Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 180545
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1045 PM MST WED DEC 17 2014

.SHORT TERM...(TONIGHT THROUGH THURSDAY NIGHT)
ISSUED AT 341 PM MST WED DEC 17 2014

ACCUMULATIONS WERE LIGHT IN THE SOUTHERN MTNS TODAY BUT WERE
PICKING UP IN COVERAGE IN THE AFTERNOON. MID AFTERNOON SNOTELS
INDICATED TRACE TO 3 INCH ACCUMULATIONS...WITH ONE INCH REPORTED
IN SILVERTON. RADAR HAS SHOWED SOME SUSTAINED ENHANCEMENT OVER THE
LA SAL MTNS THIS AFTERNOON.

DISORGANIZED SYSTEM IS WORKING THROUGH NORTHERN NEW MEXICO THIS
AFTERNOON WITH WEAK RIDGING EXPECTED OVERNIGHT. THE KEY TO THE
WEATHER IS THE DEEP MOISTURE THAT IS IN PLACE AND WILL REMAIN
OVER THE AREA THROUGH THURSDAY NIGHT. SOME ACCUMULATIONS ARE
EXPECTED OVER THE SOUTHERN- CENTRAL MTNS THIS AFTERNOON SO HAVE
LEFT ADVISORIES IN PLACE INTO THE EARLY MORNING HOURS.

SOUTHERN MTN SNOW WILL CONTINUE ON THURSDAY AS THE NEXT OPEN WAVE
WORKS THROUGH SOUTHERN AZ-NM. SNOW ACCUMULATIONS LOOK TO BE LIGHT
WITH LITTLE IMPACT.

THE MOST IMPACTFUL WEATHER IS EXPECTED TO BE WIDESPREAD FOG
TONIGHT THROUGH THURSDAY NIGHT. MOUNTAIN FOG THIS AFTERNOON WILL
SETTLE INTO MOST VALLEYS OVERNIGHT AND INTO THURSDAY MORNING.
DENSE FOG ADVISORIES MAY BE NEEDED FAVORING THE SOUTH AND CENTRAL
FORECAST AREA. FOG AGAIN IS EXPECTED THURSDAY NIGHT. ALL THIS
MOISTURE KEEPS TEMPERATURES MILD FOR MID DECEMBER.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 341 PM MST WED DEC 17 2014

A TRANSITORY SHORT WAVE RIDGE WORKS ACROSS THE INTERMOUNTAIN WEST TO
THE HIGH PLAINS FRIDAY AND FRIDAY NIGHT...PUSHED ALONG BY THE
ARRIVAL OF THE STRONG PACIFIC JET TO THE NORTHWEST COAST. MOISTURE
PROFILES ARE NOT VERY FAVORABLE FOR SIGNIFICANT SNOW WITH THE BULK
OF THE DENDRITIC LAYER STAYING UNSATURATED. HOWEVER CROSS SECTIONS
SUGGESTS MOISTURE LINGERING NEAR MOUNTAIN TOP LEVEL WHICH COULD LEAD
TO SOME LIGHT SNOW SHOWERS LINGERING AROUND THE NORTHERN MOUNTAINS
DURING THIS TIME FRAME. CONFIDENCE LIKE POPS WILL BE ON THE VERY LOW
SIDE. 300K THETA SURFACES SHOW A STRONG PUSH OF MOISTURE INTO THE
NORTHWEST STATES EARLY THIS WEEKEND...REACHING OUR NORTHERN CWA BY
EARLY SUNDAY MORNING. THE ARRIVAL OF THE MOISTURE WILL COINCIDE WITH
130+KT CORE NOSING INTO NORTHWEST CORNER OF THE CONUS. MUCH OF THE
UPSTREAM TERRAIN WILL BE ALLOWED TO SOAK UP THIS MOISTURE WITH THE
MAIN STORM TRACK AND DYNAMICS STAY JUST TO OUR NORTH THROUGH SUNDAY.
OUR NORTHERN MOUNTAINS DOWN TO NEAR VAIL PASS WILL BE BRUSHED WITH
MOISTURE AND WILL RELY ON INCREASING OROGRAPHICS TO PRODUCE A
PROLONGED PERIOD OF LIGHT SNOW. THE OROGRAPHICS WILL BE
SUPPLEMENTED BY JET DYNAMICS AND A CONSTANT STREAM OF CHANNELIZED
VORTICITY EARLY MONDAY THROUGH TUESDAY AFTERNOON. PRECIPITABLE
WATER INCREASES TO NEAR 0.5 INCHES...WELL ABOVE NORMAL FOR LATE
DECEMBER OVER OUR NORTHERN CWA. THE INCREASE IN LARGE SCALE
ASCENT...MOISTURE AND WINDS ALOFT SHOULD SPREAD SNOW TO A WIDER
AUDIENCE MONDAY INTO TUESDAY. THE ONLY CONCERN WILL BE WARM AIR
MOVING IN ALOFT AND CHANGING THE DENDRITIC AND POSSIBLY THE
OROGRAPHICS MONDAY...BUT BY MONDAY NIGHT ALL INGREDIENTS APPEAR TO
BE THERE FOR SIGNIFICANT SNOW ACROSS NORTHWEST COLORADO AND
PORTIONS OF THE CENTRAL MOUNTAINS. STRONG RIDGING IN THE EAST
PACIFIC AND A DEEP NEGATIVELY TILTED TROUGH IN THE EAST KEEPS
MOIST NORTHWEST FLOW IN PLACE THROUGH MID- WEEK. THE LONGER TERM
MODELS ARE BEGINNING TO CONVERGE ON A HIGH LATITUDE SYSTEM
DROPPING INTO THE INTERMOUNTAIN WEST WHICH COULD BRING WIDESPREAD
PRECIPITATION TO OUR CWA BY IN TIME FOR THE HOLIDAYS. FOR THE MOST
PART TEMPERATURES WILL BE NEAR TO SLIGHTLY BELOW NORMAL DURING
THIS ACTIVE PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1037 PM MST WED DEC 17 2014

EXPECT WIDESPREAD MTN OBSCURATIONS TO CONTINUE OVERNIGHT FROM THE
CENTRAL MOUNTAINS SOUTHWARD. LOWERED CIGS WILL BE COMMON AT MANY
LOCATIONS EITHER DUE TO -SN AND FG OR JUST REDUCED VIS DUE TO BR.
LOCALLY DENSE FOG IS POSSIBLE BY THURS AM BUT CONFIDENCE IS NOT
HIGH ON WHETHER IT WILL AFFECT ANY TAF SITES. FOG IS EXPECTED TO
BREAK BY 19Z THURSDAY...THOUGH DECENT MOISTURE WILL CONTINUE TO
PLAGUE THE REGION THROUGH THURS NIGHT...ALLOWING ISOLATED SHOWERS
TO CONTINUE THROUGHOUT THE DAY. SHOWERS ON THURS WILL REMAIN
MAINLY OVER THE MTNS SO MTN OBSCURATIONS WILL STILL BE COMMON
THROUGHOUT THE DAY.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 3 AM MST THURSDAY FOR COZ009-018-
     019.

UT...NONE.
&&

$$

SHORT TERM...JOE
LONG TERM...15
AVIATION...JAM



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