Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 231603
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
903 AM MST TUE DEC 23 2014

.UPDATE...
ISSUED AT 903 AM MST TUE DEC 23 2014

ALLOWED THE LONE REMAINING WINTER STORM WARNING FOR THE NW SAN
JUAN MTNS TO EXPIRE AT 900 AM AS CDOT WEBCAMS, TELLURIDE METAR,
AND A CONVERSATION WITH A CAIC AVALANCHE FORECASTER IN SILVERTON
INDICATED SNOW HAS MOSTLY TAPERED OFF. THE UNCOMPAHGRE GORGE WAS
QUIET WITH JUST LIGHT SNOW/FLURRIES OVER RED MTN PASS.
INTERESTINGLY, LOW CLOUDS AND LIGHT SNOW PERSISTED FROM RED MTN
PASS TO SILVERTON ON THE LEESIDE (SOUTH SIDE) OF THE SAN JUANS IN
THE N-NE FLOW ALOFT. STILL WINDY OVER THE MTNS THOUGH...WITH THE
UPPER JET STILL OVERHEAD.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 334 AM MST TUE DEC 23 2014

THE N-S ORIENTED JET STREAM WEAKENS THROUGH THE DAY AND SLOWLY
SHIFTS EAST. IN BRISK NORTH FLOW OROGRAPHIC SHOWERS WILL CONTINUE
OVER THE COLORADO NORTH FACES TODAY. A FEW MORE INCHES OF SNOW ARE
POSSIBLE IN THE HWY 550/UNCOMPAHGRE GORGE THIS MORNING WHERE A
WINTER STORM WARNING CONTINUES UNTIL 9AM. ONLY SPOTTY LIGHT
ACCUMULATIONS ARE EXPECTED ELSEWHERE. THE LAST SHOWERS END THIS
EARLY EVENING ALONG THE EASTERN-MOST MOUNTAINS.

THEN THE WESTERN RIDGE BUILDS INTO THE NORTHERN ROCKIES ALLOWING
FOR LIGHTER WINDS ALOFT AND CLEAR SKIES. TONIGHT WILL BE THE
COLDEST NIGHT OF THE SEASON SO FAR FOR MANY LOCATIONS. HAVE
UNDERCUT GUIDANCE A FEW DEGREES AND IT MAY GO COLDER YET.
SIGNIFICANTLY LOWERED TEMPERATURES IN THE GUNNISON AND UINTAH
BASINS WHERE STRONG INVERSIONS ARE THE NORM FOR THE WINTER SEASON.
DEWPOINTS LOOK TO FALL WITH THE TEMPERATURES SO FOG IS EXPECTED TO
BE LIMITED TO NEAR WATERWAYS AND PERHAPS IN THE COLD BASIN
BOTTOMS.

WEDNESDAY THE RIDGE BUILDS OVERHEAD. THE FLOW ALOFT BACKS FROM
NORTH TO WEST. HIGHER LEVEL MOISTURE AND CLOUDS INCREASE FROM THE
WEST ON WEDNESDAY KEEPING THE VALLEY INVERSIONS INTACT.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 334 AM MST TUE DEC 23 2014

HAVE ISSUED A WINTER STORM WATCH FOR THE NORTHERN MOUNTAINS AND
PORTIONS OF THE CENTRAL MOUNTAINS OF WESTERN COLORADO AND EASTERN
UTAH FOR CHRISTMAS DAY THROUGH FRIDAY EVENING. THERE IS THE
POTENTIAL FOR SNOW ACCUMULATIONS IN EXCESS OF A FOOT IN THE
MOUNTAINS. SNOW SHOULD ACCUMULATE AT ALL ELEVATIONS AND MAY HAVE
SIGNIFICANT IMPACTS ON TRAVEL OVER ALL THE HIGH MOUNTAIN PASSES ON
CHRISTMAS DAY AND THE DAY AFTER. TRAVEL AT LOWER ELEVATIONS COULD
BECOME DIFFICULT AS WELL.

