Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 030543
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1043 PM MST Fri Dec 2 2016

.UPDATE...
Issued at 805 PM MST Fri Dec 2 2016

There has been quite a bit of light snow reported mainly east of
a line from Hayden to Grand Junction to Cortez this evening in the
deformation and weak upglide area ahead of the northern stream
upper level trough pushing into NW colorado at this time. Short
range models keep a decent sized area of saturated crystal growth
zone over western Colorado through 11 pm...but current IR
satellite imagery is showing a general decrease in clouds. Expect
higher elevations...especiall south of Interstate 70 will continue
to see light snowfall through midnight...then decreasing coverage
overnight. Flurries possible from time to time over the adjacent
valleys. Overnight accumulations should be less than one inch.
Have made updates to forecast to hold on to higher snow
probabilities through midnight.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 316 PM MST Fri Dec 2 2016

The 12z H500 hand analysis is showing a rather anomalous pattern
in place with higher than normal heights extending from the
EPAC into the high latitudes of E.NOAM. Lower than average
heights are set up across the southwest CONUS with split trough in
place with one circulation over the the northern high plains and a
more distinct low spinning over the Baja/CA/AZ border. A rather
strong upper jet is rounding the southern base of the trough which
is aiding southerly flow from the eastern Gulf of Mexico up the
lee of the Rockies into southern Colorado. The 295K-300K surfaces
are showing this moist upglide well with the result being light
snowfall over much of our eastern mountains south of I-70. This
pattern will gradually shift eastward overnight as a stronger
piece of the Pacific jet noses in upstream. The drier downglide
behind the trough will allow showers to gradually end during the
early morning hours. The drier air and mainly clear skies will
lead to a rather cold morning across the region by Saturday.
Plenty of sunshine will then be around to begin the weekend but
afraid the valley inversions will have a good start and highs on
Saturday may struggle a bit. A bit of moisture and weak upglide
will cross the northern mountains late Saturday afternoon but
can`t see this being much more than flurries to very light
accumulations. Temperatures Sunday morning will remain colder than
normal.

.LONG TERM...(Sunday through Friday)
Issued at 316 PM MST Fri Dec 2 2016

All eyes will be looking upward to the northern high latitudes for
the developing cold weather pattern next week. At the moment this
is a well defined trough extending from the North Pole into the
Gulf of Alaska. Basically this low pressure area will shift into
the Canadian prairies and as the Polar jet buckles on
Monday...arctic cold air will have an open door southward into the
lower 48. Pacific moisture and lift from the this arctic front
arrive to our northern border by mid morning on Monday. The best
focus for precipitation will be over our northern mountains and
valleys near this front on Monday. Models begin to diverge on
Tuesday with the arrival of a backside energy re-enforcing the
large low circulation residing over central NOAM. At one point
models developed this secondary system into a fairly good weather
maker for our CWA...however that trend as continually lessened
over the past several days. Even the stubborn ECMWF is slowly
becoming more progressive. There will be snow around our northern
and central CWA on Tuesday but confidence is not high on just how
far south we can dig the energy. The cold however will filter into
the region and we can expect highs some 15 to 25 degrees colder
than normal to arrive by mid-week with even some single digit low
temperatures showing up in the lower valleys through the end of
next week. This could still turn into a major storm but for now
the probability of that happening is not very high. Stay tuned.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1043 PM MST Fri Dec 2 2016

Moist southerly flow into the southern and central Colorado
mountains in advance of upper level trough will continue to bringsome
light snow and lower cigs to those areas. MVFR to IFR conditions
with plenty of high terrain obscured by clouds will persist thru
09-10Z. KTEX...KASE are the most likely terminals to be impacted
by the weather through 03/09Z. The weather will be pushed
eastward by sunrise and improved conditions can be expected on
Saturday. However some low cloudiness may persist in the valleys
through mid morning.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

UPDATE...BEN
SHORT TERM...15
LONG TERM...15
AVIATION...BEN/JAM


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