Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 151752

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1052 AM MST Mon Jan 15 2018

Issued at 1050 AM MST Mon Jan 15 2018

Jet induced banded light snowfall sliding southward along the
I-25 corridor now concentrated up against the foothills in
Boulder,Jefferson, Gilpin and Clear Creek counties. This heavier
band is poised to move over southern portions of the corridor/Denver
metro area. Snowfall rates have generally been light, 1/4 to 3/4
inch per hour. Meanwhile, the freezing drizzle has pretty much
ended, except perhaps over the higher reaches of the Palmer Divide
in the lower foothills of Jefferson and Douglas Counties. That too
should end in the next hour or so as the high plains cold air mass
deepens. North of this snow band, skies are quickly clearing as
much drier and colder air spreads down from the north. Dewpoints up
in the corner of the state already in the single digits above and
below zero, setting the stage for the bitter cold night. Next
several hours, should see snowfall and clearing skies shifting
south, however, do not anticipate clearing in the denver metro
area and points south until late afternoon at the earliest. So,
little to no warming today. In the high country, clearing already
well underway. This system really had little impact on areas west
of the Cont Divide,

UPDATE Issued at 648 AM MST Mon Jan 15 2018

Areas of Freezing drizzle refuse to change over to snow
in and around Denver to the Palmer Divide so have issued
a short fuse advisory.  I would think things should change
to all snow by 10 am as colder air continues to spread south into
the area.


.SHORT TERM...(Today and tonight)
Issued at 304 AM MST Mon Jan 15 2018

NW to SE band of light snow continues over the plains early this
morning in association with an upper level jet and upslope
component.  Platteville profiler shows upslope component is rather
shallow but it should be enough to allow for pcpn to spread
southward and affect the Denver metro area by 11z. Accumulations
will be around an inch but a few spots may see up to 2 inches. As
for the higher terrain areas light snow will focus mainly on the
east facing slopes thru midday.

By aftn moisture will gradually decrease from north to south with
light snow coming to an end.  As cold sfc high pres builds into nern
CO aftn highs will likely stay steady or slow fall.  Readings will
be in the teens to mid 20s with the coldest temps over the far nern

For tonight skies should clear out and with light winds overnight
lows across much of the plains should drop below zero.  Wind Chill
values will likely meet advisory criteria over the far ern areas

.LONG TERM...(Tuesday through Sunday)
Issued at 339 AM MST Mon Jan 15 2018

Fairly strong northerly flow aloft on Tuesday will gradually
decrease becoming weak by Tuesday night as an upper ridge moves
into Colorado. An upper ridge axis is over Colorado Tuesday night
through Wednesday night. There is weak downward vertical velocity
over the forecast area Tuesday through Wednesday night. The low
level winds will be weak all four periods with normal diurnal
patterns expected. For moisture, it will be quite dry Tuesday
through Wednesday night. There is no measurable precipitation on
the QPF fields. No pops. For temperatures, Tuesday`s highs will
warm up 3-6 C over today`s below normal readings. Wednesday`s
highs will be 4-10 C warmer than Tuesday`s. For the later days,
Thursday through Sunday, models keep ridging over the CWA Thursday
into Friday. Strong southwesterly flow aloft will be in place
Friday night into Saturday morning. An upper trough is progged to
move across Colorado later Saturday and Saturday night. The GFS is
about a half a period quicker with this feature than is the
ECMWF. Upper ridging moves in later on Sunday and Sunday night.
There is measurable precipitation on both the GFS and ECMWF
Saturday into Sunday morning. It doesn`t look like a big storm.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1050 AM MST Mon Jan 15 2018

LIFR conditions at Denver area airports at present time will
gradually improve from north to south through the afternoon.
The northern or back edge of the precipitation, all snow now,
should reach northern portions of the metro area in the next 1-2
hours. That includes KDEN and KBJC. And, another hour after that
at KAPA. Remaining snowfall should be light and any additional
accumulation should be less 3/4 inch at KDEN and KBJC and no more
than a 1 1/2 inches at KAPA. Visibilities with the snow and fog
will range from 1-3 miles. From 21z to 00z/Tue, all metro
airports should go MVFR with cigs 3000-4000 ft AGL, then VFR
after 00z/Tue with clearing skies. East-northeast winds of 8-15
kts will prevail through 21z, then southeast 6-12kts until 01z,
then drainage at under 10kts overnight.


Wind Chill Advisory from 11 PM this evening to 9 AM MST Tuesday
for COZ048>051.

Winter Weather Advisory until 1 PM MST this afternoon for



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