Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 290945
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
245 AM MST Tue Nov 29 2016

.SHORT TERM...(Today and tonight)
Issued at 245 AM MST Tue Nov 29 2016

North-northwest flow aloft will prevail today around a strong
closed low over the Northern Plains. A tight pressure gradient
will be over eastern Colorado today bringing strong north-
northwest winds. Models showing the airmass will mix with 45 knot
of winds off the surface. Will go with winds gusts to 50 to 55 mph
over the northeast plains. Could see a couple stronger gusts
accompany snow showers, if any form. The northerly winds will
usher in cooler air. Expect highs to range from the mid 30s to
lower 40s over northeast Colorado.

For the mountains, airmass remains moist below 500 mb. The north-
northwest flow aloft isn`t the greatest for orographic snow.
Lapse rate will be generally be 5-7 C/KM over the mountains, so
expect light snow to continue in places through the day. Web
cameras already showing patchy snow with most of the snow
occurring over the higher areas. Will take another look at radar
and web cameras before deciding to either let the advisory and
warning expire or extend them. For additional snowfall, thinking
trace to 3 inches for the mountains. Airmass will dry tonight, so
snowfall is expected to end most places with additional snowfall
being light and less than inch.

.LONG TERM...(Wednesday through Monday)
Issued at 245 AM MST Tue Nov 29 2016

Outer edge of the massive vortex spinning over the upper Midwest
is projected to loss its grip on nern Colorado by Wednesday. And
yet, the area may still be under the influence of a relatively
strong northwest flow aloft...albeit an increasingly drier and
more stable flow. While cloud cover will considerably
less...particularly east of the mtns...temperatures will hardly be
much warmer than what is anticipated today with this flow. As the
Midwest cyclone moves northeast towards Lake Superior...we should
see a steady drop off in winds on Wednesday, although areas
roughly east of a Cheyenne-to-Burlington line will likely continue
to experience gusty nwly winds in the 20-35 mph range for most of
Wednesday...with a reduction in speeds by mid afternoon. Speeds
should remain well below high wind criteria. Meanwhile the high
mtn ridges may also experience gusty nwly winds in the 30-50 mph
range during the morning, then a steady drop off during the
afternoon. Other than a few light orographic snow showers up along
the Continental Divide Wednesday looks dry.

Thursday looks dry on the plains with a weak shortwave ridge
passing overhead. Flow aloft become predominantly westerly in
direction and the same goes for sfc winds on the plains to start
the day. However...models show sfc winds shifting to an east-
northeast component before noon with pressure falls west of the
mtns. Without this wind shift...temperatures on Thursday could
have been several degs above those on Wednesday. As it stands...
temps on the plains may be no different. In the high country...
low and mid-level moisture ushered in by the above mentioned flow
should quickly increase cloud cover through the day and the
likelihood of orographically generated snowfall on ridgetops and
west facing slopes. Do not see much accumulation during this
period as large scale forcing and instability both appear weak.Its
still possible that the higher windward slopes could pick up 2-5
inches of snow by 12z/Friday as mid-level qg ascent is expected to
increase Thursday night in advance of a weak upper trough
slipping down over nrn Utah. Not counting on any of this moisture/
precipitation spreading out onto the plains during this 24 hour
period.

Friday into Saturday...the upper trough referred to above is
progged by a majority of the models to dive over Arizona and
possibly south of the U.S./Mexico border by early Saturday. This
positions the CWA under weak subsidence in the wake of a weak
shortwave trough. The passage of a weak cold front traveling
south with the upper trough is expected to send temperatures
downward as much as 10 deg f on the plains Friday. May even see a
few light snow showers along the Palmer Dvd and in the foothills
with n-nely winds in its wake. There also will be a slight chance
of snow showers in the high country for most of the day with weak
shear and forcing aloft. Highs on Saturday should rebound nicely
with a subsident west-northwesterly flow aloft. Could see max
temps returning to the lower 40s for portions of the I-25 urban
corridor..but not quite as warm farther east.

Looking ahead to the period Sunday through Tuesday...models
show the SW low quickly tracking east over Texas which allows a
large upper ridge to move in over California and Desert SW. At the
same time a powerful 140-160kt jet maxima rounding the bottom of
a Gulf of Alaska trough is forecast to dig southward over the
central Great Basin by late on Sunday. This would potentially set
the stage for big wx changes downstream over Colorado starting
as early as Monday. It`s possible we could see the coldest
temperatures so far this season on Tuesday. Still too early to
know how much snow if any we`ll see...however chances look half
decent on Tuesday with the GFS indicating fairly deep cyclonic
upslope flow and light qpf over and east of the Front Range.
Stay tune.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 245 AM MST Tue Nov 29 2016

Ceilings may drop to around 6000 feet around 18z as north-
northwest winds bring cooler air and moisture into the area.
North-northwest wind gusts to 35 knots will be possible 16z to
23z. Winds will decrease and turn southerly after 00z. Ceilings
will lift by 00z and by 12z skies will be mostly clear.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST early this morning for
COZ033-034.

Winter Storm Warning until 5 AM MST early this morning for
COZ031.

&&

$$

SHORT TERM...Meier
LONG TERM...Baker
AVIATION...Meier



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