Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 042339 AAA
AFDGJT

Area Forecast Discussion...UPDATED
National Weather Service Grand Junction CO
439 PM MST Sun Dec 4 2016

updated aviation discussion

.SHORT TERM...(Tonight through Monday night)
Issued at 404 PM MST Sun Dec 4 2016

A warmer night is in store for eastern Utah and western Colorado
with increasing mid and high level moisture bringing mostly cloudy
to cloudy conditions back into the area. Moisture deepens
sufficiently over the Park mountains by Monday morning that we
will start to squeeze out a few snow showers. This activity will
increase as westerly flow strengthens with a series of fast moving
waves rolling through. Expect snowfall to increase over the Park
Range Monday morning and then sag slowly south into the Flat Tops
by midday with a continued shift south into the Central Mountains
by evening. H7 flow bends from 26050kts to 34025kts between 9 am
and 3 pm Monday as the first wave passes.

The favorable shift in wind fields will aid in snowfall
production with temps tumbling from -6c at 12z Monday morning to
around -18c by midnight Monday night. We should see a period of
heavier snowfall as the colder air sags south although duration
will be rather short with this first onslaught of wind and snow.
Total accumulations for our mountains along and north of
Interstate 70 should range in the 2-6" range by late Monday night
with lighter amounts near Vail Pass. However, impacts from wind
driven snow will be felt, especially over the higher passes with
gust potential to 50 mph or better.

Snow will diminish after midnight Monday night as this first
series of ripples work through, but the flow is fast and more
energy rolls in by midday Tuesday. Stronger upper level wave and
associated sfc front roll in by afternoon with 125kt jet working
across Utah and into the Four Corners area. This will allow
snowfall to shift south into the central mountains with activity
picking up throughout the day on Tuesday. Banding along the
leading edge of arctic front sagging south into the region will
provide focus for locally heavier snowfall. Some question as to
exactly where this will set up, but fairly high confidence that
the Central Mountains will reach at least advisory criteria by
late Tuesday. As such, have upgraded the winter storm watches in
effect for the northern and central mountains to snow advisories
with subtle adjustments to timing to fit expected trends. Have
left the Grand Mesa and West Elks out for now, but will be areas
to watch for inclusion into the snow party.

Temperatures will be running right around normal for this time of
year through Monday with steady cooling rolling in Monday night
and Tuesday as some of the coldest air of the season tries to
spread south over our area.

.LONG TERM...(Tuesday night through Sunday)
Issued at 404 PM MST Sun Dec 4 2016

Upper level wave passes through Tuesday night with moisture
eroding from west to east. Still expect a few snow showers to
hang on through early Wednesday before brief period of drier
weather moves back in. Wednesday will also be the coldest day of
the week with sfc front dropping south across the entire
forecast.

Ridging to our west will keep northwest flow in place for the
remainder of the week. This will drive another round of Pacific
storms through the area with first in this series arriving as
early as Thursday afternoon. This will also be driving warmer
weather back into the area with a gradual increase in snow levels
expected through the end of the week. Expect a long duration event
over the Park and Gore mountains.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 438 PM MST Sun Dec 4 2016

VFR conditions will prevail thru the period. However ceilings are
expected to drop just below ILS breakpoints at KASE and KEGE by
midday Monday as moisture associated with upper level wave passing
to the north increases and brings chance of snow showers to their
vicinity as well. Otherwise, increasing winds aloft will present
the risk of LLWS at the higher TAF sites of KASE and KTEX
overnight and Monday morning.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory from 9 AM Monday to 6 AM MST Wednesday
     for COZ004-013.

     Winter Weather Advisory from 6 PM Monday to 6 AM MST Wednesday
     for COZ010.

UT...None.
&&

$$

SHORT TERM...JDC
LONG TERM...JDC
AVIATION...BEN



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