THE RIDGE OVER THE AREA AT THE BEGINNING OF THE EXTENDED PERIOD IS
EXPECTED TO QUICKLY BREAKDOWN WED NIGHT AS A PROGRESSIVE PACIFIC
TROUGH DIGS INTO THE GREAT BASIN. MIDRANGE MODELS ARE IN GOOD
AGREEMENT WITH TIMING THIS SYSTEM THROUGH EASTERN UT AND WESTERN
CO THURSDAY...CHRISTMAS MORNING...AND THROUGHOUT CHRISTMAS DAY.
BELIEVE THERE IS ABOUT A TWO DAY PERIOD OF SIGNIFICANT SNOWFALL
POTENTIAL BEGINNING AROUND SUNRISE CHRISTMAS MORNING AND
CONTINUING INTO FRIDAY NIGHT.

THE 700 MB WINDS THU MORNING SHOULD BE SW AT ABOUT 25-30 KTS...
WITH GOOD UPLIFT FROM WARM ADVECTION AND JET DYNAMICS AHEAD OF THE
COLD FRONT. MOISTURE SHOULD BE INCREASING AND LOWERING THROUGH THE
THU MORNING...THEN THE COLD FRONT IS PROJECTED TO MOVE THROUGH
THE AREA THU AFTERNOON AND EVENING. 700 MB TEMPS START OFF
WARM...AROUND MINUS 6 DEGREES C THU MORNING...BUT AFTER THE FRONT
PASSES AND WINDS SHIFT TO THE NW...COLD ADVECTION WILL BRING THE
700 MB TEMPS DOWN TO ABOUT MINUS 12 AFTER MIDNIGHT...ABOUT 09Z
FRIDAY MORNING.

SO IT APPEARS THIS STORM WILL SHOW TWO CHARACTERS...THE FIRST
DOMINATED BY WARMER AND STRONGER SW WINDS ALOFT FOR MOST OF
CHRISTMAS DAY...FOLLOWED BY THE SECOND WITH COOLER AND WEAKER NW
WINDS ALOFT THURSDAY NIGHT THROUGH FRIDAY EVENING.

SATURDAY THROUGH MONDAY...THE NORTH TO NORTHWEST OROGRAPHIC FLOW
REMAINING OVER THE AREA WILL CAUSE AREAS OF SNOW SHOWERS TO
LINGER IN THE MOUNTAINS SAT. THEN A BROAD TROUGH AND COLD FRONT IS
PROJECTED TO DROP SOUTH FROM THE NORTHERN ROCKIES AND AFFECT THE
NORTHERN HALF OF THE AREA SUN AND MON. SNOWFALL MAY RETURN TO THE
AREA...ESPECIALLY SUN NIGHT AND MONDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 334 AM MST TUE DEC 23 2014

OCCASIONAL SNOW SHOWERS WILL CONTINUE THE MVFR CIGS AND VSBYS AT
KTEX AND KASE THRU ABOUT 15Z WITH LOW LEVEL WIND SHEAR AFFECTING
KASE AS WELL. THESE CONDITIONS WILL GRADUALLY IMPROVE THROUGH THE
REST OF THE DAY AND TONIGHT AS MOIST ERODES TO THE SOUTH AND EAST.
VFR CONDITIONS WILL PREVAIL AT ALL THE OTHER TAF SITES. THE
NORTHERLY WINDS ALOFT WILL GRADUALLY DECREASE AS WELL...THOUGH
ENOUGH MOISTURE WILL REMAIN IN THE FLOW TO CAUSE SNOW SHOWERS IN
THE COLORADO MOUNTAINS...WITH OCCASIONALLY OBSCURED MOUNTAINS AND
HIGH MOUNTAIN PASSES.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY
     EVENING FOR COZ003-004-009-010-012-013.

UT...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING
     FOR UTZ023.

&&

$$

UPDATE...JAD
SHORT TERM...JOE
LONG TERM...CC
AVIATION...CC


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