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fxus65 kbou 091248 
afdbou

Area forecast discussion
National Weather Service Denver/Boulder Colorado
548 am MST Mon Dec 9 2019

Update...
issued at 547 am MST Mon Dec 9 2019

A few snowbands stretching out over the northern and western
suburbs as well as the northern plains this morning is likely
being induced by a little jet Max as well as surface convergence.
This has disrupted the stratus over the Denver area and against
the Palmer Divide and foothills, making it dissipate earlier than
expected. Though still expect it to reform and persist through the
morning as winds should be weak upslope.

&&

Short term...(today and tonight)
issued at 355 am MST Mon Dec 9 2019

An upper trough will drop southeast across the state this morning,
with moisture levels decreasing. The northwest flow aloft is
favored in our mountains, so having an expiration of the Winter
Weather Advisory in the late morning remains good. Snow will
continue in the high country, with another 1 to 4 inches possible
through the day. Wind gusts up to 40 mph will continue to cause
areas of blowing snow. A cold frontal passage last night pushed
in low stratus up against the foothills and Palmer Divide,
covering parts of the Metro area. The northwesterly surface winds
over the plains will continue to make a clockwise turn into the
foothills, keeping these low clouds in until late morning at
least, with some hints of it lasting into the early afternoon in
the foothills of Boulder and Larimer counties. Some isolated snow
showers will be found over the northern plains early this morning,
but these should drift east and dissipate by sunrise. The rest of
the plains should remain dry, though the areas under the stratus
could end up producing some flurries or light snow showers. A bit
of low level instability looks to form over the Palmer Divide
later this afternoon as surface winds converge over the area, have
added a slight chance of snow showers.

Another jet will push south from the northern rockies tonight to
create some lift, just enough to squeeze out any remaining
moisture in the orographic flow. Have added some light snow
showers over the northern mountains to account for this. Expecting
less than 2 inches over the 12 hours, however winds will increase
with gusts up to 55 mph to cause more blowing snow.

Long term...(tuesday through sunday)
issued at 355 am MST Mon Dec 9 2019

Models are in pretty good agreement with the pattern change that
will take place in the latter part of this week, which could lead
to significant snow and wind in the Colorado mountains Friday into
next weekend.

For Tuesday, we'll see some moderation in temperatures with
westerly flow and warm advection just off the deck. There will
likely be some mountain wave clouds to contend with, and Lee
troughing will be weak. Therefore, valley areas will struggle to
break out of the colder temperatures, while Denver and the
mountains will see highs rebounding closer to normal. Gusty
winds to around 50 mph can be expected over the mountains and
wind prone areas of the foothills, as cross sections shows a
mountain top stable layer and Cross Mountain component of 30-40
knots.

Wednesday should feature continued moderation with mid level warm
advection. However, a backdoor cold front could slip across the
northeast plains keeping temperatures cooler there. Thursday
should see similar conditions. Dry weather will persist Tuesday
through Thursday.

The weather pattern for US will change by Thursday night and Friday
as a powerful 140+ knot jet moves off the Pacific. Ensembles
continue to point toward a plume of high integrated vapor
transport (2-3 standardized anomalies) reaching Colorado. This,
in combination with strong orographics, relatively high 700-500
mb specific humidity levels of 2+ g/kg, and proximity of the
upper level jet should result in a period of significant mountain
snow/blowing snow. There is potential for more periods of
significant snow/blowing snow into Sunday depending on the
evolution of the Pacific jet stream and location/depth of embedded
short waves. The vast majority of the models/ensembles are now
trying to point to another wave late Saturday or Sunday. This one
would bring a better chance of accumulating snow onto the plains
as well, given the expected forcing and return to upslope flow
behind a frontal passage. Until then, we could very likely see
bouts of gusty downslope winds along the Front Range and adjacent
plains. Temperatures will turn colder and drop below normal for
much of next weekend behind the frontal passage.

&&

Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 547 am MST Mon Dec 9 2019

Post frontal northerly winds have veered around to the east-
southeast, forming the low stratus affecting the terminals early
this morning. A snowband over the northern plains and northern and
western suburbs have disrupted the strength of the stratus deck
though and dissipated it, clearing it out of the terminals faster
than thought. Though there's a chance it could reform, most
likely near apa and bjc. If it does, ceilings will be around 1000
feet through about 16z, with the clouds beginning to scatter out
by 18z. Clouds should clear out, with only high clouds after 00z,
with winds returning to drainage tonight.



&&

Bou watches/warnings/advisories...
Winter Weather Advisory until 11 am MST this morning for coz031-
033-034.

&&

$$

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