Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230108
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
608 PM MST MON DEC 22 2014

.UPDATE...
ISSUED AT 608 PM MST MON DEC 22 2014

SNOW HAD LARGELY DIMINISHED OVER THE UPPER COLORADO RIVER BASIN
AND ACROSS THE GRAND MESA EARLY THIS EVENING. EXPECT THERE WILL BE
ADDITIONAL SNOW SHOWERS...THOUGH MORE SCATTERED IN NATURE.
THEREFORE...ALLOWED WINTER STORM WARNINGS EXPIRE FOR THOSE AREAS.
ELSEWHERE IN THE MOUNTAINS...SNOW AND WIND WERE MORE PERSISTENT
SO WILL CONTINUE WSW/S AND BLIZZARD WARNINGS THROUGH MIDNIGHT.
STRONG WINDS CONTINUED ACROSS SOUTHWEST COLORADO SO WILL KEEP
ADVISORIES GOING THERE AS WELL.

&&

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 341 PM MST MON DEC 22 2014

SATELLITE WATER VAPOR LOOP SHOWING DARKENING OVER ERN UT/WRN CO
INDICATIVE OF THE UPPER JET CORE MOVING OVERHEAD. PRECIPITATION
HAS TAKEN ON A MORE BANDED APPEARANCE ON GJX RADAR UNDERNEATH THE
JET. THE COLDER AIR IN WY HAS NOT REALLY MADE INROADS INTO WRN CO
AT THE SURFACE BUT MODELS SHOWED IT OCCURRING ALOFT. PRECIPITATION
HAS ALSO BECOME MORE SHOWERY FROM THE RESULTANT CONVECTIVE
INSTABILITY. COMBINED WITH STRONG VERTICAL WIND SHEAR BECAUSE OF
THE UPPER JET...A FEW SHORT-LIVED THUNDERSTORMS HAVE ALSO
OCCURRED. A BRIEF PERIOD OF HAIL WAS OBSERVED AT THE GJT WEATHER
OFFICE FROM ONE OF THE STRONGER CELLS.

NORTHWEST FLOW WAS IN THE PROCESS OF BECOMING NORTH LATE THIS
AFTERNOON AND WILL CONTINUE THAT TREND THIS EVENING AS THE JET
SETS UP OVER THE AREA. BANDED NATURE OF THE PRECIP WILL RESULT IN
MORE VARIABLE SNOW AMOUNTS LATE TODAY WITH SOME AREAS IN
PERSISTENT SNOW AND OTHERS PERHAPS SEEING LITTLE OR NONE.
CANCELED THE WINTER STORM WARNING FOR THE STEAMBOAT SPGS VALLEY
WITH THIS SHIFT IN WINDS...THOUGH SNOW SHOWERS STILL THIS
AFTERNOON WILL BRING SOME LOCAL ACCUMULATIONS. TEMPTED TO DO THE
SAME WITH THE GUNNISON ZONE 14 EXCEPT THAT A CDOT WEBCAM STILL
SHOWED SNOW AND POOR ROAD CONDITIONS OVER CERRO SUMMIT.
OTHERWISE...KEPT THE MOUNTAIN WINTER HIGHLIGHTS AND THE CORTEZ-
PAGOSA WIND ADVISORY INTACT FOR THE TIME BEING. DRIER AIR WAS
ADVECTING IN ONE THE NORTHERLY FLOW...SO THINK THE TREND OF
DECREASING SNOW OVERNIGHT IS STILL GOOD.

THE 12Z MODELS SHOW A 120KT TO 130KT UPPER JET STILL OVER WRN CO
TUE MORNING FOR STILL SOME WIND OVER THE HIGHER PEAKS AND
SCATTERED SNOW MAINLY ON THE NORTH FACING SLOPES OF THE WRN CO
MTNS. THE JET GRADUALLY WEAKENS AS IT SLIDES EAST OF OUR FORECAST
AREA BY TUESDAY EVENING WITH SKIES CLEARING FROM THE WEST. ERN UT
SHOULD HAVE MOSTLY SUNNY SKIES ALL DAY ON TUE. THE CLEARING SKIES
WILL BRING COLDER TEMPERATURES FOR TUE NIGHT.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 341 PM MST MON DEC 22 2014

