Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 170326

Area Forecast Discussion
National Weather Service Denver/Boulder CO
826 PM MST Mon Jan 16 2017

Issued at 820 PM MST Mon Jan 16 2017

Only adjustment tonight involved slowing the trend of decreasing
clouds from interstate 70 southward this evening. Should still see
partial clearing developing after 06z, otherwise current grids
looks good.


.SHORT TERM...(This evening through Tuesday)
Issued at 232 PM MST Mon Jan 16 2017

Only a few flurries lingering in the Palmer Divide area this
afternoon and those will gradually taper off through the evening.
Can`t rule out a few showers lingering a bit longer in Park county
where flow does turn a bit more easterly under the shearing trough
and deformation zone. Even there don`t see much threat of any
accumulating snowfall. Skies will gradually clear overnight, and
the boundary layer flow relaxes to normal drainage winds. With
some melting and still relatively high dewpoints in most areas
this afternoon, expect patchy dense fog to develop in the favored
low lying areas, including the high mountain valleys and South
Platte River valley northeast of Denver. Other than patchy morning
fog on Tuesday, look for drier and warmer weather with a return of
warm advection and sun filled skies. Some valleys may be a little
slow to warm so nudged those down a couple degrees, while bumped
up the foothills/higher terrain a couple per amount of warming

.LONG TERM...(Tuesday night through Monday)
Issued at 232 PM MST Mon Jan 16 2017

Tuesday night the Westerly jet stream extends from the Big Bend
of Texas northeast into Arkansas and the Ohio Valley. A Upper
level low is over northern New Mexico putting northeast Colorado
in a dry easterly upper level flow. The entire atmospheric column
is very dry through overnight Thursday into Friday as the mid and
upper level trough slowly migrates east. Flow aloft across
Colorado under the influence of the vertically stacked trough of
low pressure shifts from easterly Tuesday night to northerly by
Thursday evening. In the mountains and across the Plains
temperatures should warm nicely Wednesday and Thursday under the
influence of the departing trough and short wavelength ridge.
Expect temps to warm into the 50s east of the foothills both
Wednesday and Thursday, with mid to upper 30s in the mountains.
Winds should remain light for mid- January standards area-wide
through Thursday.

On Friday the jet stream intensifies off the California Coast
with a 150 kt west-northwest jet coming onshore Saturday evening.
The jet will advect Pacific moisture into Colorado starting
Friday morning with an expected increase in snow showers on the
West facing slopes across Jackson, Grand, and Summit Counties. The
500mb trough axis passes over central Colorado on Friday and
quickly dries us out by early Saturday. With a lack of easterly
upslope flow, do not expect a great chance of precipitation east
of the foothills. The EC is much stronger with the jet, placing CO
in the right entrance region on Sunday. Both the GFS and ECMWF
develop a strong 500 mb low across the four corners region
Saturday morning and moves it into Oklahoma on Sunday. GFS is a
bit stronger and colder with the low compared to the GFS, but
either solution is not favorable for Plains precipitation and
mountains should only see a light snow given weak NW flow across
the mountains. Another aspect both models agree on is that cooling
aloft from the first shortwave trough will drop high temps 10-12
degrees across the Plains on Friday. There is a hint of
precipitation, likely a cold rain for the far east Plains on
Friday but any rain that falls will be light. On Saturday once
the second, much stronger low crosses into the TX/OK panhandles a
cold front will sweep across the Plains Saturday sometime,
resulting in gusty North winds but temperatures likely not
dropping much off of Fridays highs, with low 40s expected. With a
fair amount of moisture return and weak west upslope flow the
mountains should see light snow Friday afternoon and evening with
the first, weaker system and again Saturday evening through Sunday
midday with the second, potentially stronger system.

Sunday evening through Monday models agree that a strong Pacific
storm develops along the West Coast of California. GFS much
faster, further south, and stronger than the ECMWF. The ECMWF
keeps the trough axis over the Pacific and consequently is weaker
and further north with the moisture shield. Will keep low PoPs in
the mountains in the long range and dry across the Plains until
the models get a better handle on the Pacific Storm.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 820 PM MST Mon Jan 16 2017

ILS restrictions with cigs around 5-6kft agl may linger until by
06z then scatter out as drier air translates fm north to south
over the region. Light drainage winds as well, any threat of fog
tonight should hold to the north of KDEN and possibly affect areas
from KLMO to KFNL, KGXY, and KFMM from 09Z-16Z.




SHORT TERM...Barjenbruch
LONG TERM...Schlatter
AVIATION...Cooper is the U.S. government's official web portal to all federal, state and local government web resources and services.