Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230402
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
902 PM MST SAT NOV 22 2014

.UPDATE...
ISSUED AT 858 PM MST SAT NOV 22 2014

A QUICK SHOT OF SNOWFALL AHEAD OF THE FRONT CAUSED A QUICK INCH OF
SNOW IN THE TOWN OF VERNAL AND SURROUNDING COMMUNITIES. DO NOT
ANTICIPATE MUCH MORE ACCUMULATION BUT DECIDED TO ISSUE ADVISORY
FOR THAT ZONE AS LOCAL DISPATCH REPORTS NUMEROUS CAR ACCIDENTS
ACROSS THE AREA. THINK IT BETTER TO GET THE WORD OUT FOR THOSE
INDIVIDUALS CONSIDERING DRIVING TONIGHT. NO OTHER CHANGES TO
CURRENT WINTER HIGHLIGHTS.

UPDATE ISSUED AT 725 PM MST SAT NOV 22 2014

THE SURFACE COLD FRONT HAS ENTERED WRN WY AND IS DRAPED DOWN TO
THE SE THROUGH CENTRAL UTAH. A FEW LIGHTNING STRIKES ARE STILL
BEING OBSERVED ALONG THE FRONT BUT THE NUMBER HAS DROPPED
DRAMATICALLY IN THE LAST FEW HOURS. THIS TREND WILL CONTINUE
THROUGH THE EVENING HOURS.  THE RADAR MOSAIC SHOWS WIDESPREAD
PRECIP ACROSS THE CWA THIS EVENING WITH MANY AREAS REPORTING...OR
HAVING REPORTED...SHOWERS OVER THE LAST FEW HOURS.  THIS WILL
CONTINUE AS THE FRONT APPROACHES. BOTH THE HRRR AND NAM12
INITIALIZED WELL AND BRING THE FRONT THROUGH NRN AREAS BY ABOUT
MIDNIGHT...REACHING THE GRAND VALLEY AROUND 0300L AND THEN THE SAN
JUANS BY DAYBREAK. SNOTELS REPORTING A FEW INCHES OF SNOW FOR THE
PARK/GORE RANGES WHILE ONE SNOTEL IN ERN UT REPORTING AROUND 6
INCHES. CURRENT FORECAST CAPTURING CURRENT WEATHER WELL SO MADE NO
CHANGES.

&&

.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 318 PM MST SAT NOV 22 2014

SATELLITE AND ANALYSIS SHOWS THE COLD FRONT OVER NW UT AND
NORTHERN NV ASSOCIATED WITH THE STORM SYSTEM TO MOVE THROUGH THE
AREA TONIGHT. RADAR SHOWS AN AREA OF LOWER CLOUDS AND SCATTERED
SHOWERS MOVING THROUGH CENTRAL CO WITH SOME SHOWERS REPORTED ALONG
INTERSTATE 70 EAST OF GRAND JUNCTION. THE FRONT SHOULD MOVE
THROUGH NORTHWEST CO BY ABOUT MIDNIGHT AND THEN DRAG THROUGH THE
REST OF THE AREA OVERNIGHT. THE BEST COLD ADVECTION AND DYNAMIC
SUPPORT SHOULD MOVE THROUGH BETWEEN ABOUT 04Z AND 12Z. FOLLOWING
FRONTAL PASSAGE...FROM NW TO SE ACROSS THE AREA TONIGHT...WINDS AT
MTN TOP LEVEL WILL SHIFT TO THE NW AND BECOME MORE NORTHERLY WITH
TIME SUNDAY. THIS WILL SHIFT THE FOCUS OF BEST SNOWFALL FROM WEST
TO NNW FACING SLOPES.

MOISTURE STEADILY ERODES SUNDAY...AS FORECAST SOUNDINGS SHOW ONLY
A SHALLOW SURFACE-BASED SATURATED LAYER REMAINING OVER THE
NORTHERN HALF OF THE AREA. TEMPERATURES IN THIS LAYER ARE IN THE
FAVORABLE RANGE FOR DENDRITIC GROWTH WITH A STRONG LAPSE RATE. IN
THESE CONDITIONS OROGRAPHIC SNOWFALL SHOULD CONTINUE IN THE
NORTHERN AND CENTRAL MOUNTAINS...BUT DIMINISH OVER THE VALLEYS AND
PLATEAUS. THE SOUNDING OVER THE SOUTHERN HALF OF THE AREA BECOMES
EVEN DRIER SO THERE A PAUSE IN SNOWFALL SHOULD OCCUR OVER MUCH OF
THE SOUTHERN MOUNTAINS SUNDAY NIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 318 PM MST SAT NOV 22 2014

