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000
FXUS65 KGJT 041533
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
833 AM MST WED DEC 4 2013

.UPDATE...
ISSUED AT 831 AM MST WED DEC 4 2013

COLD FRONT IS PUSHING THROUGH MONTEZUMA COUNTY IN SW CO THIS
MORNING. RAIN CHANGED TO SNOW AT CORTEZ IN THE LAST HOUR AND TEMPS
DROPPED ABOUT 10 DEGREES. GUSTY WINDS BEHIND THE FRONT...FOR
AREAS OF BLOWING SNOW. HAVE ADDED CO ZONE 21 AS A WINTER WEATHER
ADVISORY UNTIL 6 PM THIS EVENING FOR SNOW AND BLOWING SNOW. ALSO
EXPANDED THE MENTION OF BLOWING SNOW THIS MORNING BASED ON SPOTTER
COMMENTS OF SUCH FROM CRAIG AND DEBEQUE WHERE 2-3 FOOT DRIFTS WERE
ALSO REPORTED.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 458 AM MST WED DEC 4 2013

THE PRESENT STORM SYSTEM WILL CONTINUE TO UNFOLD WITH WIDESPREAD
ACCUMULATING SNOWFALL ACROSS THE AREA THROUGH THIS AFTERNOON.

THE WESTERN PORTION OF THE SURFACE COLD FRONT MADE IT OVER THE
TAVAPUTS PLATEAU LAST EVENING AND INTO THE GRAND VALLEY AND MOAB
AREA. THIS PORTION OF THIS FRONTAL BAND HAS THEN CONTINUED TO
SWING SOUTH AS THE UPPER LEVEL SHORTWAVE DIGS INTO THE GREAT
BASIN. THIS END OF THE FRONT WILL EVENTUALLY SWING AROUND TO MEET
UP WITH THE COLD FRONT THAT HAS DROPPED ALONG THE PLAINS EAST OF
THE MOUNTAINS. IN THE MEAN TIME...GRAND JUNCTION AND CANYONLANDS
AIRPORT/MOAB HAVE EACH RECEIVED AROUND 2-4 INCHES OF SNOW SINCE
AROUND 10 PM LAST NIGHT. AND AT 330 AM MST...RAIN SWITCHED OVER
THE SNOW AT DELTA...AND WINDS BECAME NORTHWEST AT MONTROSE WITH A
16F DEGREE DROP IN TEMPERATURE. SO WE CAN SAFELY SAY THAT THE
FRONT HAS MADE IT THAT FAR...WITH SNOW ONGOING IN MONTROSE...DELTA
AND NUCLA AT 4AM. OTHERWISE THE STORM STILL ON TRACK WITH SNOW
CONTINUING TO SPREAD OVER THE SOUTH THIS MORNING. EXPECT THAT WITH
DAYLIGHT...THE FRONT WILL MAKE BETTER PROGRESS AND SWEEP ACROSS
THE SOUTHEASTERN CORNER OF THE FORECAST AREA BY EARLY TO MID
AFTERNOON.

WHILE THE HEAVIEST SNOW IS ASSOCIATED WITH AND BEHIND THE FRONTAL
BAND...EXPECT SNOW TO REMAIN WIDESPREAD ACROSS THE AREA THROUGH
TODAY. AS THE FRONT MOVES PAST...THE ASSOCIATED UPPER LEVEL
SHORTWAVE TROUGH WILL SWING ACROSS THE AREA THIS AFTERNOON AND
INTO THE EARLY EVENING. THIS WAVE WILL BRING THE FIRST SHOT OF
VERY COLD TEMPS ALOFT...PRODUCING SOME LOW LEVEL INSTABILITY
THROUGH THIS AFTERNOON. ALSO THE POLAR JET WILL CONTINUE TO
STRETCH ACROSS THE AREA WITH THE CORE APPROACHING 140 KTS. IN
ADDITION TO THIS...THE FAVORED DENDRITIC GROWTH REGION WILL BE
SATURATED WITH GOOD LIFT THROUGH THAT LAYER. THEREFORE THE STORM
REMAINS ON TRACK...WITH LITTLE CHANGE TO THE FORECAST. SNOW WILL
CONTINUE TO ACCUMULATE THROUGH TODAY.

MOISTURE BECOMES LESS AVAILABLE BY THIS EVENING...AND THE DYNAMICS
BEGIN TO WANE AS THE AXIS OF THE SHORTWAVE MOVES OFF. ALSO TEMPS
AT THE SURFACE DROP ENOUGH TO INHIBIT INSTABILITY. THEREFORE SNOW
WILL DIMINISH FROM THE NORTHWEST...EVEN BY LATE AFTERNOON. TEMPS
TONIGHT WILL BE QUITE COLD DUE TO COLD AIR ALOFT AND THE FRESH
SNOW COVER...ESPECIALLY IN AREAS THAT WILL SEE SOME CLEARING.
LOWS WILL DROP BELOW ZERO ACROSS MUCH OF THE AREA. EXPECT FOG TO
FORM IN MANY VALLEYS IN THE COLD AIR BEHIND THIS SYSTEM.

