRING
ABOUT GOOD RADIATIONAL COOLING. ON TUESDAY AND TUESDAY NIGHT A
WEAK SHORTWAVE IN THE NORTHWESTERLY FLOW COULD BRING ABOUT SOME
LIGHT SNOW OVER THE ELKHEAD AND GORE RANGES...AND A PORTION OF
THE FLATTOPS AS WELL. ACCUMULATIONS APPEAR LIGHT SO DO NOT
ANTICIPATE HILITES.

DRY AND LESS COLD CONDITIONS FROM MID-SLOPE UPWARD EXPECTED
WEDNESDAY AND THURSDAY AS A RIDGE OF HIGH PRESSURE BUILDS OVER
THE AREA. LOWER VALLEYS WILL BE STUCK BENEATH THE INVERSION SO
LITTLE RELIEF FROM THE COLD EXPECTED. MODEL DIFFERENCES APPEAR
TOWARD THE END OF THE WEEK AS MORE PROGRESSIVE GFS BRINGS A
PACIFIC TROUGH ACROSS THE FORECAST AREA FRIDAY AND FRIDAY NIGHT
FOR A CHANCE OF SNOW SHOWERS. IN CONTRAST...THE ECMWF SOLUTION
FEATURED A WEAK REX BLOCK OVER THE AREA AND HELD THE TROUGH OFF
TO THE WEST. ON SATURDAY...NO PRECIPITATION INDICATED IN EITHER
MODEL THOUGH GFS DEVELOPED A RIDGE OVER THE AREA WHILE A WEAK
TROUGH AND DEFORMATION WAS OFFERED UP BY THE EC. GIVEN
DIFFERENCES...WILL CONTINUE WITH THE BLENDED SOLUTION FRIDAY AND
SATURDAY.

AS MENTIONED PREVIOUSLY...EXPECT VALLEYS WILL REMAIN INVERTED...
THUS COLDER THAN NORMAL DURING THE PERIOD. QUESTION IS HOW MUCH
MODERATION CAN BE EXPECTED. BIAS CORRECTED GRIDS SUGGEST READINGS
WILL REMAIN BELOW FREEZING WHICH SEEMED REASONABLE. MEANWHILE...
SLOPES AND HIGHER ELEVATIONS SHOULD SEE LESS COLD CONDITIONS AS A
RIDGE BUILDS AT MIDWEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 403 AM MST SUN DEC 8 2013

A WINTER STORM WAS PUSHING EASTWARD ACROSS THE FORECAST AREA EARLY
THIS MORNING. EXPECT THIS SYSTEM WILL CONTINUE TO BRING WIDESPREAD
SNOWFALL TO MUCH OF WESTERN COLORADO THIS MORNING. AS A RESULT...
MOUNTAINS TO BE OBSCURED WITH MANY AIRPORTS EXPERIENCING MVFR CIGS
AND VSBY WITH A FEW HAVING OCCASIONAL IFR CONDITIONS. MEANWHILE...
EXPECT VFR CONDITIONS ACROSS EASTERN UTAH.

SNOW WILL BE DECREASING DURING THE DAY...BECOMING CONFINED TO THE
NORTHERN AND CENTRAL MOUNTAINS BY LATE AFTERNOON.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER WEATHER ADVISORY UNTIL 2 PM MST THIS AFTERNOON FOR COZ001.

     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR COZ006-011-020.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR COZ007-
     008-014.

     WINTER STORM WARNING UNTIL 6 AM MST MONDAY FOR COZ009-012.

     WINTER STORM WARNING UNTIL 6 PM MST THIS EVENING FOR COZ017>019.

     WINTER WEATHER ADVISORY UNTIL 6 AM MST MONDAY FOR COZ002>004-010-
     013.

     WINTER STORM WARNING UNTIL NOON MST TODAY FOR COZ021>023.

UT...WINTER WEATHER ADVISORY UNTIL 2 PM MST THIS AFTERNOON FOR
     UTZ023>025-028.

     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR UTZ027.

     WINTER WEATHER ADVISORY UNTIL 9 AM MST THIS MORNING FOR UTZ022-
     029.

&&

$$

SHORT TERM...EH
LONG TERM...NL
AVIATION...NL