Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 110411
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
911 PM MST Tue Jan 10 2017

.UPDATE...
Issued at 911 PM MST Tue Jan 10 2017

Radar data from the western Colorado has been showing increasing
coverage through the evening as the next surge of moisture moves
into the state. Web cams from some of the ski area snow stakes
have already shown a couple inches of accumulation this evening,
so don`t see any reason to make any changes to the current
forecasts and warnings. Velocity data on the KFTG radar suggests
60 to 80 mph of flow across the Front Range ridges, so areas up in
the high foothills are probably seeing pretty gusty winds. Will
let the High Wind Warning continue. With the upper level jet over
the state forecast to reach 130+ knots, snow and wind are bound to
result.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM MST Tue Jan 10 2017

The very active and stormy weather pattern continues during the
next 24 hours as a couple of jet streaks transport ribbons of very
moist maritime up over the state. The first of these will dive
down from Idaho overnight with colder air aloft. Models crank out
quite a bit of snow with is feature with strong westerly mid-
slope winds accompanying the jet. marginally unstable lapse rates
should support 1-2 inch per hour snowfall rates on higher west and
north facing slopes...as well as over higher terrain of eastern
Grand and Summit counties. Such a flow would be especially
favorable for the Berthoud pass area where we could see short
periods of 2-3 inch per hour rates. Strong winds overnight into
Wednesday morning also likely to produce considerable blowing and
drifting snow esply on the higher passes and up around the
Eisenhower Tunnel. Models show the next jet streak racing up from
the 4-corners area late tonight and Wednesday morning. This would
favor better snowfall rates over the central mountains...zone 34
during the day. Snow amounts in zone 34 next 24 hours probably not
as much as that expected in mtn areas along and north of the I-70
corridor...but strong west-southwest winds will likely continue
to produce areas of blowing and drifting snow.

Along the east slope of the Front Range...Chinook winds continue
to strengthen but speeds still well under high wind criteria. the
tight cross mtn pressure gradient has yet to material and the mtn
wave is only beginning to show up in pilot reports. Still believe
conditions favorable for very strong downslope winds in the higher
foothills within the next few hours. Overnight...these winds are
expected to be sporadic as it the nature of Chinook...with the
strongest speeds after 06z with mtn top stability increasing due
to warming at mid-level with the approaching southwest jet. The
plains should escape the strong winds but may see a few light
rain showers drift off the foothills from time to time.

On Wednesday...Chinook winds are expected to quickly shut down in
the morning with cooler air slipping down from southeast Wyoming
and Nebraska. The main frontal surge appears to back into the
Denver area around midday with a shift to northeast sfc winds.
Cold air looks shallow and chances for any precip with this surge
appears low. In the high country...strong west-southwest winds
continue with areas of moderate to heavy snowfall making travel
miserable for most. However...models indicate a gradual cut off in
moisture late in the day and a therefore in snowfall intensity
across the high country after piling up anywhere from 10 to 22
inches of snow.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM MST Tue Jan 10 2017

Moisture will continue to decrease in depth Wednesday night in the
mountains as snowfall slowly diminishes overnight. There will
still be gusty winds over the mountains and east slopes during the
night, but probably not high winds. The cold frontal surge which
pushes through the plains Wed afternoon, retrogrades some
overnight due to downslope flow off the mountains. Appears to be
a reinforcing shot of colder air on Thursday over the plains with
some shallow moisture and some stratus expected Thursday afternoon
through Friday morning. The mountains on early Thursday will only
see minimal snowfall as the flow aloft shifts southwest due to
the upper low which digs into Southern California towards the end
of the week. However, snowfall will increase late Thursday afternoon
and night as upper jet core noses into Western Colorado. The
mountain top flow will remain southwest which will favor zone 31.
This will shift the heavier snowfall further south away from the
Northern Mountains.

For this weekend and into early next week will be watching how the
cutoff low moves across the desert southwest and potential track
towards Colorado. Models have been trending further north as the
low tracks into New Mexico and then Northeast into southwest
Kansas late Sunday and Monday. Long range model solutions are
still varied but they have similar ideas. will need to increase
snow chances especially over far East central Colorado but the
bulk of the snowfall still looks to be over Southeast Colorado.
The mountains will get a break this weekend with unfavorable flow
for any heavy snowfall there under a South to Southwest flow
aloft.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 911 PM MST Tue Jan 10 2017

The strong westerly flow aloft continues tonight with drying
downslope winds across the Denver metro area. As the low level
airmass remains fairly well mixed, gusty winds are expected at
times at the various airports. Gusts in the 20 to 30 knot range
will be possible during the windy periods. Cloud heights will be
8000 feet AGL, or higher. No precipitation is expected. More gusty
winds are expected through tomorrow as a trough of low pressure
lies along the Front Range foothills.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 6 AM MST Wednesday for COZ035-036.

Winter Weather Advisory until 5 PM MST Wednesday for COZ034.

Winter Storm Warning until 5 PM MST Wednesday for COZ031-033.

&&

$$

UPDATE...Dankers
SHORT TERM...Baker
LONG TERM...Entrekin
AVIATION...Dankers



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