Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 091904
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1204 PM MST Tue Jan 9 2018

.UPDATE...
Issued at 1145 AM MST Tue Jan 9 2018

Previous forecast on track. Made minor adjustments to winds and
sky. Also updated temps to reflect current observations.

&&

.SHORT TERM...(Today and tonight)
Issued at 417 AM MST Tue Jan 9 2018

Satellite and radar imagery shows mid level moisture and a few
showers streaming northeast into the mountains, but most of the
accumulating precipitation is being wrung out before it reaches
our forecast area. Still expect a few light showers to survive
into the Front Range mountains today, but don`t expect much if any
accumulation. Areas north of Rabbit Ears Pass could see a couple
inches of wet snow, where southwesterly flow provides more
favorable orographics.

Meanwhile, the plains will see mild conditions with downslope flow
and more sunshine than yesterday. Still expect a few passing
clouds but sufficient downslope and shallower inversions will
allow high temperatures to push well into the 60s in most
locations. A couple spots including downtown Denver could approach
70F given 700 mb temps near 4-5C and sufficient downslope.

For tonight, mild conditions will persist. The advancing storm
system will bring increasing Q-G lift and a destabilizing airmass.
Most of our terrain is still blocked by southwest flow aloft, but
again locations north of Rabbit Ears will still see favorable
orographics. We`ll begin a Winter Weather Advisory there at
midnight. That advisory will continue and expand eastward on
Wednesday to the Front Range mountains...see Long Term section
below.

.LONG TERM...(Wednesday through Monday)
Issued at 417 AM MST Tue Jan 9 2018

The upper level low currently moving onshore over southern
California is forecast to track across the desert southwest today
and be located near the Four Corners region by 5 AM tomorrow
morning. The moisture ahead of the approaching storm system will
begin producing snowfall in the northern and central mountains by
sunrise. This will continue through the day and extend out over
the plains. Mountain areas could pick up between 4 and 8 inches of
new snow, with higher peaks receiving up to 10 inches. The Winter
Weather Advisory will remain in effect until midnight. Precipitation
on the plains will be in the form of rain due to the warm airmass
that results from the persistent southwesterly flow over Colorado
today and tomorrow. As the upper low moves eastward from the Four
Corners area tomorrow, it will be inducing surface pressure falls
over southeast Colorado. As the surface cyclogenesis continues
into the evening, a strong cold front will move across northeast
Colorado, bringing much colder temperatures and gusty north winds.
The arrival of the cold air will switch precipitation on the
plains over to snow, but will then bring an end to the
precipitation before producing much accumulation near the
foothills. Areas further to the east may see up to an inch or two
of snow by Thursday morning.

From Thursday through Friday, the mountains will continue to see
scattered orographic snow showers as the flow aloft switches to
northwesterly. The plains will be dry and cooler. There are some
indications that a short wave impulse embedded in the
northwesterly flow will cross the state Friday which will kick off
a new round of snow showers in the mountains. After that, the
ECMWF shows the western U.S. upper ridge amplifying, which will
dry out the weather across Colorado. This will also warm the
temperatures a little bit. the next chance of snow for the
mountains is expected Wednesday as the ECMWF show a strong
disturbance moving out of the Pacific Northwest and through the
ridge. All in all, a little more active weather pattern appears to
be getting started that will hopefully begin bringing more
precipitation to our state.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1145 AM MST Tue Jan 9 2018

VFR conditions through the period. Expecting winds to will be
light and variable or north around KDEN through today. Winds
should return back to drainage by 2Z.

A cold front will push across the area late Wednesday afternoon
with gusty north winds, lower ceilings, and rain showers changing
to snow showers before ending in the evening.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 AM Wednesday to midnight MST
Wednesday night for COZ033-034.

Winter Weather Advisory from midnight tonight to midnight MST
Wednesday night for COZ031.

&&

$$

UPDATE...Sullivan
SHORT TERM...Barjenbruch
LONG TERM...Dankers
AVIATION...Sullivan



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