Area Forecast Discussion
Issued by NWS Grand Junction, CO

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663
FXUS65 KGJT 022346
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
446 PM MST TUE FEB 2 2016

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 356 PM MST TUE FEB 2 2016

STEEP LAPSE RATES...WEAK MID-LEVEL DIVERGENCE OF Q AND MODERATE
NORTH-NORTHWEST FLOW HAS SUSTAINED SNOWFALL OVER THE COLORADO
MOUNTAINS AND ADJACENT VALLEY LOCATIONS DURING THE AFTERNOON.
MODELS INDICATED THIS ACTIVITY WOULD LINGER ALONG THE DIVIDE INTO
THE EVENING. LATER IN THE NIGHT...A SHORTWAVE IN THE NORTH-
NORTHWEST FLOW WILL SUSTAIN AREAS OF SNOW IN THE AFOREMENTIONED
AREA INTO THE MORNING. GIVEN MODEL AGREEMENT...BOOSTED POPS TO
LIKELY FOR THOSE AREAS. MOISTURE AVAILABLE FOR SNOWFALL LIMITED...
SO DO NOT EXPECT MORE THAN 1 TO 2 INCHES...THOUGH HIGHER AMOUNTS
OF LOW DENSITY FLUFF ARE LIKELY ABOVE 10 KFT. ADVECTION OF COLDER
AIR AND FRESH SNOW WILL ALLOW FOR GOOD RADIATIONAL COOLING AND
LOWER THAN NORMAL OVERNIGHT LOWS. PREVIOUS FORECAST UNDERCUT MOS
BY SEVERAL DEGREES WHICH LOOKS REASONABLE IN THIS REGIME...
THEREFORE MADE FEW ADJUSTMENTS.

THE ABOVE MENTIONED WAVE IS SEEN WELL IN THE 1.5 PVU SURFACE
ROTATING ACROSS THE NORTHERN CWA TOMORROW MORNING THEN SWINGING
EAST OF THE DIVIDE BY SUNSET. BEHIND THIS FEATURE WAA TAKES HOLD
AND SHOULD HELP TO TURN OFF THE OROGRAPHIC SNOW MACHINE. DID RAISE
POPS THROUGH EARLY AFTERNOON BEFORE SHOWING A SLOW DOWNWARD TREND
INTO THE EARLY EVENING HOURS. LIGHT ACCUMULATIONS EXPECTED BUT
WITH DRY NATURE OF THE SNOW WE COULD SEE SOME DRIFTING AND BLOWING
SNOW PROBLEMS WITH PASS LEVEL WINDS NEAR 35 MPH FROM THE
NORTHWEST. CONFIDENCE NOT HIGH ABOUT MIXING BEING STRONG ENOUGH TO
SCOUR OUT THE COLD AIR FROM LOWS TOMORROW MORNING. THEREFORE WENT
AHEAD AND LOWERED TEMPERATURES IN THE GUNNISON BASIN...EAGLE
VALLEY AND YAMPA VALLEY. TRANSITORY RIDGING WILL MOVE ACROSS THE
CENTRAL ROCKIES WEDNESDAY NIGHT AS THE NEXT UPSTREAM TROUGH TO
IMPACT THE REGION ARRIVES TO WESTERN UTAH. A SHORT BREAK IN
PRECIPITATION IS EXPECTED OVERNIGHT WITH MAINLY CLEAR SKIES
LEADING TO VERY COLD CONDITIONS.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 356 PM MST TUE FEB 2 2016

MODELS ARE STAYING CONSISTENT BRINGING THE WESTERN UTAH WAVE
ACROSS OUR CWA THURSDAY FOLLOWED BY A RE-ENFORCING WAVE THURSDAY
NIGHT WHICH WILL HELP CARVE OUT THE TROUGH A BIT. ATTM MOISTURE
PROFILES ARE VERY WEEK AND ANY ENSEMBLE DATA POINTING TOWARD
ANOMALOUS CONDITIONS SUGGEST THIS IS COMING THROUGH FAIRLY
MOISTURE STARVED. THE EURO IS THE DRIEST AS A CONSEQUENCE WITH
THIS STORM WHILE THE GFS ON THE WET SIDE. COLD AIR WILL BE IN
PLACE AND CROSS SECTIONS SUGGEST A MOUNTAIN TOP STABLE LAYER
FORMING AHEAD THE WAVE. THIS COULD ENHANCE THE OROGRAPHIC ASPECT
OF THE STORM AND PUSH ACCUMULATING SNOW FARTHER AWAY FROM THE
MOUNTAIN BASES. THE DENDRITIC LAYER IS INCLUDED IN THE PBL AND
THIS WILL HELP WITH SNOW PRODUCTION IN LOWER ELEVATIONS AS WELL.
WEAK CAA BEHIND THIS WAVE IS QUICKLY REPLACED BY WAA FRIDAY
AFTERNOON AS THE NEXT SHORT WAVE RIDGE BUILDS OVERHEAD. BEYOND
THIS THE WEST COAST RIDGE AMPLIFIES SIGNIFICANTLY WHICH DIRECTS
THE PACIFIC MOISTURE SOURCE INTO SOUTHWEST CANADA AND LEAVES A
VERY INDIRECT ROUTE BACK INTO ROCKIES. THE NEXT WAVE DROPPING
OVER THE RIDGE LOOKS TO RIDE MAINLY NORTH OF OUR CWA GOING INTO
THE WEEKEND AND WILL CONTAIN MORE COLD AIR THAN MOISTURE. IT
APPEARS SOME OF THIS COLD AIR WILL BE ABLE TO DROP INTO OUR
NORTHWEST CWA BUT MOST WILL BE STAY EAST OF THE ROCKIES. OVERALL
THE EXTENDED FORECAST LOOKS TO STAY BELOW NORMAL IN THE VALLEYS
DUE TO WEAK INVERSION. AS THE WESTERN RIDGE EXPANDS EASTWARD A BIT
EARLY NEXT WEEK SOME MID SLOPE AREAS SHOULD SEE SOME WARMING.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 432 PM MST TUE FEB 2 2016

NORTHWEST FLOW AT MOUNTAINTOP LEVEL WITH KEEPS AREAS OF OROGRAPHIC
SNOW AND LOW CLOUDS UNTIL ABOUT 06Z. THE MOUNTAINS AND NORTHWEST
CO VALLEYS...ESPECIALLY NORTH AND NORTHWEST FACING SLOPES AND
DRAINAGES WILL BE FAVORED FOR THE BEST SNOWFALL. THAT SAID
SNOWFALL WILL GENERALLY BE ON THE LIGHT SIDE. KASE...KTEX AND KEGE
WILL HAVE PERIODS OF MVFR CIGS AND VSBYS. ALL MOUNTAIN TAF SITES
WILL STAY BELOW ILS BREAKPOINTS. VFR CONDITIONS ARE EXPECTED
ACROSS THE LOWER VALLEYS. MOUNTAIN OBSCURATION WILL BE COMMON.

IMPROVEMENT ACROSS THE ENTIRE CWA IS EXPECTED OVERNIGHT. VFR
CONDITIONS WILL PREVAIL AFTER 12Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&

$$

SHORT TERM...NL/15
LONG TERM...15
AVIATION...CC



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