Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 221656
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
956 AM MST SAT NOV 22 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 411 AM MST SAT NOV 22 2014

HIGH CLOUDS HAVE BEGUN TO MOVE OVER THE NORTHWEST CORNER EARLY THIS
MORNING AHEAD OF THE NEXT STORM SYSTEM. THIS PACIFIC STORM SYSTEM
PROMISES TO BRING A GOOD ROUND OF SNOW TO THE HIGH COUNTRY...AND TO
SOME OF THE HIGHER AND/OR FAVORED VALLEYS. VARIOUS WINTER
HIGHLIGHTS ARE IN EFFECT FOR THIS UPPER LEVEL TROUGH AND ITS
ASSOCIATED COLD FRONT...AND A SECONDARY DISTURBANCE SCHEDULED FOR
MONDAY.

PRECIPITATION WILL SPREAD IN FROM THE NORTHWEST BEGINNING EARLY
TODAY. MOUNTAIN SNOW...AND VALLEY RAIN OR MIXED PRECIPITATION WILL
RAMP UP ACROSS THE NORTH THIS AFTERNOON AHEAD OF THE COLD FRONT
THAT IS TIMED TO REACH THE NORTHWEST CORNER EARLY THIS EVENING.
THIS FRONT WILL THEN REACH THE I-70 CORRIDOR BY AROUND
MIDNIGHT...AND THEN ACROSS THE REMAINDER OF THE FORECAST AREA BY
DAYBREAK SUNDAY. ADDING UPPER LEVEL SUPPORT...THE LEFT EXIT REGION
OF THE UPPER JET WILL BE FAVORABLY POSITIONED OVER THE FORECAST
AREA THIS EVENING AS THE JET DROPS SOUTHEAST-WARD INTO NEW MEXICO.
INSTABILITY WILL INCREASE THIS EVENING AS TROUGH APPROACHES...THEN
WILL REMAIN SIGNIFICANT AS THE 500 MB -32C COLD POOL MOVES OVER
NORTHWEST TO CENTRAL COLORADO ON SUNDAY. IN ADDITION TO THE
DYNAMICS AND INSTABILITY...STRONG WEST THEN NORTHWEST WINDS WILL
SUPPLY FAVORABLE OROGRAPHICS FOR SLOPES AND DRAINAGES FACING THOSE
DIRECTIONS.

SNOW LEVELS WILL START OUT AROUND 6500 FT...THEN LOWER QUICKLY
BEHIND THE FRONT THIS EVENING AND OVERNIGHT. THE HEAVIEST SNOW
WILL BE ASSOCIATED WITH THE FRONT...SO THE MOST ACTIVE REGION WILL
BE OVER THE NORTH INITIALLY AND THEN WILL SHIFT SOUTH AS THE FRONT
PROGRESSES ACROSS THE AREA. LOWER ELEVATIONS SHOULD SEE A LULL
BEHIND THE FRONT. HOWEVER FAVORABLE OROGRAPHICS WILL KEEP SNOW
ACCUMULATING IN MANY LOCATIONS. ALSO WE SHOULD SEE SOME RE-
INTENSIFICATION SUN AFTERNOON AS THE COLD POOL MOVES OVER THE
AREA. BLOWING SNOW WILL BE A FACTOR THIS AFTERNOON THROUGH
SUNDAY AND POSSIBLY BEYOND...ESPECIALLY OVER THE MOUNTAINS WHERE
GUSTS UP TO 45 MPH WILL BE POSSIBLE. WHILE SNOW TAPERS OFF OVER
THE SOUTH AND WEST BY LATE SUNDAY...SNOWFALL WILL CONTINUE OVER
THE NORTHERN AND CENTRAL MOUNTAINS INTO MONDAY. SEE THE LONGTERM
DISCUSSION FOR ADDITIONAL DETAILS.

TEMPERATURES WILL REMAIN ON THE WARM SIDE TODAY IN THE PREFRONTAL
ENVIRONMENT. THE UNSETTLED AIR MASS IN THE HEART OF THE STORM
TONIGHT WILL KEEP NIGHTTIME LOWS FROM PLUMMETING OVERNIGHT.
SUNDAY WILL BE SIGNIFICANTLY COOLER MOST LOCATIONS...WITH THE BEST
COOLING OVER THE MOUNTAINS AND NORTH.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 411 AM MST SAT NOV 22 2014

MODELS FAIRLY CONSISTENT IN INDICATING A DECREASE IN SNOWFALL
SUNDAY EVENING IN RESPONSE TO A TRANSIENT SHORTWAVE RIDGE MOVING
OVER THE AREA. STILL LOOKS AS THOUGH SNOW WILL CEASE OVER THE SAN
JUANS SO WILL ALLOW SNOW AND BLOWING SNOW ADVISORY TO EXPIRE AT
01Z/MONDAY ACROSS COLORADO/S SOUTHERN MOUNTAINS. LATER SUNDAY
NIGHT A FAST MOVING SHORTWAVE TROUGH IN THE NORTHWEST FLOW WILL
CAUSE SNOWFALL TO AGAIN PICK UP OVER THE NORTHERN AND CENTRAL
MOUNTAINS WHICH WILL THEN CONTINUE UNABATED THROUGH MONDAY
AFTERNOON. WINDS WILL CONTINUE TO BE BRISK RESULTING IN LOW
VISIBILITY IN BLOWING SNOW.

