Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 151715
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1015 AM MST Fri Jan 15 2021

.UPDATE...
Update Issued at 1007 AM MST Fri Jan 15 2021

Very strong north-northwesterly winds continue to blow over the
eastern 2/3rds of the plains this morning. There are have a
number of 60 plus mph gusts noted. Satellite pictures are showing
a pretty extensive area of blowing dust so will go with a warning
for blowing dust in Lincoln and Washington Counties until 2 PM
MST. Satellite pictures are also showing some upper level
cloudiness moving in from the north and northwest. Models show the
strong north- northwesterly flow aloft to decrease over the CWA
starting this afternoon and continuing this evening. Will continue
the High Wind and Red Flag Warnings for the plains for this
afternoon through 00Z.

&&

.SHORT TERM...(Today and tonight)
Issued at 430 AM MST Fri Jan 15 2021

Strong NNW flow aloft will remain over the area today, with a
continuation of very windy conditions, across the higher terrain
and plains. Winds early this morning have been gusting, from 60
to 80 mph above 11000 ft, with a few gusts of 50 to 60 mph over
portions of the far nern plains.

Cross-sections show the best potential for high winds this morning
as an area of mid level descent resides over the area. For the
higher terrain, the strongest winds will stay mostly above 11000
feet with a few gusts up to 80 mph thru late morning. However,
some of the stronger winds may briefly mix down, into the higher
foothills, with a few gusts to 70 mph. Across the plains, winds
just above the boundary layer are forecast to be in the 50-55 kt
range thru midday and then slowly decrease thru the aftn. Thus as
mixing occurs, later this morning, should see gusts from 55 to 70
mph thru early aftn. In addition, there will probably be some
blowing dust as well over the far ern plains. As for highs,
readings will range from 45 to 50 near the foothills with 35 to 40
over the far ern plains.

For tonight, winds will quickly subside early this evening as a weak
upper level trough approaches from the northwest.  This trough will
bring a chc of snow to the nrn mtns late tonight, mainly after 09z.

.LONG TERM...(Saturday through Thursday)
Issued at 430 AM MST Fri Jan 15 2021

Through this weekend we`ll have continued northwest flow aloft
with a few weak embedded short wave troughs. This flow will
eventually weaken as a low develops to our west or southwest by
midweek.

A ribbon of lift will pass over the area Saturday morning,
bringing a good chance of light snow to the mountains. We expect
a bit more wind and mostly virga on the plains, though a few
flurries are possible. By late afternoon the clouds should be
starting to break up, though a shallow moisture layer should
remain upstream of the Front Range with some very light snow
continuing over the ridges into Saturday night. There`s a decent
shot of cold air across the plains that quickly comes and goes.
With enough wind to limit the cooling, we just lowered the low
temperatures a few degrees for Sunday morning.

Behind this wave on Sunday, there`s warm advection aloft and
subsidence but the flow stays strong for a while, and a northerly
jet streak passes over, creating potential for an amplified
mountain wave again. It`s not a real convincing setup, and the
mountaintop level flow is not that strong, but this should result
in some increase in the winds over the mountains and east slopes.
Warming on the plains may be limited by high clouds associated
with the jet and the mountain wave.

There`s another shortwave and cold front Monday, which will bring
another chance of light snow mainly to the mountains. What happens
after that gets more complex as another shortwave is close enough
to get split and carve out a low west or southwest of us about
Tuesday. There`s yet another shortwave that looks to pass north of
us about Wednesday. If these waves are properly positioned in the
models, this leaves us sitting in the middle of a complex pattern.
It should be cooler with fronts Tuesday and probably again
Thursday. We could get snow with the Tuesday front/trough. Then
there`s a threat of weak lift from a developing deformation zone
ahead of the low that could linger through the middle of the week.
This will likely be southwest of our area, but it could
potentially cover the central mountains, and this could slow the
end of any post-frontal upslope snow Monday night into Tuesday.
Right now it looks like the upper level forcing on Thursday will
be mainly northeast and southwest of us, but there should be some
kind of front on the plains again, so there`s potential for a
little lift and/or upslope. In all of this, the low levels on the
plains look to remain pretty dry so the only significant chance of
snow we`ll be showing is behind the trough late Monday and early
Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1007 AM MST Fri Jan 15 2021

The LLWAS sensors at DIA are showing 8-13 knot north winds at the
airport. Will go with stronger north winds at DIA after 18Z. Do
not think any blowing dust/dirt will affect visibilities at this
time, but will keep a close eye out for such an occurrence.

&&

.FIRE WEATHER...
Issued at 944 AM MST Fri Jan 15 2021

Current conditions indicate very strong winds blowing over the
eastern plains at this time.  In addition to this, relative
humidities are expected to fall to 13 to 20 percent. This will
lead to Red Flag conditions over the eastern plains.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 5 PM MST this afternoon for COZ042-044-
046>051.

Red Flag Warning until 5 PM MST this afternoon for COZ242-244-
246>251.

Blowing Dust Warning until 2 PM MST this afternoon for COZ046-
047-049.

&&

$$

UPDATE.........RJK
SHORT TERM.....RPK
LONG TERM......Gimmestad
AVIATION.......RJK
FIRE WEATHER...RJK/RPK


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