THE NEXT SHORTWAVE WILL BRING ANOTHER SHOT OF EVEN COLDER AIR OVER
THE REGION ON THURSDAY. THIS WILL AGAIN RESULT IN SOME INSTABILITY
IN THE LOWER LEVELS...BUT MOISTURE WILL BE LIMITED. EXPECT THAT
SHOWERS WILL AGAIN PICK UP FOR A TIME OVER THE MOUNTAIN AREAS.
ALSO THE FAR SOUTHEAST VALLEYS COULD CONTINUE TO SEE SHOWERS AS
THE BAROCLINIC ZONE REMAINS IN RELATIVELY CLOSE PROXIMITY OVER
NORTH CENTRAL TO NORTHEAST NM. HIGHS WILL REMAIN IN THE DEEP
FREEZE ON THU WITH SINGLE DIGITS AND TEENS FOR HIGHS ACROSS MUCH
OF THE AREA.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 458 AM MST WED DEC 4 2013

SHORT WAVE MOVES DOWNSTREAM THURSDAY NIGHT...MOMENTARILY BRINGING
AN END TO THE LIGHT SNOW. COLD AIR MASS WITH SOME ARCTIC INFLUENCE
WILL COVER MUCH OF THE FORECAST AREA...FRIDAY MORNING MAY BE THE
COLDEST MORNING IN THE LONG TERM PERIOD. SOME LOW LYING STRATUS OR
STRATOCUMULUS MAY KEEP TEMPS FROM PLUMMETING TO COLDER VALUES...BUT
SUBZERO READINGS WILL BE COMMON ACROSS THE NRN HALF AND MOUNTAIN
LOCATIONS.

DEEP LONG WAVE TROUGH REMAINS POSITIONED OVER THE WRN CONUS THAT
WILL BRING ADDITIONAL SHORT WAVE ENERGY TO THE FOUR CORNER STATES
THIS WEEKEND. THE NEXT SHORT WAVE ROTATES THROUGH THE PACIFIC
NORTHWEST AND POTENTIALLY CARVES OUT A CLOSED LOW CIRCULATION OVER
THE FOUR CORNERS WITH SOME FRONTOGENETICAL FORCING. MOISTURE
SOURCE IS CONTINENTAL...BUT 700 MB SPECIFIC HUMIDITIES MAY EXCEED
2 G/KG AND THAT WOULD BE SUFFICIENT FOR MODERATE MOUNTAIN SNOWFALL
AND LIGHT VALLEY ACCUMULATIONS. THE AIR MASS WOULD BE UNSETTLED
AND THE CHARACTER OF THE SNOW WOULD BE MORE SHOWERY IN NATURE.
WHILE THIS SYSTEM LACKS MOISTURE FOR HEAVY SNOWFALL...BUT EXPECT
SOME IMPACT AS ANY SNOWFALL WILL STICK TO ANY ROAD SURFACES GIVEN
THE COLD TEMPERATURES.

MONDAY AND TUESDAY...GREATER UNCERTAINTY THIS TIME PERIOD EXCEPT
THAT INVERSIONS WILL STRENGTHEN. MOUNTAIN TEMPS AND SRN VALLEYS MAY
MODERATE BUT NRN/CENTRAL VALLEYS STAY COLD (THANKS TO THE
EXTENSIVE SNOW COVER). LONG WAVE TROUGH MAY BE MOVING DOWNSTREAM
THAT ALLOWS WARM AIR ALOFT TO SPREAD ACROSS THE FORECAST AREA. THE
GFS KEEPS CYCLONIC NORTHWEST FLOW ACROSS NW COLORADO...AND THAT
WOULD MEAN MORE SNOW/GUSTY WINDS FOR THE PARK/GORE RANGE. NOT
CONFIDENT WITH THIS IDEA AS THE ECMWF SHOWS SHORT WAVE ENERGY WILL
BE OVER THE NRN/CENTRAL PLAINS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 458 AM MST WED DEC 4 2013

WIDESPREAD IFR FROM LOW CIGS/VIS IN SNOW AND FOG THROUGH 15Z THIS
MORNING. COLD FRONT FROM K4BL-KMTJ-KGUC AT 12Z WILL SWEEP ACROSS
THE REMAINDER OF SW COLORADO THIS MORNING. WIDESPREAD 1SM -SN BR
CIGS BLO OVC010 IS EXPECTED WITH THE COLD FRONT. AS THE COLD FRONT
DEPARTS SOUTHWEST COLORADO...IMPROVING CONDITIONS FROM THE
NORTHWEST WITH RISING VIS/CIGS. LOCAL SURFACE WINDS G25KTS MAY
PRODUCE LOCAL BLSN.

AFTER 00Z TONIGHT...AREAS OF -SN WILL CONTINUE OVER THE WRN
COLORADO MOUNTAINS BUT VFR AT TAF SITES EXPECTED. HOWEVER...PATCHY
FOG OR STRATUS IS EXPECTED OVERNIGHT THAT COULD IMPACT TAF SITES
LIKE KEGE AND KASE.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER STORM WARNING UNTIL 6 PM MST THIS EVENING FOR COZ001>008-
     013.

     WINTER STORM WARNING UNTIL 9 AM MST THURSDAY FOR COZ023.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR COZ020-
     021.

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

     WINTER WEATHER ADVISORY UNTIL 9 AM MST THURSDAY FOR COZ022.

UT...WINTER STORM WARNING UNTIL 6 PM MST THIS EVENING FOR UTZ023-025-
     027.

     WINTER STORM WARNING UNTIL 3 PM MST THIS AFTERNOON FOR UTZ024.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR UTZ029.

     WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR UTZ028.

&&

$$

UPDATE...JAD
SHORT TERM...EH
LONG TERM...PF
AVIATION...PF