Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 201711
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1011 AM MST THU NOV 20 2014

.UPDATE...
ISSUED AT 1009 AM MST THU NOV 20 2014

WEAK DISTURBANCE OVER UT WILL MOVE ACROSS WRN CO THIS AFTERNOON.
MAIN IMPACT WILL BE CLOUDS BUT SOME VIRGA OR A FEW LIGHT SNOW
SHOWERS ARE POSSIBLE OVER THE HIGHER PEAKS. NEXT STORM ALONG THE
NRN CALIF COAST STILL EXPECTED TO SPLIT WITH THE MAIN ENERGY
DROPPING ACROSS AZ ON FRI. CURRENT FORECAST LOOKS ON TRACK.

MAIN WEATHER STORY REMAINS THE STORM EXPECTED TO IMPACT THE FORECAST
AREA THIS WEEKEND WITH SIGNFICANT MOUNTAIN SNOW AND WIND POSSIBLE.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 420 AM MST THU NOV 20 2014

THE HIGH PRESSURE RIDGE THAT HAS DOMINATED THE WEST DURING THE
LAST SEVERAL DAYS WILL CONTINUE TO WEAKEN AND SHIFT EAST AS A LOW
PRESSURE TROUGH PASSES OVER OUR FORECAST AREA TODAY. THE SENSIBLE
WEATHER ASSOCIATED WITH THIS WAVE WILL BE LIMITED AS IT WORKS
AGAINST THE UPPER RIDGE. A FEW MOUNTAIN SNOW SHOWERS WILL BE
POSSIBLE THIS AFTERNOON AND EARLY EVENING...OTHERWISE INCREASED
CLOUDS WILL BE THE NORM. FOLLOWING CLOSELY BEHIND THIS WAVE IS THE
NEXT SPLITTING TROUGH THAT WILL MOVE OVER NORTHERN CALIFORNIA
TODAY. THE BASE OF THIS TROUGH WILL THEN DROP INTO SOUTHERN
ARIZONA ON FRIDAY. THE BEST ENERGY/PRECIPITATION WILL STAY SOUTH
OF OUR FORECAST AREA...BUT A FEW AFTERNOON SHOWERS MAY DEVELOP
OVER THE SOUTHERN MOUNTAINS.

HIGH TEMPERATURES SHOULD BE CLOSE TO NORMAL TODAY AND ON FRIDAY.
NIGHTTIME LOWS WILL CONTINUE TO MODERATE DUE TO WEAKER INVERSIONS
AND EXTENSIVE CLOUD COVER.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 420 AM MST THU NOV 20 2014

SPLIT TROUGH PASSES EAST OF THE FORECAST AREA LATE FRIDAY NIGHT
AND MODELS ALL DRY AT SUNRISE SATURDAY MORNING. HOWEVER...APPEARS
DRY WEATHER WILL BE SHORT LIVED AS A MOIST PACIFIC TROUGH PUSHES
INTO THE EASTERN UINTA MOUNTAINS BY MIDDAY SATURDAY. COLD FRONT
ASSOCIATED WITH THIS SYSTEM ARRIVES OVER NORTHEAST UTAH/NORTHWEST
COLORADO LATE IN THE DAY. TEMPERATURES RELATIVELY MILD AHEAD OF
THE FRONT SO SNOW LARGELY CONFINED TO THE MOUNTAINS SATURDAY
AFTERNOON. MOISTURE SPREADS INTO THE NORTHERN AND CENTRAL COLORADO
MOUNTAINS DURING THE AFTERNOON BRINGING LIGHT TO MODERATE SNOWFALL
ACROSS THOSE AREAS.

THE FRONT SWEEPS ACROSS THE AREA SATURDAY NIGHT BRINGING SNOW
LEVELS DOWN TO VALLEY FLOORS. STEEP LAPSE RATES...DEEP MOISTURE...
OROGRAPHIC LIFT AND JET DIVERGENCE FAVOR PERIODS OF MOUNTAIN
SNOWFALL THROUGH SUNDAY AFTERNOON. A BIT OF LULL INDICATED SUNDAY
EVENING...ESPECIALLY OVER THE SOUTHERN MOUNTAINS...BUT MODELS
INDICATED MOIST NORTHWEST FLOW WILL BE REINFORCED MONDAY RESULTING
IN PROLONGED PERIODS OF SNOW OVER THE COLORADO DIVIDE MOUNTAINS
WHICH MAY PERSIST THROUGH TUESDAY NIGHT. ECMWF MOVES OUT OF PHASE
WITH THE GFS WEDNESDAY DROPPING A TROUGH INTO THE PACIFIC
NORTHWEST AND LEAVING THE MOISTURE TAP OPEN ACROSS THE NORTHERN
MOUNTAINS. IN CONTRAST...THE GFS40 DEVELOPS A RIDGE OVER THE WEST
AND MAINTAINS A DRY NORTHWEST FLOW ACROSS THE AREA ON WEDNESDAY.
GIVEN DIFFERENCES DEFERRED TO THE BLENDED MODEL SOLUTION.

TEMPERATURES TURN CONSIDERABLY COLDER BEHIND THE FRONT SUNDAY AND
STAY BELOW NORMAL THROUGH THE COMING WEEK.

THE ANTICIPATED PROLONGED PERIOD OF SNOWFALL SHOULD LEAD TO
SIGNIFICANT SNOWFALL ACCUMULATIONS...ESPECIALLY ACROSS THE
NORTHERN AND CENTRAL COLORADO MOUNTAINS. SINCE THE ACTION DOESN/T
BEGIN UNTIL LATE IN THE FIFTH PERIOD...WILL HOLD OFF ON WATCH FOR
THE TIME BEING. PERHAPS LATER RUNS WILL CLARIFY THE END OF THE
STORM.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1009 AM MST THU NOV 20 2014

HIGH AND SOME MIDLEVEL CLOUDS WILL MOVE ACROSS ERN UT/WRN CO TODAY
ASSOCIATED WITH A WEAKENING UPPER DISTURBANCE...AND SOME VIRGA OR A
ISOLD LIGHT SNOW SHOWER MAY BE NOTED OVER THE HIGHER MTNS THIS
AFTERNOON. SOME CLEARING EXPECTED TONIGHT BETWEEN DISTURBANCES. VFR
CONDITIONS ARE EXPECTED AT ALL TAF SITES THROUGH 18Z FRI.

&&

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

$$

UPDATE...JAD
SHORT TERM...NL/EH
LONG TERM...NL
AVIATION...JAD


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