SNOWFALL FINALLY BEGINS TO DIMINISH MONDAY NIGHT AS THE DEEP
TROUGH OVER THE SOUTHERN PLAINS STOPS DIGGING AND BEGINS TO
TRANSLATE EASTWARD. THIS ALLOWS FOR SOME WARMING ALOFT AND
DECREASED INSTABILITY OVER THE AREA. HOWEVER...ANOTHER FAST
MOVING SHORTWAVE TROUGH IN THE NORTHWESTERLIES WILL BRING ANOTHER
ROUND OF SNOWFALL TO THE NORTHERN MOUNTAINS TUESDAY INTO TUESDAY
NIGHT THOUGH ADDITIONAL ACCUMULATIONS APPEAR LIGHT.

ECMWF REVERSED ITSELF AT MIDWEEK NOW COMING INTO AGREEMENT WITH
THE GFS40 WHICH INDICATED A FLAT RIDGE OVER THE AREA THROUGH
THANKSGIVING. THIS WILL ALLOW TEMPERATURES TO RETURN TO NEAR
NORMAL FOR THE HOLIDAY WHILE KEEPING SNOW AT BAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 932 AM MST SAT NOV 22 2014

AN APPROACHING WINTER STORM WILL BEGIN TO IMPACT THE AREA THIS
AFTERNOON OVER THE MOUNTAINS OF NE UTAH...THEN SPREAD EAST AND
SOUTH OVER THE NEXT 24 HOURS. CLOUDS WILL INCREASE AND LOWER AS
THE SYSTEM SWEEPS ACROSS NORTHEAST UTAH AND INTO NORTHWEST
COLORADO THIS AFTERNOON AND EVENING.

EXPECT VFR CONDITIONS TO HOLD AT ALL TAF SITES THROUGH 00Z...
THOUGH INCREASING SNOW SHOWERS THIS AFTERNOON WITH CAUSED AREAS OF
MOUNTAIN OBSCURATION IN THE UINTA MTS AND THE MOUNTAINS NORTH OF
INTERSTATE 70.

EXPECT PRECIPITATION TO DEVELOP NORTH OF THE I-70 CORRIDOR AND IN
THE CENTRAL MOUNTAINS AFTER 21Z AND INCREASE THEREAFTER. SNOW
LEVELS WILL START OFF AT ABOUT 6500 FEET. THE COLD FRONT
ASSOCIATED WITH THIS STORM WILL SWEEP RAPIDLY FROM NORTH TO SOUTH
ACROSS THE FORECAST AREA OVERNIGHT CAUSING SNOW LEVELS TO LOWER TO
VALLEY BOTTOMS. MEANWHILE...SNOWFALL WILL BECOME HEAVY...
ESPECIALLY IN THE MOUNTAINS RESULTING IN WIDESPREAD OBSCURATION.

TAF SITES...ESPECIALLY KRIL...KEGE...AND KASE...WILL EXPERIENCE
PERIODS OF IFR VSBY AND CIGS IN SNOW OVERNIGHT THROUGH SUNDAY
MORNING. DEGRADED FLIGHT CONDITIONS WILL HOLD OFF UNTIL AROUND
MIDNIGHT FOR KMTJ AND KTEX. IN CONTRAST...KVEL IS MOST LIKELY TO
BE IMPACTED THIS EVENING WITH FRONTAL PASSAGE WHILE KDRO IS
UNLIKELY TO EXPERIENCE ANY CONDITIONS BELOW VFR DURING THIS
PERIOD.

IN ADDITION...PRE-FRONTAL AND POST-FRONT WINDS WILL RESULT IN
MODERATE TO STRONG TURBULENCE...ESPECIALLY IN THE LEE OF HIGHER
TERRAIN.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 PM MST
     SUNDAY FOR COZ011-014-018-019.

     WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 6 PM MST MONDAY
     FOR COZ004-005-009-010-012-013.

     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM MST
     SUNDAY FOR COZ002-003.

     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM MST
     SUNDAY FOR COZ007-008.

UT...WINTER WEATHER ADVISORY UNTIL 6 AM MST SUNDAY FOR UTZ023.

&&

$$

SHORT TERM...EH
LONG TERM...NL
AVIATION...CC


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