MONDAY IN NW FLOW A STRONG COLD DISTURBANCE DROPS THROUGH THE
REGION. AN ASSOCIATED -33C COLD CORE STEEPENS LAPSE RATES.
MOISTURE IS LIMITED AND WITH THE JET DIGGING THROUGH UTAH
DYNAMICS ARE NOT OVERLY IMPRESSIVE. BUT COLD ADVECTION...NW
OROGRAPHICS...AND THE SNOW PRODUCTION LAYER AT MTN TOP LEVEL
(-12C AT 700MB) WILL COMBINE TO PRODUCE ANOTHER ROUND OF
SIGNIFICANT SNOWFALL OVER THE NORTHERN AND CENTRAL MTNS. THE
CURRENT HIGHLIGHTS FOR MONDAY LOOK ON TRACK...THOUGH THE NW SAN
JUAN MTNS MAY NEED AN ADVISORY. HAVE RAISED POPS THERE. THE SNOW
SHOULD BE QUITE DRY FOR NOVEMBER...IN THE 20:1 RANGE.

SNOWFALL FINALLY DIMINISHES THROUGH MONDAY NIGHT AS THE TROUGH AND
ASSOCIATED JET SLIDES SE. THE MOIST MARGINALLY UNSTABLE LAYER
SHRINKS TOP DOWN INTO TUESDAY SO SOME SCATTERED SNOW SHOWERS ARE
EXPECTED IN THE EASTERN MTNS THROUGH TUESDAY AFTERNOON WITH LITTLE
ACCUMULATION EXPECTED.

TUESDAY NIGHT THROUGH SATURDAY...THE WEST COAST RIDGE SLOWLY
PROGRESSES INLAND BRINGING DRY CONDITIONS AND PERSISTENT VALLEY
INVERSIONS. UNDERCUT GUIDANCE TEMPERATURES INTO FRIDAY AS THE
RIDGE BUILDS OVER THE FORECAST AREA AND DEAMPLIFIES. THIS PROMISES
DRY CONDITIONS FOR THANKSGIVING. SATURDAY MODEL TIMING BREAKS
SOMEWHAT WITH THE GFS DIGGING THE NEXT TROUGH INTO WA-OR WHILE THE
EC HOLDS IT OFFSHORE. IF THE GFS VERIFIES WE MAY HAVE SHOWERS OVER
THE NORTH BY SUNDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY AFTERNOON)
ISSUED AT 355 PM MST SAT NOV 22 2014

A COLD FRONT WILL CONTINUE MOVING THROUGH THE AREA TONIGHT...
FOLLOWED BY A MOIST NORTHWEST FLOW THROUGH SUNDAY. SNOW IN THE
MOUNTAINS AND A MIX OF RAIN AND SNOW AT LOWER ELEVATIONS WILL
SPREAD FROM NORTHWEST TO SOUTHEAST TONIGHT...CHANGING TO SNOW AT
ALL ELEVATIONS BY ABOUT MIDNIGHT. SNOWFALL IN THE MOUNTAINS WILL
BE HEAVY AT TIMES...AND MOST MOUNTAINS WILL BECOME OBSCURED BY
MIDNIGHT. SNOW LEVELS WILL START AT ABOUT 6500 FEET THIS EVENING
THEN STEADILY DECREASE TO VALLEY BOTTOMS OVERNIGHT AND SUNDAY.

TAF SITES NORTH OF THE SAN JUAN MOUNTAINS WILL EXPERIENCE SHOWERS
THIS EVENING WITH OCCASIONAL IFR CIGS AND VSBYS AFFECTING
KASE...KEGE...KRIL AFTER 03Z AND CONTINUING OVERNIGHT AND SUNDAY.
MVFR CIGS AND VSBYS ARE EXPECTED AT ALL THE OTHER TAF SITES FROM
ABOUT 06Z THROUGH ABOUT 18Z SUNDAY...THEN GRADUALLY DECREASING.
ALSO...STRONG WEST TO NORTHWEST WINDS WILL CAUSE AREAS OF BLOWING
SNOW IN THE MOUNTAINS AND EXPOSED AREAS.

IN ADDITION...STRONG WINDS AT MOUNTAINTOP LEVEL WILL RESULT IN
MODERATE TO STRONG TURBULENCE...ESPECIALLY IN THE LEE OF HIGHER
TERRAIN.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 6 AM MST SUNDAY FOR COZ002-003.

     WINTER WEATHER ADVISORY UNTIL 3 PM MST SUNDAY FOR COZ007-008-011-
     014-018-019.

     WINTER STORM WARNING UNTIL 6 PM MST MONDAY FOR COZ004-005-009-
     010-012-013.

UT...WINTER WEATHER ADVISORY UNTIL 5 AM MST SUNDAY FOR UTZ024.

     WINTER WEATHER ADVISORY UNTIL 6 AM MST SUNDAY FOR UTZ023.

&&

$$

UPDATE...TGR
SHORT TERM...CC
LONG TERM...JOE
AVIATION...CC


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