THE RIDGE AXIS WILL PASS OVERHEAD ON WEDNESDAY FOR A QUIET
WEATHER DAY. THE NEXT LOW PRESSURE TROUGH WILL THEN DROP INTO THE
GREAT BASIN CHRISTMAS EVE AND THEN MOVE OVER THE AREA ON CHRISTMAS
DAY. MODELS ARE IN PRETTY GOOD AGREEMENT IN THE HANDLING OF THIS
STORM...WITH THE ECMWF CONSISTENTLY A LITTLE STRONGER. WHILE THIS
SYSTEM COMES OUT OF THE NORTHWEST...IT SHOULD BE COLDER THAN OUR
PRESENT STORM. HOWEVER IT STILL LOOKS LIKE SNOW LEVELS WILL BE A
CONCERN FOR RAIN OR A RAIN/SNOW MIX IN THE LOWER VALLEYS. SO FOR
NOW A WHITE CHRISTMAS FOR THESE VALLEYS REMAINS IFFY. HOWEVER IT
IS LIKELY THE MOUNTAINS AND HIGHER CENTRAL AND NORTHERN VALLEYS
WILL SEE FRESH ACCUMULATIONS WITH A CHANCE OF SNOW FOR THE MIDDLE
VALLEYS. THE SNOW LEVELS WILL CONTINUE TO BE CHALLENGING.

MODEL SOLUTIONS FOR LATE THIS WEEK THEN QUICKLY DIVERGE AS THE EC
SHOWS A COLD SECONDARY SHOT DROPPING IN AND REINFORCING THE LONGER
WAVE TROUGH OVER OUR FORECAST AREA ON FRIDAY. IF THIS
VERIFIES...THIS COLDER AIR AND THE LINGERING MOISTURE COULD RESULT
IN A BETTER CHANCE OF VALLEY SNOWFALL THU NIGHT INTO FRI. THE GFS
ON THE OTHER HAND SHOWS THE MAIN TROUGH SHIFTING EAST AND
ACTIVITY QUICKLY WINDING DOWN BY LATE THU NIGHT AND FRI. FOR NOW
HAVE KEPT THE BEST POPS ON CHRISTMAS AFTERNOON/EVENING...WITH A
DOWNWARD TREND THROUGH FRI. HOWEVER THE FORECAST WILL HAVE TO BE
WATCHED TO SEE HOW THIS PLAYS OUT.

THE PATTERN REMAINS UNSETTLED INTO EARLY NEXT WEEK. MODELS INDICATE
ANOTHER STORM SYSTEM WILL MOVE OVER THE REGION DURING THE WEEKEND.
HOWEVER TIMING/STRENGTH IS STILL UNCERTAIN DUE TO DIFFERENCES IN
MODEL SOLUTIONS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 341 PM MST MON DEC 22 2014

THE JET STREAM WILL CONTINUE TO STRETCH ACROSS THE AREA FROM THE
NORTH-NORTHWEST THROUGH TONIGHT...BUT WILL BEGIN TO DIMINISH IN
STRENGTH LATER THIS EVENING. THEREFORE STRONG WIND SHEAR BELOW MTN
TOP LEVEL WILL PERSIST...BUT WILL WEAKEN AFTER MIDNIGHT.
ALSO...THE AIR MASS UNDER THE JET HAS BEEN CONDITIONALLY UNSTABLE
WHICH HAS RESULTED IN THE FORMATION OF CONVECTIVE BANDS THIS
AFTERNOON. STRONG WINDS ALOFT HAVE MIXED TO THE SURFACE AT TIMES DUE
TO THE AFTERNOON MIXING AIDED BY THE CONVECTION. EXPECT THIS WILL
CONTINUE UNTIL POSSIBLY 02-03Z IN SOME LOCATIONS WITH GUSTS TO
35-45KT POSSIBLE AT SOME AREA AIRPORTS. IF THE WIND IS NOT
GUSTING...LOW LEVEL WIND SHEAR WILL LIKELY OCCUR WITHIN 020 FEET
AGL.

SNOW SHOWERS WILL CONTINUE OVER MTNS IMPACTING AREA AIRPORTS EAST
OF A LINE FROM KVEL SSE TO KDRO. FOR KHDN KSBS KEGE KASE KGUC...
MVFR/IFR CIGS/VSBY WILL OCCUR AT TIMES IN SNOW AND BLOWING SNOW.
HEAVY RAIN...SNOW PELLETS OR SNOW MAY OCCUR UNDER THE CONVECTIVE
BANDS AT THE LOWER ELEVATIONS RESULTING IN IFR CONDITIONS. MTN
OBSCURATIONS WILL CONTINUE IN CLOUDS AND BLOWING SNOW. CONDITIONS
ARE EXPECTED TO IMPROVE FROM WEST TO EAST AFTER 06Z TONIGHT...BUT
MOUNTAIN SNOW WILL PERSIST INTO TUE MORNING.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...BLIZZARD WARNING UNTIL MIDNIGHT MST TONIGHT FOR COZ003-017>019.

     WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR COZ004-010-
     012>014-018.

     WIND ADVISORY UNTIL 8 PM MST THIS EVENING FOR COZ021>023.

UT...BLIZZARD WARNING UNTIL MIDNIGHT MST TONIGHT FOR UTZ023.

&&

$$

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



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