Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 211055
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
355 AM MST SUN DEC 21 2014

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 355 AM MST SUN DEC 21 2014

THOUGH CONDITIONS ARE RELATIVELY QUIET ACROSS THE FORECAST AREA
EARLY THIS MORNING...PRECIPITATION AND WIND WILL MOVE IN QUICKLY
FROM THE NORTHWEST LATE THIS MORNING. CURRENT SATELLITE AND RADAR
INDICATE THE ONCOMING STORM BARRELING DOWN ON SOUTHERN IDAHO AND
JUST REACHING NORTHERN UTAH. WINDS WILL INCREASE RAPIDLY LATE THIS
MORNING ACROSS NORTHWEST COLORADO AS A 100KT JET STREAK DROPS DOWN
FROM THE NORTH...WHICH PROMPTED THE ISSUANCE OF A WIND ADVISORY
ACROSS NORTHWEST COLORADO FOR THIS AFTERNOON.

VERY HIGH SPEC HUMIDITIES COMBINED WITH IMPRESSIVE DIVERGENCE
ALOFT WILL BE KEY IN PRECIPITATION DEVELOPMENT AND MAINTENANCE
TODAY. HAZARDS LOOK ON TRACK WITH THE LEADING EDGE OF
PRECIPITATION EXPECTED TO BEGIN ACROSS NORTHWEST COLORADO DURING
THE MID MORNING TODAY. ANTICIPATING TRAVEL CONDITIONS ALONG I-70
TO DETERIORATE QUICKLY BY NOON EAST OF GLENWOOD SPRINGS WHERE THE
SNOW LEVEL LINE WILL FLUCTUATE THROUGHOUT THE DAY. INITIAL WAA
DURING THE DAYTIME HOURS WILL CHANGE OVER TO CAA FROM THE
NORTHWEST OVERNIGHT TONIGHT...WHICH WILL BE QUITE NOTICABLE WITH
AN INCREASE IN WINDS FROM THE NORTHWEST AND SNOW EFFICIENCY
BECOMING QUITE HIGH. THE BULLSEYE OF PRECIPITATION SHIFTS SOUTH
TO THE SAN JUAN MTNS OF COLORADO BY MONDAY AS THE UPPER LEVEL JET
DROPS SOUTH. EXPECTING THAT THE GORGE EFFECT FROM OURAY TO RED MTN
COULD END UP QUITE IMPRESSIVE IN NORTHERLY FLOW ON MONDAY. WILL
ALSO NEED TO CONSIDER WIND ADVISORIES FOR MONDAY FOR THE EASTERN
UTAH AND SOUTHWEST COLORADO VALLEYS WITH STRONG WINDS MIXING TO
THE SFC AND DOWNSLOPE EFFECTS AS WELL.

AN UPPER LEVEL LOW CENTERED OVER SOUTH DAKOTA ON MONDAY SUPPORTS
THE MOISTURE FEED CONTINUING THROUGH MONDAY NIGHT. SEE LONG TERM
SECTION FOR END OF STORM EXPECTATIONS.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 355 AM MST SUN DEC 21 2014

SNOW WILL BE WINDING DOWN FROM WEST TO EAST MONDAY NIGHT AS THIS
STORM PULLS OUT INTO THE PLAINS. FLAT RIDGING BUILDS IN BY
TUESDAY AFTERNOON WITH ONLY A FEW SHOWERS LINGERING NEAR THE
DIVIDE WITH DRY CONDITIONS ANTICIPATED TUESDAY NIGHT AND WEDNESDAY
AS THE RIDGE MOVES OVERHEAD.

