Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 220343

Area Forecast Discussion
National Weather Service Denver/Boulder CO
843 PM MST Wed Feb 21 2018

Issued at 835 PM MST Wed Feb 21 2018

Only minor adjustments planned for the grids at this time.
Moisture increasing in the mountains of lgt snow developing at
this time. Coverage will gradually increase across the high
country tonight and continue in Thursday. clouds will gradually
increase across the I-25 Corridor and adjacent plains overnight.


.SHORT TERM...(This evening through Thursday)
Issued at 143 PM MST Wed Feb 21 2018

Satellite pictures are showing some cloudiness moving in from the
west. Temperatures are mainly in the 20s over much of the
forecast area at this time. Models show the upper trough moving
east and decreasing overnight as it nears Colorado from the west.
Strong southwesterly flow aloft will continue over the forecast
area tonight and Thursday. There is decent upward vertical
velocity on the QG Omega fields for the CWA tonight and Thursday
morning. In the lower levels southeasterly winds will dominate out
on the eastern two-thirds of the plains tonight into Thursday.
The western plains will have weaker winds with variable directions
tonight and Thursday. Models show moisture increasing this
evening into Thursday. The QPF fields show measurable snowfall
over the mountains this evening and overnight. This continues on
Thursday and there is a tad of measurable snow out on the plains
too. Will keep pops "likely" in the mountains overnight and
Thursday, less over the plains. Accumulations will not be
significant. For temperatures, Thursday`s highs are 2-4 C warmer
than this afternoon`s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 143 PM MST Wed Feb 21 2018

The weather pattern for the upcoming can be characterized by
upper level troughs moving onto the Pacific Northwest coast and
the digging southeast into the Great Basin. These systems then
lift east/northeast across the Central Rockies in a west to
southwest flow aloft.

Subsidence will move over the area Thursday night as an upper
level trough lifts northeast of the Colorado. Low level moisture
lingers over the area through the evening hours and could produce
light snow/flurries over northeast Colorado. There will be a
slightly better chance for snow in mountains. Overall airmass will
be drying so if any snow occurs it will be light.

The next trough moves into the Great Basin Friday and across the
Central Rockies Friday night. This will bring a good chance for
snow to the mountains. At the surface, a low forms over southern
Colorado and moves into Kansas Friday night. This is expected to
produce west/northwest downslope winds along the Front Range. Best
chance for snow will be over the eastern plains, away from the
downslope. Could be enough lift from the jet to over come the
downslope and produce a few short lived snow bands.

Saturday looks to be be dry as northwest subsident flow prevails
over the area behind the exiting trough. Cold air advection will
result in good mixing and produce breezy conditions. By late in
the day, moisture will increase over the mountains ahead of the
next system and may bring light snow.

The next trough is forecast to track across the Great Basin Saturday
night and Colorado on Sunday. Models indicate this system weakens as
it progresses east across the region. At this time, appears the
mountains will see a round of light snow with downslope winds along
the Front Range and eastern plains.

For early next week, the upper level pattern becomes more
amplified across western North America. The next Pacific system
will slowly drop south across the western states. Ridging ahead of
the trough will usher in warmer air for Monday and Tuesday.
Eventually it will weaken and lift east-northeast across Colorado.
Models hinting at this happening Wednesday. Will cool
temperatures and have some pops in the forecast.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 835 PM MST Wed Feb 21 2018

Weak drainage expected overnight then weak northerly winds on
Thursday around 18z. VFR conditions this evening, then ILS
restrictions after 07z, with MVFR cigs developing around 12z
and continuing through 18z, with some marginal improvement
Thursday afternoon, but still primarily MVFR cig restrictions




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