Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 131302

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
602 AM MST Tue Feb 13 2018

Issued at 600 AM MST Tue Feb 13 2018

With a small band having set up from Meeker down to just west of
Fruita, and snow still occurring across several portions of the
CWA, don`t feel comfortable dropping any highlights. Pushed them
out through 9AM to get some ground truth on what`s going on.
Anticipate once the sun comes up, they`ll can be pulled down.
Until then, better safe than sorry.


.SHORT TERM...(Today through Wednesday)
Issued at 334 AM MST Tue Feb 13 2018

Snow continues for a few areas this morning though intensity has
decreased as expected. Latest radar imagery shows another area of
precip moving in from Moab up into the western sections of the
Grand Valley and up into Meeker. Some lighter snow also looks to
be occurring over Eagle and into Gunnison. The heaviest snow
continues in Pagosa Springs and up to Wolf Creek Pass. All
warnings and advisories are due to expire at 6AM and looks like
most will be allowed to expire. Will probably keep southern San
Juans and Pagosa Springs going through 9AM to account for
continued snowfall there.

A concern this morning will be widespread fog with Montrose and
Delta already seeing 1/4 mile visibilities due to dense fog. Dense
fog advisories have been issued for those areas and will keep an
eye on the Grand Valley and along the I-70 corridor for more
advisories, if needed.

Some light snow and rain will continue this morning across the
forecast area but weaken as the day progresses. The area of low
pressure to our west is expected to continue to move westward
which will cause upper level support to wane and thus,
precipitation will slacken. From about noon onwards, precipitation
will become more showery and favor the higher elevations.

Wednesday, the low will now be off the California coast and start
filling (meaning weaken). While this occurs, another trough will
start dropping down from the northwest. Models in fairly good
agreement that snow will begin for the mountains Wednesday evening
and increase overnight into Thursday. Amounts look to be in the
advisory range (5 to 12 inches) with a few spots probably seeing
higher amounts. More precipitation the better.

.LONG TERM...(Wednesday night through Monday)
Issued at 334 AM MST Tue Feb 13 2018

The upper level low off the southwest coast will be filling and
phasing in with an incoming Pacific wave diving south out the
Gulf of Alaska. The incoming Pacific system will tap available
sub-tropical moisture to our southwest and swing in back up into
our neck of the woods beginning Wednesday night as nose of 130 kt
jet moves in overhead. Increasing jet dynamics associated with
speed max, shot of cooler air aloft and mid/low level flow
bending to a more westerly component will be enough to get showers
rolling in earnest Wednesday night. This event will persist
through Thursday with moderate to potentially heavy snowfall
amounts again expected for most of the high country. Valleys
should also see a decent shot of accumulating snows should
everything hold together.

Based on the more westerly component, would expect the central
mountains to do a bit better with Telluride also getting into the
game. Still some time, but current thinking is that we will end
up with another solid advisory event for the mountains with
potential highlights into the valleys. Drier conditions spread
back over for Friday and Saturday with the models starting to
diverge once again as we move into early next week. This has
sparked another round of low confidence late in this extended
period. However, both the ECMWF and GFS are suggesting another
round of rain/snow late in the weekend and into Monday.

Temperatures will remain seasonal through the period, possibly a
few degrees above normal throughout this extended period.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 334 AM MST Tue Feb 13 2018

We will be in the muck for most TAF sites all morning. MVFR/IFR
will be common in fog, low clouds, and precipitation. KMTJ has
dropped to 1/4 mile in fog while KGJT and KEGE have dropped to 3
miles. KTEX and KGUC are seeing some light snow dropping
visibilities to 1 mile and 2 1/2 miles, respectively. Snow should
end shortly though fog will persist through 16 to 17Z. Once fog
clears, broken to overcast skies are expected but `should` lift
into the VFR category with ceilings between 5K to 10K feet. This
should occur after 18Z or so.


CO...Winter Weather Advisory until 9 AM MST this morning for

     Dense Fog Advisory until 9 AM MST this morning for COZ011.

     Winter Storm Warning until 9 AM MST this morning for COZ019.



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