Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 140850
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
150 AM MST SUN DEC 14 2014

.UPDATE...
ISSUED AT 149 AM MST SUN DEC 14 2014

AS THE FLOW SWITCHES AROUND TO THE NORTHWEST THE FOCUS HAS
SHIFTED TO THE CENTRAL AND NORTHERN PORTION OF THE FORECAST AREA
EARLY THIS MORNING. THEREFORE THE CHANCE FOR PRECIPITATION HAS
DIMINISHED ACROSS SOUTHWEST COLORADO AND SOUTHEAST UTAH. WHILE
THESE AREAS MAY SEE SOME SHOWERS THROUGH THE NEXT FEW HOURS...ANY
ADDITIONAL SNOW WILL BE VERY LIGHT. THEREFORE THE WINTER WEATHER
ADVISORIES FOR UT ZONE 29...AND CO ZONES 21 AND 22 HAVE BEEN
CANCELLED.

THE OTHER CONCERN IS THE DENSE FOG THAT HAS DEVELOPED IN THE FOUR
CORNERS AREA AS OBSERVED AT CORTEZ AND BLANDING. THESE
OBSERVATIONS ALSO HAVE KEEP A ZERO DEGREE DEW POINT DEPRESSION FOR
THE LAST SEVERAL HOURS. THEREFORE THE AIR MASS IS QUITE SATURATED
AND IS EXPECTED TO REMAIN THAT WAY INTO THE DAYLIGHT HOURS.
THEREFORE HAVE ISSUED A DENSE FOG ADVISORY FOR UT ZONE 22 AND CO
ZONE 21 UNTIL 11 AM. THIS MAY BE A BIT LONG IN DURATION...BUT
EXPECT THAT THIS FOG WILL BE SOMEWHAT SLOW TO ERODE.

UPDATE ISSUED AT 1119 PM MST SAT DEC 13 2014

PRECIPITATION ACROSS MANY OF THE MORE WESTERN VALLEYS STILL HAS
NOT SWITCHED OVER TO SNOW WITH TEMPERATURES AROUND 33-34
DEGREES...AND LITTLE IF ANY TEMP/DEWPOINT SPREAD. THE RADAR LOOP
SHOWS THAT THE FLOW HAS SHIFTED FROM SOUTH TO NORTH OVER EASTERN
UT AS THE UPPER TROUGH MOVES OVERHEAD. THE MORE NORTHERLY FLOW
SHOULD RESULT IN SOME COOLING...SO RAIN IS STILL EXPECTED SWITCH
TO SNOW IN THE NEXT COUPLE HOURS AT THESE LAGGING LOCATIONS.
OTHERWISE FORECAST REMAINS ON TRACK.

UPDATE ISSUED AT 622 PM MST SAT DEC 13 2014

WATER VAPOR AND IR IMAGERY SHOWING PLUME OF MOISTURE REMAINING
OVER MUCH OF THE CWA...SLOWLY MOVING EAST. CAIC AND CDOT HAVE
REPORTED UPWARDS OF 3 INCHES AN HOUR OVER PORTIONS OF SAN JUANS
AND WITH SUCH SLOW PROGRESSION OF SAID PLUME...ENHANCED SNOWFALL
WILL LIKELY CONTINUE THROUGH MIDNIGHT. WENT AHEAD AND UPGRADED
ADVISORIES FOR SAN JUANS AND UNCOMPAHGRE PLATEAU TO WARNINGS WITH
12 INCHES LIKELY...SOME LOCAL AMOUNTS POSSIBLY REACHING NEAR 15
INCHES WHEN ALL IS SAID AND DONE. NO OTHER CHANGES AT THIS TIME.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 256 PM MST SAT DEC 13 2014

COLD FRONT CONTINUES TO PUSH SLOWLY EAST ACROSS WESTERN COLORADO
THIS AFTERNOON AND WILL BE EXITING THE FORECAST AREA LATE TONIGHT.
DEEP PACIFIC MOISTURE OUT AHEAD OF THE FRONT IN DIFFLUENT FLOW
WILL KEEP SHOWERS ROLLING INTO THE EVENING HOURS. NEAR STRONGER
CONVECTIVE CELLS...SNOW LEVELS WILL BE DROPPING WITH SNOW OBSERVED
IN GRAND JUNCTION EARLIER THIS AFTERNOON. STILL NO MEASURABLE
AMOUNTS IN THE VALLEY BUT THAT SHOULD CHANGE OVERNIGHT AS WE SEE
OUR MID LEVEL FLOW SWING AROUND TO THE WEST...WITH COLDER AIR
ARRIVING BEHIND THE FRONT. THIS WILL ALSO SHIFT FOCUS OF
OROGRAPHIC SNOWFALL...WHICH CURRENTLY FAVORS SOUTH FACING
SLOPES...MORE TO WESTERN AND EVENTUALLY NORTHWEST FACING SLOPES BY
EARLY SUNDAY MORNING. SOME CONCERN THAT MOISTURE IS ERODING RATHER
QUICKLY ON THE BACK SIDE OF THIS SYSTEM...ALTHOUGH MODELS AND
GUIDANCE PRODUCTS SUGGEST AN INCH OR TWO OF SNOW POSSIBLE INTO THE
LOWER VALLEYS OF WESTERN COLORADO BY EARLY SUNDAY. SINCE WE ARE
STILL RUNNING WITH EARLY SEASON CRITERIA FOR OUR LOWER
VALLEYS...WILL GO AHEAD AND ISSUE A WINTER WEATHER ADVISORY FOR
THOSE LOCATIONS...INCLUDING GRAND JUNCTION AND MONTROSE. FOCUS IS
NOT NECESSARILY ON THE AMOUNT OF SNOW...BUT RATHER THE IMPACT AS
ROADWAYS ICE UP LATER TONIGHT.

