Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 212227
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
327 PM MST SUN DEC 21 2014

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 1258 PM MST SUN DEC 21 2014

SNOW WILL CONTINUE IN THE MOUNTAINS OVERNIGHT TAPERING OFF
STARTING MONDAY EVENING. UPSTREAM OBS SHOW VISIBILITIES REDUCING
DOWN TO HALF A MILE WITH THE HEAVIER SNOW. CURRENT WARNING
PRODUCTS STILL ON TRACK BUT OVERNIGHT SHIFTS MAY NEED TO RE-ASSESS
END TIMES DUE TO RECENT MODEL RUNS MOVING THE JET OUT SOONER. THE
LINGERING MOISTURE AND OROGRAPHIC FLOW WILL STILL PRODUCE SOME
SNOW SHOWERS OVER THE MOUNTAINS TOMORROW BUT THE INTENSITY WILL
DECREASE. CONTINUING TO URGE TRAVELERS TO USE CAUTION HAS WINDS
OVER THE HIGHER MOUNTAIN PASSES WILL GUST UP TO 60 MPH THIS
EVENING. CONSIDERABLE BLOWING AND DRIFTING SNOW ALONG WITH
VISIBILITIES BELOW A QUARTER OF A MILE WILL OCCUR OVER AREAS SUCH
AS LOVELAND PASS...BERTHOUD PASS AND RABBIT EARS PASS. OTHER WELL
TRAVELED AREAS ALONG I-70 SUCH AS THE TUNNEL WILL ALSO SEE GREATLY
REDUCED VISIBILITIES WITH ICY AND SNOWY ROADWAYS. TRAVELERS ARE
URGED TO USE CAUTION AND DELAY PLANS TO TRAVEL OVER THE MOUNTAINS
THIS EVENING IF AT ALL POSSIBLE.

FOR THE PLAINS DOWNSLOPING WINDS WILL KEEP AREAS ALONG THE
FOOTHILLS 4-5 DEGREES WARMER AND DRY WITH WINDS GUSTING UP TO 60
MPH OVER THE WIND PRONE AREAS. WINDS WILL MOVE TO A MORE NORTHERLY DIRECTION
EARLY TOMORROW MORNING BRINGING COOLER CONDITIONS ALONG WITH A
CHANCE OF SNOW EAST OF I-25. IN ADDITION TO THE INFLUX OF MOISTURE
OVER THE PLAINS THERE IS SOME INSTABILITY SO SOME AREAS COULD HAVE
SOME LIGHT ACCUMULATION...WITH UP TO 2 INCHES POSSIBLE UNDER THE
HEAVIER BANDS. TEMPERATURES FOR TOMORROW WILL BE COOLER WITH HIGHS
ONLY GETTING INTO THE LOWER 40S FOR THE PLAINS AND 20S FOR THE
MOUNTAINS. BOTH THE NAM AND GFS ARE SHOWING INCREASED WINDS OVER
THE NE PLAINS STARTING TOMORROW AFTERNOON. GFS CURRENTLY HAS 65KTS
AT 850 THAT COULD TRANSLATE TO WARNING CRITERIA. WILL CONSULT WITH
THE NEXT SHIFT AND FUTURE MODEL RUNS ON POSSIBLE ISSUANCE.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 1258 PM MST SUN DEC 21 2014

NORTHEAST COLORADO REMAINS UNDER THE INFLUENCE OF A BROAD UPPER
LEVEL TROUGH CENTERED OVER NEBRASKA AND A STRONG AND COLD NWLY
FLOW MONDAY NIGHT. BANDS OF INSTABILITY AND MOISTURE MOVING DOWN
THE WEST SIDE OF THIS TROUGH SHOULD KEEP SKIES MOSTLY
CLOUDY/OVERCAST AND SNOW CHANCES IN THE FORECAST FOR THE HIGH
PLAINS OVERNIGHT. HOWEVER AREAS ALONG THE BASE OF THE FRONT RANGE
MAY ESCAPE FROM ANY SNOWFALL DUE TO THE DRYING EFFECTS OF
DOWNSLOPE FLOW OFF THE FOOTHILLS AND CHEYENNE RIDGE. IN THE HIGH
COUNTRY...SNOWFALL WILL LIKELY CONTINUE OVERNIGHT...WITH MODERATE
SNOWFALL AT TIMES ON THE HIGHER RIDGES AND NORTHWEST FACING SLOPES
ALONG THE CONTINENTAL DIVIDE. GUSTY NORTHWEST WINDS MAY ALSO
CONTINUE TO PRODUCE SOME BLOWING SNOW IN OPEN TERRAIN. WITH
SNOWFALL LETTING UP AFTER MIDNIGHT...THE WINTER STORM WARNING FOR
MTN ZONES 31...33 AND 34 WILL BE ALLOWED TO EXPIRE AT MIDNIGHT
MST. MEANWHILE STRONG NWLY FLOW ALOFT GRADUALLY MIXES DOWNWARD
OVERNIGHT AS COLD ADVECTION INCREASES. BY EARLY TUESDAY MORNING
MODELS INDICATE N-NWLY SFC WINDS GUSTING TO AROUND 40 MPH ACROSS
THE NORTHEAST CORNER OF THE STATE. WITH SEVERAL INCHES OF SNOW
COVERING THE GROUND OUT THAT WAY...GOOD BET WE/LL SEE SOME BLOWING
SNOW.

