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000
FXUS65 KGJT 050442
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
942 PM MST WED DEC 4 2013

.UPDATE...
ISSUED AT 613 PM MST WED DEC 4 2013

ALLOWED THE WARNING ALONG THE I-70 CORRIDOR FROM GLENWOOD SPRINGS
EASTWARD TO EXPIRE. REMAINING HIGHLIGHTS WILL STAY IN EFFECT AS
ASPEN...MONTROSE AND SOME POINTS IN BETWEEN CONTINUE TO REPORT
SNOW AT THIS HOUR.  A BUSY DAY!

UPDATE ISSUED AT 514 PM MST WED DEC 4 2013

LOCAL WEBCAMS SHOW SUN PEAKING THROUGH THE CLOUDS OVER SOUTHERN
COLORADO. WEBCAMS FACING NORTH AND WEST OF PAGOSA SPRINGS SHOW
PLENTY OF CLEARING SO DROPPED THE HIGHLIGHTS FOR THOSE TWO AREAS.
REMAINING WARNINGS WILL STAY IN PLACE.

UPDATE ISSUED AT 455 PM MST WED DEC 4 2013

SATELLITE IMAGERY SHOWING DEFINITE CLEARING FROM THE ROAN/TAVAPUTS
NORTH AND ALSO AREAS TO THE W AND SW. WITH THAT IN MIND...DROPPED
THE WARNINGS AND ADVISORIES IN THOSE AREAS. KEPT REMAINING
WARNINGS AND ADVISORIES IN PLACE BUT WILL KEEP AN EYE OUT SINCE
BEST SUPPORT CONTINUES TO SHIFT SOUTHWARD. ANTICIPATE THE
HIGHLIGHTS IN DURANGO AND PAGOSA SPRINGS WILL BE COMING DOWN EARLY
TOO BUT WILL KEEP AN EYE ON SATELLITE AND WEBCAMS BEFORE DOING
ANYTHING.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 341 PM MST WED DEC 4 2013

THE STRONG AND COLD WINTER STORM WILL BE ON ITS WAY OUT TONIGHT AS
THE CORE OF THE 140-150 KT UPPER JET LIFTS AWAY TO THE NORTHEAST.
LOOKS LIKE THE COLD FRONT HAS JUST EXITED ARCHULETA COUNTY TO THE
SOUTHEAST AS TEMPS AT PAGOSA WERE NOW FALLING. HAVE PRUNED SOME MORE
WINTER HIGHLIGHTS AS CLEARING CONTINUES TO WORK IN FROM THE W AND
NW. LEFT THE CO MTNS AND THE CENTRAL AND SOUTHWEST CO VALLEYS UNDER
WINTER WARNINGS/ADVISORIES AS PRECIPITATION IS EXPECTED TO PERSIST
INTO THE EVENING IN THESE AREAS...ALTHOUGH CONCERNED THAT DURANGO
AND PAGOSA ZONES MAY HAVE TROUBLE REACHING CRITERIA.

WHILE SOME CLEARING OBSERVED LATE TODAY IN NW CO AND NE UT...EXPECT
SOME LOW CLOUDS AND PATCHY FOG TO FILL IN MANY OF THESE VALLEYS
LATER TONIGHT AS INVERSIONS SET UP. THE ARCTIC-TINGED AIR WILL
RESULT IN VERY COLD TEMPS TONIGHT AND AGAIN THURSDAY NIGHT. WITH
WIDESPREAD AND FRESH SNOW COVER...DAYTIME RECOVERY ON THURSDAY WILL
BE RESTRICTED AS THE EXTREMELY COLD AIR MASS SETTLES IN. A WEAKER
AND DRIER TROUGH MOVES ACROSS ON THURSDAY FOR A COUPLE INCHES OF
SNOW OVER THE SAN JUANS THURSDAY AFTERNOON/EVENING...WITH A CHANCE OF
SNOW SHOWERS ELSEWHERE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 341 PM MST WED DEC 4 2013

THE DOOR TO THE ARCTIC REMAINS OPEN THROUGH MONDAY. EXPECT BRISK
SHOTS OF FRESH FRIGID AIR AND SOME NEW SNOW. BY TUESDAY A RIDGE
BUILDING OVER THE WEST WILL CUT OFF THE ARCTIC EXPRESS FOR THIS
REGION. SO THEN VALLEY INVERSIONS WILL LIKELY SETUP FOR CONTINUED
FRIGID CONDITIONS.

FRIDAY THE BROAD WESTERN TROUGH IS RELOADING. THE NEXT OPEN
ALASKAN DISTURBANCE IS DIVING DUE SOUTH THROUGH THE PACIFIC NW
AND INTO THE WESTERN GREAT BASIN FRIDAY NIGHT. THIS BACKS THE
UPPER WINDS TO WEST THEN SOUTHWEST. 700MB TEMPERATURE CLIMBS TO
-12/SOUTH AND -16/NORTH...WHILE THE 300-500MB LAYER STARTS TO
COOL. THIS WILL ASSIST WITH SNOWFALL PRODUCTION BY RAISING THE
SNOW PRODUCTION LAYER UP TO THE MTN TOP LAYER AND STEEPENS THE
LAPSE RATE. THE TROUGH PASSAGE OCCURS EARLY SUNDAY MORNING WITH
BEST SNOW ACCUMULATION SHIFTING FRONT SW TO NW (SKI) SLOPES. SNOW
PERSISTS OVER THE NW COLORADO MTNS INTO MONDAY AS THE H5 -40C COLD
CORE BRUSHES THE NORTH. THIS IS IMPRESSIVELY COLD AIR AND WILL
LIKELY SCOUR OUT ANY WEAK INVERSIONS THAT HAVE FORMED. HIGHLIGHTS
ARE QUITE POSSIBLE WITH THIS TROUGH PASSAGE.

BEGINNING MONDAY AFTERNOON THE EASTERN PACIFIC RIDGE PROGRESSES
INLAND SOMEWHAT. THIS BRINGS A QUICK MODIFICATION TO THE COLD MID-
UPPER PORTIONS OF THE ATMOSPHERE. THIS WILL LIKELY LOCK THE SNOW
COVERED VALLEYS INTO WHAT WILL BECOME STRONG AND PERSISTENT
INVERSIONS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 942 PM MST WED DEC 4 2013

SNOW WILL CONTINUE TO WIND DOWN DURING THE NEXT FEW HOURS. HOWEVER
SOME AREAS OF SNOW WILL PERSIST LATE TONIGHT ALONG OROGRAPHICALLY
FAVORED SLOPES AND DRAINAGES. TAF SITES THAT MAY CONTINUE TO SEE
SNOW AT TIMES UNTIL AROUND 09Z...INCLUDE KASE/KMTJ/KTEX. LOCAL
MOUNTAIN OBSCURATIONS WILL ALSO BE EXPECTED. MOUNTAIN SNOW WILL
INCREASE A LITTLE THURSDAY AFTERNOON...05/19Z-06/00Z...AS THE NEXT
WAVE PASSES. IN ADDITION TO THE LINGERING SNOW...PATCHY FOG WILL
FORM IN MANY VALLEY LOCATIONS LATE TONIGHT THROUGH THURSDAY
MORNING...AND MAY IMPACT AREA TAF SITES.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR COZ009>012-
     014-017>019.

UT...NONE.

&&

$$

UPDATE...TGR
SHORT TERM...JAD
LONG TERM...JOE
AVIATION...EH