Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 220610
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1110 PM MST SUN DEC 21 2014

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 301 PM MST SUN DEC 21 2014

SNOW HAS STARTED ACCUMULATING FOR MUCH OF THE FORECAST AREA AND
WILL CONTINUE THROUGH TOMORROW MORNING WITH OCCASIONAL SHORT-
LIVED LULLS. IN FACT...SNOW STARTED A LITTLE EARLIER THAN
EXPECTED FOR THE SAN JUANS SO BUMPED UP START TIME FOR WARNINGS
AND ADVISORIES IN THAT AREA.

NO CHANGES TO FORECAST THINKING. MOISTURE WILL CONTINUE TO STREAM
OVER THE AREA WITH A FETCH THAT REACHES AS FAR BACK AS HAWAII
WHILE UPPER LEVEL SUPPORT REMAINS FAVORABLE FOR LARGE SCALE LIFT.
INTERESTINGLY...SOUNDINGS FORECAST SOME MIDLEVEL WARM AIR
ADVECTION TAKING PLACE THIS AFTERNOON UP NORTH AND THIS IS BEING
BORNE OUT WITH CRAIG REPORTING TEMPS AT 38F. NORMALLY THIS WOULD
CAUSE SNOW PRODUCTION TO WANE A BIT BUT IF THE SOUNDING IS TO BE
BELIEVED...COLD AIR ADVECTION IS ALREADY OCCURRING SO ANY RAIN IN
THAT AREA WILL QUICKLY SWITCH BACK TO SNOW AS THE SNOW MACHINE
CONTINUES. FORECAST SNOWFALL AMOUNTS REMAIN RELATIVELY UNCHANGED
WITH 12+ INCHES FOR THE NORTHERN AND CENTRAL MOUNTAINS AND
ANYWHERE FROM 5 TO 9 INCHES FOR THE VALLEYS. TRAVEL ALONG
INTERSTATE 70 WILL BE DIFFICULT THIS EVENING AND OVERNIGHT AS SNOW
WILL CONTINUE. WEBCAMS ALREADY SHOWING ACCUMULATING SNOW JUST EAST
OF GLENWOOD SPRINGS SO EXPECT CONDITIONS TO ONLY GET WORSE. MANY
CHAIN LAWS ARE ALREADY IN EFFECT FOR MOUNTAIN SUMMITS.

WIND ADVISORY REMAINS IN EFFECT THOUGH WINDS ARE ONLY GUSTING
IN THE 20 TO 30 MPH RANGE. GO A LITTLE FURTHER NORTH INTO SRN WY
THOUGH AND WINDS ARE HOWLING WITH GUSTS OF 55 MPH BEING REPORTED.
WITH THAT IN MIND WILL KEEP ADVISORY GOING ESPECIALLY SINCE
STRONGEST PORTION OF JET IS STILL APPROACHING.

INTENSITY WILL START DYING DOWN MONDAY AFTERNOON BUT SOME SNOWFALL
WILL KEEP GOING AS FAVORABLE OROGRAPHICS CONTINUE. A COLD FRONT
WILL ALSO DROP DOWN FROM THE NORTH CAUSING NWLY WINDS TO BECOME
MORE NRLY CAUSING SNOWFALL TO REALLY DIE DOWN AND BECOME MORE
SCATTERED AS THE MOISTURE SOURCE GETS CUT OFF. TEMPS WILL ALSO
DROP WITH THE PASSAGE OF THE COLD FRONT.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 301 PM MST SUN DEC 21 2014

THE SLOWLY WEAKENING JET STREAM ORIENTED NORTH TO SOUTH OVER WRN CO
WILL KEEP SCATTERED SNOW OVER THE CO MTNS TUESDAY...FAVORING THE
NORTH SLOPES. THE JET SLIDES EAST TUE NIGHT FOR CLEARING SKIES. HIGH
PRESSURE RIDGING BRINGING DRY WEATHER AND MOSTLY SUNNY SKIES ON
WEDNESDAY. MORNING INVERSIONS WILL BE SLOW TO MIX OUT UNDER STABLE
CONDITIONS AND KNOCKED HIGH TEMPS DOWN A FEW DEGREES ON WEDNESDAY.

THE RIDGE DOESN`T LAST LONG HOWEVER...AS THE NEXT PACIFIC STORM IS
EXPECTED TO PUSH ACROSS WA/OR WEDNESDAY NIGHT AND DRIVE AN UPPER
TROUGH ACROSS THE NORTHERN AND CENTRAL ROCKIES ON CHRISTMAS DAY.
BOTH THE 12Z GFS AND ECMWF SHOW THE TROUGH CROSSING ERN UT/WRN CO AS
AN OPEN WAVE...BUT THE ECMWF BRINGS A BIT MORE ENERGY ACROSS OUR
AREA WHILE THE GFS KEEPS IT MORE TO THE NORTH. WILL CONTINUE TO KEEP
THE BETTER CHANCES OF ACCUMULATING SNOW ACROSS THE CENTRAL AND NRN
CO MTNS ON CHRISTMAS DAY. THIS STORM WILL LIKELY MOVE OUT AS QUICKLY
AS IT MOVED IN WITH MOSTLY DRY BUT COOL CONDITIONS EXPECTED FRIDAY
AND SATURDAY. MODELS SHOW ANOTHER PACIFIC STORM REACHING THE
NORTHWEST COAST SUNDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY MORNING)
ISSUED AT 1100 PM MST SUN DEC 21 2014

THE JET STREAM REMAINS OVER THE FORECAST AREA TONIGHT AND
STRENGTHENS TO OVER 130KTS THIS AFTERNOON. THIS PRODUCES STRONG
WIND SHEAR BELOW MTN TOP LEVEL...EVEN MIXING DOWN TO THE SURFACE
AT TIMES. WIND GUSTS OF 30-50KT ARE POSSIBLE AT ALL AIRPORTS. IF
THE WIND IS NOT GUSTING LOW LEVEL WIND SHEAR WILL LIKELY OCCUR
WITHIN 020 FEET AGL.

SHOWERS WILL CONTINUE OVER MTNS IMPACTING ALL AIRPORTS EAST OF A
LINE FROM KVEL SOUTH TO KDRO. FOR KHDN KSBS KEGE KASE SNOW AND
BLOWING SNOW WILL PRODUCE CIGS AT OR BLO 010 AND VSBY AT OR BLO
1SM. OTHER AIRPORTS WILL HAVE CIGS AT OR BLO 030 WITH SCT -SNRA
OVERNIGHT AND THROUGH MONDAY. MTN OBSCURATIONS WILL CONTINUE IN
CLOUDS AND BLOWING SNOW. CONDITIONS ARE EXPECTED TO IMPROVE FROM
WEST TO EAST MONDAY NIGHT.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 6 PM MST MONDAY FOR COZ003-017-019.

     WINTER STORM WARNING UNTIL MIDNIGHT MST MONDAY NIGHT FOR COZ002-
     004-010-012>014-018.

     WINTER STORM WARNING UNTIL 6 PM MST MONDAY FOR COZ005-007>009.

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

&&

$$

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



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