Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 211710
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1010 AM MST Sun Jan 21 2018

.UPDATE...
Issued at 1010 AM MST Sun Jan 21 2018

Current satellite, radar and observations indicate snow has ended
or is ending across most valley locations of eastern Utah and
western Colorado...as well as the mountains of eastern Utah.
Therefore advisories and the Winter Storm Warning have been
allowed to expire or cancelled a few hours early for these areas.
Have kept advisories out for Douglas Pass and the Uncompahgre
Plateau with blowing snow the main threat keeping visibility down
for now, though not a lot of additional snow is expected. Cerro
and Blue Mesa Summits may accumulate light additional snow
amounts, but will mainly be socked in with fog for much of the
day. Advisories remain out for the mountains of Colorado, with our
eyes on the Gorge in the northern San Juans as a possible place
for snow enhancement this evening. Stay tuned...

UPDATE Issued at 559 AM MST Sun Jan 21 2018

Snow looks to have ended for the Vernal area so let the advisory
expire. Still snowing in the eastern Uintas though so extended the
warning through noon. Wouldn`t be surprised if it comes down early
though as models only show a few more hours of very light
snowfall.  Busy night!

UPDATE Issued at 504 AM MST Sun Jan 21
2018

The front is now moving through the Cortez area and from the looks
of webcams, bringing a nice burst of snow. CO-160 looks completely
snow covered which will certainly bring some travel impacts to the
region. Issued an advisory through noon for a quick 1 to 3 inches.
Unfortunately, radar not showing much for that region but think
it a safe bet that it`s snowing heavily along the Utah/Colorado
border for southwest Colorado so also included zone 20 in the
advisory. Also, if the front keeps moving east, don`t see any
reason it won`t bring some heavier snow to the Durango area,
especially for the higher terrain out west so included them too.

Looks a bit odd not including Montrose but looks like downslope is
keeping snow to a minimum in that region. Of course, will add if
the snow moves in there too.

UPDATE Issued at 400 AM MST Sun Jan 21 2018

Snow continues in the Grand Valley and while most roads are wet,
roads outside of town, according to Sheriff`s Office, are starting
to get slick with some snow accumulation. Latest guidance
continues to show minor snowfall over the next few hours so issued
advisory for 1 to 3 inches of snow. Advisory goes through noon
but expect it will be pulled down sooner as sun comes up and
snowfall ends.

&&

.SHORT TERM...(Today through Monday)
Issued at 338 AM MST Sun Jan 21 2018

A busy night as snow continues to fall across much of the forecast
area. The cold front is slowly moving across Colorado at this hour
and is and has been the focus of precipitation for much of the
night. Currently, the front is located from about Meeker southwest
to Grand Junction down to Gateway and then Blanding. Upper level
support is running generally south to north or parallel to the
front as opposed to more perpendicular which is causing the slow
moving lateral movement. Have been toying all night with issuing
an advisory for the Grand Valley as it has been snowing much of
the morning. Webcams do show some minor accumulation on roads but
really nothing too excessive so have held off. Will be interesting
to see what daylight brings. Another concerns is that the
NAMNEST, which is doing very well with this storm, keeps snowfall
in the Grand Valley for the next several hours. Radar does show
the edge of more moderate precip to be just west of Fruita so will
keep an eye on things and issue any highlights as needed. Other
concerns this evening were the Pagosa Springs and Blanding area.
Webcams for both places show some moderate to heavy snowfall and
again, the NAMNEST shows it continuing through the morning hours.
Did issue advisory for those areas through the afternoon for a
quick 3 to 5 inches but expect they`ll be able to be taken down
early once the front pushes completely through. As far as snowfall
is concerned, the winner so far looks to be the eastern Uintas
where 16 inches of new snow has fallen while we just received a
report of 8 inches in the Silverton area. About time considering
how dry this winter has been.

For the rest of today, temperatures will not get much higher once
the sun comes up as cold air advection really kicks in behind the
cold front. This cold air will also kick off some instability
showers (cold air over warm air) and may bring some light to
moderate snowfall to the mountains. For that reason, many
highlights will stay in effect except for eastern Utah and the
northern valleys which should come down a little later this
morning.

Monday, weak high pressure builds but some high clouds will come
with it. Most of the CWA will stay dry except for the northern
mountains. A weak shortwave will drop down from Idaho and should
bring some light snowshowers to the Park and Gore Ranges under
favorable northwest flow starting Monday evening and beyond. Some
accumulation is expected. Temperatures will be seasonal for this
time of year.

.LONG TERM...(Monday night through Saturday)
Issued at 338 AM MST Sun Jan 21 2018

A weak shortwave embedded in the northwesterly flow will drop
into northwest Colorado Monday night and produce a quick round of
orographic snow showers along the Continental Divide through
Tuesday morning. High pressure will rebuild over eastern Utah and
western Colorado for Tuesday afternoon and Wednesday and allow
skies to clear and temperatures to moderate. Meanwhile, the next
broad upper level trough will deepen off the coast of the Pacific
Northwest.

This trough will begin to move onshore Wednesday evening and
result in a transition to southwesterly flow over our forecast
area. A 90 to 100kt jet will be ushering this system into the
Great Basin Thursday night and Friday. While extended models
differ in terms of timing with this system, precipitation should
begin to spill into the region Thursday night and Friday morning
with the progression of a cold front. Some decent moisture and
cold air are associated with this trough at this time but have no
doubt there will be changes made in the coming model runs.
Northwesterly flow will set up in the wake of this system on
Saturday and will more than likely keep some orographic showers
going over the northern Colorado mountains. With the passage of
this trough and the associated cold front, temperatures will drop
back to seasonal levels.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 338 AM MST Sun Jan 21 2018

TAF sites will remain MVFR/IFR for much of the morning with
conditions improving from west to east following the cold front.
While conditions remain VFR for KASE and KEGE conditions should
start deteriorating from about 16Z onwards as snow moves in
bringing low ceilings and visibilities. Once the front moves
through, instability showers will kick-in causing more MVFR/IFR
conditions for a few TAF sites. Generally, the instability showers
will affect the mountain TAF sites. Widespread VFR will move back
in from between 21Z - 00Z.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 2 PM MST this afternoon for COZ003-
     009-012-017>019.

     Winter Weather Advisory until 9 PM MST this evening for COZ004-
     010-013.

UT...None.
&&

$$

UPDATE...JAM
SHORT TERM...TGR
LONG TERM...MMS
AVIATION...TGR


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