Area Forecast Discussion
Issued by NWS Grand Junction, CO

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810
FXUS65 KGJT 170544
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1044 PM MST Mon Jan 16 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 157 PM MST Mon Jan 16 2017

Light snow continues in the San Juan mountains this afternoon.
Easterly flow has continued to transport moisture back west over
the divide in southern Colorado the low pressure system we have
been dealing with over the past few days heads east through the
central plains. The main forecast challenges this evening will be
timing the end of this precipitation, and whether or not
temperatures will fall enough to allow the snow to stick in
locations such as Cortez and Durango. Dynamic support for snowfall
really wanes after midnight tonight, with 700mb flow becoming
light and variable around this time. While model guidance still
suggests low level moisture over the southern half of Colorado,
little in the way of lift will remain after midnight and it is in
that time that snow is expected to finally come to an end.
Temperatures this evening will drop back into the mid-20s in the
southern valleys, however meaningful precipitation will be over
by this time. We are not expecting any accumulations anywhere but
in the higher terrain of the San Juans, where a final 1 to 3
inches will fall before the end of the event Tuesday morning.

Clouds will linger from Interstate 70 southward on Tuesday, with
partly to mostly sunny skies in the north. Overnight lows will
reflect this trend with the typically colder northern valleys
dropping to near 0, and the southern half of the forecast domain
generally in the 20s. The weak upper-level low forming over the
southwest, mentioned in previous discussions, has remained on
guidance today so we can not entirely rule out a fresh snow shower
in the San Juans Tuesday afternoon. Weak west to northwesterly
flow will push this system away by Tuesday night into Wednesday
morning with another chilly but seasonable night expected.

.LONG TERM...(Wednesday through Monday)
Issued at 157 PM MST Mon Jan 16 2017

500mb heights will finally begin to rise in earnest on Wednesday
afternoon. We are expecting a dry day across the entire region
with temperatures running a few degrees above average. On
Thursday, the axis of the 500mb ridge will pass over eastern Utah
and Western Colorado by mid-afternoon. High clouds ahead of the
next series of storm systems (yes, there will be more than one)
will overspread the region during the afternoon hours.
Persistence-plus will be a good rule for highs on Thursday as
most locations will add a degree or two on Wednesday`s temps.

The first in a series of three weak shortwaves will spread
precipitation into eastern Utah by later Thursday afternoon.
Guidance has been flip-flopping throughout the weekend on the
timing of the valley rain/mountain snow. Consensus in 12z guidance
suggests the eastern Uintas could see precip as early as 2pm
Thursday, with the rest of the higher terrain along the UT/CO
border later in the afternoon. With plenty of dry air in place and
relatively weak forcing, it will be tough for valley locations to
see much in the way of significant precipitation from this event.
The best chance for precipitation area-wide will be around
noontime Friday, with a light snow event in the mountains and
showers in the valleys. After a brief break in the action Friday
night, the next shortwave moves in for Saturday afternoon. This
system appears slightly more robust than the first, and will
usher in slightly colder air with 700mb temperatures around -8 to
-10 across the region Saturday. The maximum in precipitation with
this event will be from Saturday afternoon into early Saturday
evening.

Northwesterly flow with upslope snow showers will continue through
Sunday after this event in the mountains, before weak ridging
moves in and drys things out for Sunday evening into Monday. A
third storm system has come into focus on both the GFS and ECMWF
late in the Day 7 (Monday evening) timeframe. It certainly looks
like we will be back in an active pattern once again - much to the
delight of mountain snow lovers across the central Rockies.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1002 PM MST Mon Jan 16 2017

Light snow showers will persist over the San Juans through at
least 12Z, before coverage becomes more isolated through 18z.
These periods of showers will result in MVFR and IFR cigs/vis
impacting KTEX and KDRO. Expect low stratus and patchy fog to
develop overnight especially over KVEL and KASE. Elsewhere,
generally VFR conditions will prevail as drier air moves in under
a building ridge of high pressure for Tuesday.

&&

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

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...MPM



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