SNOW WINDS DOWN FROM WEST TO EAST ON SUNDAY...WITH BULK OF
ACTIVITY FOCUSED ON THE NORTHERN ZONES WITH FLOW ALOFT BECOMING
NORTHWESTERLY. CURRENT HIGHLIGHTS LOOK REASONABLE IN ALL AREAS SO
NO UPGRADES PLANNED AT THIS TIME. AFTER SEVERAL DAYS OF WARM
WEATHER...TEMPS WILL BE DROPPING BACK TO MORE NORMAL VALUES FOR
THE NEXT SEVERAL DAYS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 256 PM MST SAT DEC 13 2014

HEIGHTS ON THE RISE AGAIN ON MONDAY WITH A BREAK BETWEEN
SYSTEMS...AS MODELS DRIVING ANOTHER FAST MOVING WAVE INTO THE
AREA LATE MONDAY NIGHT AND EARLY TUESDAY. THIS ONE LOOKS TO TARGET
THE CENTRAL AND NORTHERN ZONES AND WILL BE WEAKENING AS IT
ENCOUNTERS THE TRANSITORY RIDGE SHIFTING EAST INTO THE PLAINS.
COULD BE A LOW END ADVISORY EVENT ALTHOUGH DURATION WILL BE SHORT
AS IT EXITS BY TUESDAY AFTERNOON. PATTERN REMAINS ACTIVE
THROUGHOUT THE WEEK WITH A SPLITTING SYSTEM PASSING THROUGH THE
GREAT BASIN WEDNESDAY AND THURSDAY...WHICH WILL BRING ANOTHER
ROUND OF RAIN AND SNOW. HOWEVER...BEST ENERGY LOOKS TO DRIVE SOUTH
OF THE FORECAST AREA...SO SIGNIFICANT PRECIPITATION IN NOT
ANTICIPATED WITH THIS WAVE EITHER. ANOTHER RIDGE SLIDES IN FRIDAY
AND SATURDAY. TEMPS WILL REMAIN NEAR SEASONAL NORMS THROUGH THE
PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 1119 PM MST SAT DEC 13 2014

RAIN AND SNOW SHOWERS WILL CONTINUE ACROSS EASTERN UTAH AND
WESTERN COLORADO EARLY SUNDAY MORNING BEHIND YESTERDAY`S COLD
FRONT. SNOW LEVELS WILL CONTINUE TO LOWER AS THE FLOW SWITCHES
AROUND TO NORTHWEST AND WILL DROP TO THE LOWER VALLEY FLOORS BY
AROUND 09Z-10Z. LOCALLY HEAVY SNOW POSSIBLE OVER THE MOUNTAINS
THROUGH 15Z SUNDAY. EXPECT WIDESPREAD MVFR AND IFR
CONDITIONS...ESPECIALLY NEAR SHOWERS...WITH MOUNTAINS OBSCURED.
AREAS OF FOG WILL ALSO BE POSSIBLE BETWEEN UNTIL AROUND 19Z
SUNDAY. SHOWERS END FROM WEST TO EAST LATE SUNDAY AFTERNOON AND
EVENING...WITH VFR CONDITIONS RETURNING TO THE REGION.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 9 AM MST THIS MORNING FOR COZ023.

     DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING FOR COZ021.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR
     COZ001>003-005-007>009-012-014.

     WINTER STORM WARNING UNTIL NOON MST TODAY FOR COZ017>019.

     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR COZ006-011-020.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ004-
     010-013.

UT...WINTER WEATHER ADVISORY UNTIL 9 AM MST THIS MORNING FOR UTZ023-
     025-028.

     DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING FOR UTZ022.

&&

$$

UPDATE...EH
SHORT TERM...JDC
LONG TERM...JDC
AVIATION...EH


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