DURING THE DAY TUESDAY...MODELS SHOW THE UPPER TROUGH TRACKING
SLOWLY NEWRD AWAY FROM COLORADO WITH NLY FLOW OVER THE PLAINS
BECOMING EVEN STRONGER DURING THE DAY. MODEL WIND SPEEDS ACROSS
THE NERN CORNER IN THE 35-50KT RANGE FOR MUCH OF THE DAY.
BLOWING SNOW WILL BE A GOOD BET ESPECIALLY IN OPEN AREAS OF
LOGAN...WASHINGTON...SEDGWICK AND PHILLIPS COUNTIES WHERE SEVERAL
INCHES OF SNOW ON THE GROUND. NO HIGHLIGHTS AT THIS TIME...HOWEVER
A HIGH WIND WARNING MAY BE NECESSARY SHOULD LATER MODEL RUNS
INDICATE EVEN STRONGER WIND SPEEDS. AS FOR SNOWFALL...SHOULD SEE
AN END TO IT BY MORNING AT LOWER ELEVATION AND BY LATE AFTERNOON
IN THE HIGH COUNTRY WITH THE START OF WARMING AND DRYING ALOFT.

ON WEDNESDAY..LARGE UPPER RIDGE OVER THE GREAT BASIN NUDGES EASTWARD
OVER COLORADO CLEARING SKIES AND WARMING TEMPERATURES. COULD SEE AN
8-10DEG F WARMUP IN MOST AREAS ON WEDNESDAY. WEDNESDAY NIGHT UPPER
RIDGE SHIFTS EAST AS THE NEXT IN A SERIES OF LONG WAVE TROUGHS
SWEEPS OVER THE PACIFIC NORTHWEST. LATEST INDICATIONS...AND THEY ARE
IN BETTER AGREEMENT TODAY...SHOW THIS TROUGH TRACKING NEARLY DUE
EAST ACRS THE NORTHERN ROCKIES. MODELS SHOW THE SOUTH SIDE OF
THIS TROUGH BRUSHING NORTHERN COLORADO CHRISTMAS DAY. AS IT DOES
MTNS AND HIGH VALLEYS SHOULD SEE A SHOT OF SNOW AND GUSTY WINDS
WHILE THE PLAINS REMAIN MILD AND DRY WITH GUSTY DOWNSLOPE FLOW
OFF THE FRONT RANGE. AS THE TROUGH PASSES LATE ON THURSDAY...MODELS
SHOW A BAND OF LIGHT PRECIP ASSOCIATED WITH COLD FRONT SLIPPING
SOUTH ACROSS NORTHEAST COLORADO DURING THE EVENING HOURS. SOME
AREAS MAY SEE SNOWFALL...BUT ANY AMOUNTS SHOULD BE LIGHT. BY LATE
THAT NIGHT...DRYING SETS IN ON COLD AND GUSTY NWLY WINDS.

FRIDAY AND SATURDAY LOOK DRY BUT WITH BELOW AVERAGE TEMPERATURES.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z MONDAY LATE AFTERNOON)
ISSUED AT 1258 PM MST SUN DEC 21 2014

VFR THIS AFTERNOON. WINDS WILL CONTINUE TO GUST THROUGH THE PERIOD
WITH POSSIBLE GUSTS UP TO 35 MPH BY 01Z THIS EVENING...THIS COULD
CAUSE CROSSWIND ISSUES AT BOTH DEN AND APA. WINDS WILL SHIFT FROM
A PREDOMINATELY WESTERLY DIRECTION TO A MORE NORTHERLY ONE BY 06Z
BRINGING INCREASED MOISTURE AND CHANCES FOR SNOW FOR THE
AIRPORT...ICING COULD BE AN ISSUE AT THIS TIME. AFTER 01Z CEILINGS
MAY DROP TO BELOW 6OOOFT...DECREASING TO A POSSIBLE 3000FT WITH
THE SNOW AROUND 08Z. MODELS SHOWING IMPROVING CONDITIONS BY 14Z
TOMORROW BUT WINDS WILL STILL BE GUSTING UP TO 20KTS.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL MIDNIGHT MST MONDAY NIGHT FOR
COZ031>034.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST MONDAY NIGHT FOR
COZ030.

&&

$$

SHORT TERM...BOWEN
LONG TERM...BAKER
AVIATION...BOWEN



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