Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 251050
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
350 AM MST THU DEC 25 2014

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 346 AM MST THU DEC 25 2014

THE CHRISTMAS STORM OF 2014 WAS GENERALLY BEGINNING AS ADVERTISED
THIS EARLY MORNING WITH WARM-SECTOR SNOW SPREADING INTO THE
NORTHERN ZONES AFTER MIDNIGHT. AT 3 AM SNOTEL SITES HAD NOT
REGISTERED ACCUMULATIONS BUT STEAMBOAT SPRINGS ROADS WERE
SNOWPACKED.

THE UPPER TROUGH WILL DIG THROUGH THE GREAT BASIN TODAY CLOSING
OVER UTAH BY THIS AFTERNOON. IT SLOWLY PROGRESSES TO THE FOUR
CORNERS TONIGHT THEN BEGINS TO OPEN AND LIFT THROUGH COLORADO ON
FRIDAY. THIS STORM HAS DECENT COLD AIR...-30C AT 500MB...BUT
MARGINAL MOISTURE...0.39 PW. ITS 85KT JET NOSE LINGERS OVER
SOUTHERN COLORADO THROUGH THE DAY PROVIDING UPPER DIVERGENCE. THE
BEST LOW LEVEL CONVERGENCE OCCURS THIS MORNING ACROSS THE NORTH
WITH THE COLD FRONT. THEN A WEAK CONVERGENT CENTER LINGERS OVER
THE CENTRAL COLORADO MOUNTAINS THROUGH FRIDAY. LAPSE RATES OVER
THE CENTRAL CO MTNS INCREASE TO 7.5 C/KM THIS AFTERNOON AND AGAIN
ON FRIDAY AFTERNOON ADDING A CONVECTIVE COMPONENT TO THIS STORM.
THIS WILL PRODUCE SOME LARGE LOCAL VARIATION IN SNOW AMOUNTS.
WITH THIS IN MIND HAVE ISSUED ADVISORIES FOR THE GUNNISON BASIN
AND THE PAGOSA SPRINGS ZONE THROUGH FRIDAY EVENING.

A RAIN SNOW MIX MAY OCCUR THIS AFTERNOON BELOW 5000FT BUT
OTHERWISE THIS STORM WILL BE ALL SNOW. BY FRIDAY EVENING MOST
MOUNTAIN RANGES WILL SEE 6-12 INCHES. THE EASTERN VALLEYS WILL
HAVE 2-4 INCHES WITH ALL BUT SE UTAH VALLEYS RECEIVING SOME LIGHT
ACCUMULATIONS.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 346 AM MST THU DEC 25 2014

AT THE BEGINNING OF THE EXTENDED PERIOD THE MODELS MOVE THE MAIN
UPPER TROUGH EAST OF THE AREA. DRIER NW FLOW ALOFT SPREADS OVER
THE AREA...BRINGING A BRIEF RESPITE FROM THE UNSETTLED WINTER
WEATHER. SATURDAY SHOULD BE THE DRIEST DAY IN THE FORECAST BECAUSE
THE NEXT WEATHER SYSTEM WILL START INFLUENCING WEATHER OVER NE UT
AND NW CO SAT EVENING. A STRONG JET PARALLELING THE OR AND WA
COAST WILL CAUSE THIS NEXT SYSTEM TO DIG INTO PACNW AND THE GREAT
BASIN SUN NIGHT. BY SUNRISE MONDAY THE POLAR FRONT WILL EXTEND
FROM NORTHERN CA THROUGH SOUTHERN NV...UT AND CO. THE ARCTIC FRONT
WITH A MINUS 36 TO 36 DEGREE COLD CORE DRIVES SOUTH INTO THE
NORTHERN ROCKIES AND HIGH PLAINS. FAIRLY STRONG WEST WINDS
ALOFT...DECENT MOISTURE AND THE LEFT EXIT REGION OF A STRONG JET
ARE TIMED OVER THE FORECAST AREA MONDAY AND MONDAY NIGHT...WITH
THE EC BEING STRONGEST WITH THESE FEATURES. HAVE INCREASED THE
CLOUD COVER ACROSS THE AREA AND INCREASED THE CHANCE OF PRECIP
IN THE SUN NIGHT THRU TUESDAY TIME FRAME.

TUESDAY AND WEDNESDAY...THE MODEL CONSENSUS CLOSES OFF A TIGHT
500 MB LOW OVER THE WESTERN GREAT BASIN THEN RETROGRADES IT JUST
OFF THE SOUTHERN CA COAST. DEFORMATION ZONE CLOUDS WITH LESSENING
PRECIPITATION CHANCES REMAIN OVER THE AREA TUE AND WED.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY EVENING)
ISSUED AT 945 PM MST WED DEC 24 2014

SNOW AND LOW CLOUD CEILINGS WILL CONTINUE NORTH OF I-70 OBSCURING
NORTHERN MTN TOPS. SNOW WILL SPREAD ACROSS THE REMAINDER OF EASTERN
UTAH AND WESTERN COLORADO VALLEYS BEFORE 15Z RESULTING IN PERIODS
OF IFR CIGS AND VSBY THROUGHOUT THE REMAINDER OF THE PERIOD. ALL
MOUNTAINS WILL BE OBSCURED AT TIMES IN CLOUD AND SNOW.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 6 PM MST FRIDAY FOR COZ001-002.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST FRIDAY NIGHT FOR
     COZ003-004-008>010-012>014-017>019.

     WINTER WEATHER ADVISORY FROM NOON TODAY TO MIDNIGHT MST FRIDAY
     NIGHT FOR COZ023.

UT...WINTER WEATHER ADVISORY UNTIL 6 PM MST FRIDAY FOR UTZ023-025.

&&

$$

SHORT TERM...JOE
LONG TERM...CC
AVIATION...JOE



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