NEXT STORM REMAINS ON TRACK TO ARRIVE BY EARLY CHRISTMAS DAY AND
THE NEW 06Z GFS COMING IN A LITTLE DEEPER ONCE AGAIN...LEANING
CLOSER TO THE 00Z ECMWF RUN. THE EC HAS BEEN THE MORE
PERSISTENT/CONSISTENT MODEL OVER THE PAST FEW DAYS AND CONFIDENCE
OF ANOTHER ROUND OF SNOW FOR THE HIGH COUNTRY CONTINUES TO GROW.
SOME EVIDENCE THAT THE GFS WILL DIG THIS SYSTEM EVEN MORE BASED ON
TRAJECTORY OF H3 SPEED MAX ON THE BACK SIDE. NO LONGER EXPECT THIS
WAVE TO CLOSE OFF SO THIS WILL LIMIT POTENTIAL SNOWFALL
ACCUMULATIONS FOR OUR AREA...BUT STILL EXPECT SOLID ADVISORY
AMOUNTS IN THE 5 TO 10 INCH RANGE FOR OUR HIGHER MOUNTAINS. FOCUS
SHOULD BE OVER THE NORTHERN AND CENTRAL MOUNTAINS...BUT ANY
ADDITIONAL DIGGING WILL GET THE SAN JUANS GOING AS WELL. THE
VALLEYS ARE ANOTHER BATTLE AND WILL DIVE INTO THOSE DETAILS AS THE
EVENT DRAWS CLOSER. WITH CURRENT STORM...NO PLANS ON INTRODUCING
ANY ADDITIONAL PRODUCTS TO OUR ALREADY COMPLEX WEATHER SITUATION.

DRIER CONDITIONS PUSH BACK IN THURSDAY NIGHT AND FRIDAY WITH A FEW
SNOW SHOWERS LINGERING OVER THE NORTHERN MOUNTAINS IN DIRTY
NORTHWEST FLOW AS WE CLOSE OUT THE WEEK.

TEMPERATURES WILL BE RUNNING IN THE VICINITY OF NORMAL FOR THIS
TIME OF THE YEAR.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 355 AM MST SUN DEC 21 2014

DEEP PACIFIC MOISTURE WILL BE STREAMING INTO EASTERN UTAH AND
WESTERN COLORADO TODAY WITH WIDESPREAD RAIN AND SNOW DEVELOPING
THROUGHOUT THE REGION. CIGS WILL BE DROPPING STEADILY THROUGHOUT
THE MORNING HOURS WITH WIDESPREAD MVFR AND IFR CONDITIONS EXPECTED
FOR MOUNTAIN AND HIGH VALLEY AIRPORTS BY 20Z THIS AFTERNOON. THESE
CONDITIONS PERSIST THROUGH MONDAY. MOUNTAINS WILL REMAIN
OBSCURED THROUGH THE PERIOD. THE EXCEPTION WILL BE ACROSS
SOUTHWEST COLORADO AND SOUTHEAST UTAH WHERE VFR CONDITIONS WILL
LIKELY PREVAIL.

GUSTY NORTHWEST WINDS WILL ALSO BE PRESENT BY THIS AFTERNOON WITH
LOCAL LLWS POSSIBLE AS VALLEYS WILL BE SLOWER TO MIX OUT.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM NOON TODAY TO MIDNIGHT MST MONDAY
     NIGHT FOR COZ014.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO MIDNIGHT MST
     MONDAY NIGHT FOR COZ018.

     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM MST
     MONDAY FOR COZ017-019.

     WINTER STORM WARNING UNTIL MIDNIGHT MST MONDAY NIGHT FOR COZ002-
     010-012.

     WINTER STORM WARNING UNTIL MIDNIGHT MST MONDAY NIGHT FOR COZ004-
     013.

     WIND ADVISORY FROM NOON TODAY TO NOON MST MONDAY FOR COZ001.

     WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 PM MST MONDAY FOR
     COZ003.

     WINTER STORM WARNING FROM NOON TODAY TO 6 PM MST MONDAY FOR
     COZ007>009.

     WINTER STORM WARNING UNTIL 6 PM MST MONDAY FOR COZ005.

UT...WINTER WEATHER ADVISORY UNTIL 6 PM MST MONDAY FOR UTZ023.

&&

$$

SHORT TERM...JAM
LONG TERM...JDC
AVIATION...JDC



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