Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 022217
AFDGJT

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

.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 00Z TAFS through 00Z Saturday evening)
Issued at 316 PM MST Fri Dec 2 2016

Moist southerly flow into the southern and central Colorado
mountains is bringing some light snow and lower cigs to the
region. MVFR to IFR conditions with plenty of high terrain
obscured by clouds will persist into the late evening hours.
KTEX...KASE are the most likely terminals to be impacted by the
weather through 03/06Z. 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.
&&

$$

SHORT TERM...15
LONG TERM...15
AVIATION...TGJT



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