Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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745
FXUS65 KBOU 061733
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1033 AM MST Wed Dec 6 2017

.UPDATE...
Issued at 1002 AM MST Wed Dec 6 2017

Winds increased over the mountains this afternoon. Min
temperatures adjusted to more closely reflect current
observations. Otherwise, previous forecast is on track.

&&

.SHORT TERM...(Today and tonight)
Issued at 156 AM MST Wed Dec 6 2017

A strong and subsident northwesterly flow aloft will be over the
region today. Gusty northerly winds will develop across the
northeast plains in the wake of a cold front that will push
through the Denver area around 16z. Winds gusts generally east of
I-25 will range from 35 to 45 mph this afternoon, which will
elevate the fire danger especially to the north and east of
Denver where the stronger winds will be. No fire weather
highlights however as colder temperatures will only allow for
minimum relative humidities from the mid 30s to mid 40s. There
will be enough moisture to produce some light snow showers over
the higher north facing mountain slopes. Tonight, a strong
northerly flow aloft can be expected as stronger upper level
ridge amplifies along the west coast. Boundary layer winds will
decouple this evening which will allow for the wind to gradually
taper off. Isolated snow showers will be possible over the far
northeast zones this evening, with otherwise partly to mostly
cloudy conditions. In the mountains, isolated to scattered light
snow showers possible over the higher north facing aspects along
with windy conditions above timberline. Otherwise, dry and stable.

.LONG TERM...(Thursday through Tuesday)
Issued at 156 AM MST Wed Dec 6 2017

High amplitude ridge over western North America and a trough over
the east part of the continent will continue to produce a north
to northwest flow aloft over Colorado. Models are in good
agreement that this pattern will persist for the next week to 10
days at least.

It will be a chilly and blustery day Thursday behind a weak short
wave trough exiting the region. Highs across eastern Colorado are
expected to be in the 30s. With a strong surface high over the
Great Basin, breezy/windy conditions are again expected over much
of the area. There should be enough moisture and orographic lift
to produce light snow over the mountains. Still not sure if there
will be enough lift/moisture for light snow/flurries over the
lower elevation. If there is snowfall it is expected to be light
and mainly from Denver south due to an upslope component here.
Lower elevation snow should be less than an inch with a few inches
possible over the mountains.

The ridge axis shifts a little eastward Friday and for the
weekend. This will keep dry air over the state and bring warmer
temperatures. Windy/breezy conditions are likely Friday, but winds
should be weaker this weekend.

The north to northwest flow aloft continues next week. Some
uncertainty exists with regards to temperatures. The GFS shows a
short wave trough reinforcing the cold air for Monday while the
ECMWF has this system much farther east. This is opposite of what
these two models showed yesterday. However, both models show dry
conditions prevailing into early/mid next week. Will keep the
forecast dry with temperatures slightly above seasonal normals.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1002 AM MST Wed Dec 6 2017

VFR conditions expected through the period. As the northwesterly
winds increase through the afternoon, the winds at KBJC and KAPA
should become more north/northeast. Winds should be peaking
around 21Z, especially near KDEN, before decreasing and heading to
drainage beginning around 04Z. There is low confidence on which
direction they will transition to drainage. The current
directions were chosen due to models indicating an inverted
trough along the foothills.

Thursday another system will move in and bring lowering ceilings.
This will bring strong northwest winds and could reduce flight
categories to MVFR in the afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Sullivan
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Sullivan



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