Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 041749
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1049 AM MST Mon Dec 4 2017

.UPDATE...
Issued at 1045 AM MST Mon Dec 4 2017

Have decreased the pops slightly for the rest of the morning and
into the afternoon for our northern foothills and high mountain
areas with the system pushing south as well as the moderate to
strong downward QG motion and downsloping effects accounted for.
Winds over the plains have turned slightly more north-
northeasterly faster than forecasted, this may end up bring a
brief period of isolated upslope snow showers to the southern
foothills - as advertised by the RAP and HRRR.

Snow over the mountains is decreasing with winds as well, will
allow the Winter Weather Advisory to go through noon as issued. Winds
continue to be the main impact over the eastern plains, with
gusts of 30 to 50 mph expected to continue over the next few hours
before trending downward.

&&

.SHORT TERM...(Today and tonight)
Issued at 413 AM MST Mon Dec 4 2017

Upper trough passing over Colorado this morning. Westerly winds
have increased ahead of the cold front now entering southern
Wyoming. Expect winds just below high wind criteria over the
northeast plains during the middle of the day, then decreasing
considerably in the later part of the afternoon as the pressure
surge moves past.

The deeper moisture that produced snow over the mountains
overnight is gone, but there is still a shallow moist unstable
layer with decent winds. Expect a steady but mainly light
orographic snow to continue through mid morning, then as winds
become more northwesterly and lessen, even lighter snow that will
cling to the peaks and possibly over the valleys of Grand/Jackson
counties most of the day. The previous forecast is in pretty good
shape, so only some minor timing adjustments at this time.

.LONG TERM...(Tuesday through Sunday)
Issued at 413 AM MST Mon Dec 4 2017

Little change in the weather pattern over North America for the
upcoming weak with a large upper level ridge along the Pacific
Coast and an upper level low over the Great Lakes to Hudson Bay. A
north to northwest flow aloft will persist over Colorado. This
pattern will leave the state open to cold intrusions from the
north.

For Tuesday and Wednesday, a dry northerly flow aloft will keep
cool air over the region. Highs over northeast Colorado are
expected to be in the upper 30s to lower 40s. Strong surface high
pressure centered over the western U.S. will help produce windy
conditions at times over the higher terrain and across the eastern
plains.

An upper level trough embedded in the northerly flow aloft will
push through the region Thursday. This will help to reinforce the
colder air on Thursday. Models indicate there may be enough
moisture for light snow with this system. Best chance for this
will be over the mountains where orographic lift will help wring
out the moisture. Snowfall amounts at this time look light with
just a few inches possible over the northwest facing slopes.

For Friday and the weekend. The upper level ridge will shift
slightly eastward. This should be enough to nudge the colder air
east of the state. Dry conditions are expected to prevail with
temperatures climbing above normal. If the ridge doesn`t shift
east, cooler air may stay in place or be slow to leave the area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1045 AM MST Mon Dec 4 2017

VFR through Tuesday morning. Winds have become north to northwest
with gusts around 30 knots across the airports. These winds will
now be on the decrease in speed while veering to the northeast by
around 22z. This will allow ceilings to drop to around 7000 feet,
with some possibly lower near the foothills as upslope pattern
sets up. These winds will return to drainage tonight by midnight.
Much less windy day tomorrow.


&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MST today for COZ031-033.

&&

$$

UPDATE...Kriederman
SHORT TERM...Gimmestad
LONG TERM...Meier
AVIATION...Gimmestad



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