Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 192241

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
341 PM MST Mon Feb 19 2018

.SHORT TERM...(Tonight through Tuesday night)
Issued at 341 PM MST Mon Feb 19 2018

Another one of those exciting weather days across eastern Utah and
and western Colorado as a strong upper level system and its
associated cold front sweep across the region. Gusty southwest
winds will continue to plague the southern half of the forecast
areas through this evening, basically from Interstate 70 south to
the New Mexico state line. Had gusts clock in over 100 mph over
the higher peaks with 50 to 60 mph gusts elsewhere. Have adjusted
the wind highlights a bit for this evening, dropping them from the
I-70 corridor and shift them south into the southwest valleys
including Pagosa Springs and Durango. Latest LAV guidance
bringing peak gusts to near 50 mph for a few hours this evening.
Add in the bonus convective showers and potential remains high to
see these type of winds into the evening hours. Expect to winds to
diminish behind the strong cold front that is making the rare
push south during the daylight hours with the front likely
accelerating a bit as the sun sets.

Focus then shifts to the snow portion of this strong winter storm.
Latest HiRez models keeping these bands active through late
tonight as we see the upper level jet move in overhead with the
approaching H5 trough axis squeezing in behind later tonight. The
emphasis of our snowfall will also be shifting from the southwest
facing slopes to the west and northwest facing slopes overnight.
This places our central mountains in better position to pick up
heavier snowfall overnight and nudge numbers up closer to a foot
in the Aspen and Snowmass areas with amounts tapering off as we
work northeast toward Vail. Still solid advisory amounts which we
already have in place. Namnest is also showing some decent bands
aligning along the I-70 corridor and advisory were issued for
these areas earlier this afternoon for up to 6 inches of valley

The northern zones were enjoying some overrunning enhanced
snowfall as the warmer air aloft rode over the top of the
deepening cold pool north of the Bookcliffs. Earlier banding also
brought heavy snow into the Vernal and Flaming Gorge areas with
the band aligned roughly along the Green River. GOES-East picked
that up nicely in a few our our RGB curves. Expect the snow across
the north to become more stratiform as the evening progresses with
snow persisting through the early morning hours before drier
conditions push in from the north.

Pushing back to the south, the strong front will continue to drive
southward this evening, reaching our southernmost zones by
midnight or shortly thereafter. Widespread snow over the San Juans
will persist with southwest slopes losing out once the front
passes, which is good news for the northwest facing slopes.
Overall amounts should still approach a foot plus over most of the
San Juans with higher amounts up above the 12k mark. Looked at the
southern valleys fairly closely for potential winter highlight
level snowfall. Checked model soundings, meteograms and time-
heights across the southern valleys supports amounts in the 1-3
inch range with possibly a bit more along the mid-slopes. So will
stick with the wind products for now and have the evening shift
keep close tabs on these areas.

Temperatures will be down a good 10 to 15 degrees in most
locations on Tuesday with snow showers persisting through the day.
Winds will be lighter as we recover from this wind, rain and snow
event. One last piece, convective potential has fell off
significantly this afternoon and have removed the thunder from the
forecast overnight.

.LONG TERM...(Wednesday through Monday)
Issued at 341 PM MST Mon Feb 19 2018

The next Pacific system will be carving our a long wave trough
over the Western U.S. Wednesday and Thursday with flow shifting
back around to the southwest. Models dragging a bit of moisture
northward in the San Juans and southern Valleys Wednesday night
and Thursday. GFS and NAM generating light to moderate QPF that is
focused over the San Juans and near Pagosa Springs. Have not dove
into this system hard core yet with emphasis today on the current
system. The quick takeaway here is that we should see another
round of snow across the southern zones going into the day on

We are still not done by any means as the long wave trough to our
west is expected to lift out and across the Great Basin later
Thursday and Friday. Strong southwest flow out ahead of it will
keep moisture lifting northward and would expect to see more wind
as we often do moving into the Spring months. WAA showers will
have the potential to bring moderate snowfall to the mountains
with rain/snow showers over the valleys through Friday. Colder air
arrives Friday night and Saturday, which is the period where
snowfall amounts should tick up, especially across the central
mountains and northwest San Juans. Pattern is somewhat repetitive
right now, which is a good thing as we enjoy one of the snowier
February`s in recent memory.

Spring-like roller coaster anticipate with temps with below normal
readings to start off, warming back to more normal levels by
Friday, then dropping off again over the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1003 AM MST Mon Feb 19 2018

A passing cold front producing low clouds, variable precipitation,
gusty winds will all combine to create variable flight conditions.
The precipitation will be very showery which means VFR conditions
could quickly become LIFR as snow showers pass by or settle in.
Winds will be impacting not only landing and takeoff operations
but mountain turbulence should again be present. Expect widespread
terrain obscuration as well. Conditions not likely to improve
until later in the day on Tuesday as this storm winds down.


CO...Winter Weather Advisory until 8 AM MST Tuesday for COZ001>005-

     Winter Storm Warning until 8 AM MST Tuesday for COZ009-012-013-

     Wind Advisory until 5 PM MST this afternoon for COZ006-007-011-

UT...Winter Weather Advisory until 8 AM MST Tuesday for UTZ025-028.

     Winter Storm Warning until 8 AM MST Tuesday for UTZ023-024.

     Wind Advisory until 5 PM MST this afternoon for UTZ022-027>029.



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