Area Forecast Discussion
Issued by NWS Grand Junction, CO

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175
FXUS65 KGJT 221101
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
401 AM MST Thu Feb 22 2018

.SHORT TERM...(Today through Friday)
Issued at 401 AM MST Thu Feb 22 2018

As models had predicted, a low pressure trough was moving eastward
across western Utah/Arizona early this morning. Ahead of the
trough a broad swath of snow had developed which extended from
southwest Colorado to KHDN in the north, primarily east of a K4V0
to KCNY to KCEZ line. Snotel sites in the southeastern San Juan
Mountains indicated the best accumulations, with estimated
accumulations of 3 to 6 inches or more.

The base of the trough will rotate through with a negative tilt
this morning. Jet divergence, mid-level lift and orographics
continued to favor the southwest San Juan Mountains according to
models. Understandably, models center the best accumulations over
the Pagosa Springs and the San Juan Mountains to the north
through noon. Snow will impact the central, and to a lesser
extend, northern Colorado Mountains and adjacent valleys as well,
but accumulations likely to remain below advisory criteria. During
the afternoon, dynamic forcing becomes less of a factor and
snowfall will become more showery in nature as the 5H cold pool
approaches yielding steep lapse rates.

Poorly organized snow shower activity is expected to continue
tonight and Friday as a second trough makes its way across the
Great Basin. As the system draws closer snow should begin to fill
in, becoming more widespread as the day progresses. This activity
may require additional highlights for Friday and beyond, but
confidence with respect impacts and timing not quite there yet.

Temperatures will remain cooler than normal today as clouds and
snow limit insolation across the region. Little change in readings
were indicated for tonight or Friday.

.LONG TERM...(Friday night through Wednesday)
Issued at 401 AM MST Thu Feb 22 2018

By Friday night, the base of the upper level trough will be over
eastern Utah while the surface reflection of said trough will be
over western Colorado. The heaviest precipitation will be riding
along and just ahead of the cold front with snowfall expected from
the northern mountains southwestward through the Grand Mesa and
down to the La Sal Mountains. Saturday morning, the front will
move moved to the Front Range with only a few orographic showers
to contend with over the Continental Divide. When all is said and
done, total snowfall amounts look to be in the advisory level
range (generally 6 to 12 inches for the mountains) for the higher
elevations of Colorado. The big question, as it has been most of
this season, will be if and where the heavier bands set up. Time
will tell and we`ll be monitoring as usual.

Saturday will bring `a bit` of a break but not much of one as
another piece of the polar front jet brings the next system from
the northwest. A few snowshowers will fall over the northern
mountains with more widespread snow beginning after midnight.
Models really favoring the mountains along the Continental Divide
for snowfall with most valleys staying mostly dry except those
close to mountain bases. This system looks to bring a quick shot
of snowfall with amounts hovering around 6 inches. This will
likely change as we get closer to the event but all in all,
amounts look to be on the lower side.

Monday and Tuesday will be quiet with variable cloudiness.
Temperatures will start to warm up thanks to southwesterly flow
advecting in warmer air. Wednesday onward, another system will be
on our doorstep but not much agreement between the GFS and EC. The
GFS brings a closed low down to the desert southwest and shifts it
eastward bringing us some light, isolated precipitation. The EC
brings a closed low across the Four Corners while also bringing
plenty of precip. With these model discrepancies, expect some
changes over the coming days. Can say this, let`s hope the EC
wins!

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1035 PM MST Wed Feb 21 2018

Snow has started across the southern valleys with low ceilings and
visibilities being reported there, except KDRO though expect
they`ll start soon. A few other spots are also reporting snow at
this hour to include KGJT. TAF forecasts for the next 24 hours
will be tricky as ceilings and visibilities drop to MVFR/IFR and
then back to VFR through the day. This trend will continue through
the day. Southern TAFs will be most affected though central TAFs
will likely see this from time to time as well. ILS breakpoints
will be reached for central and southern TAFs. Expect mountains to
be obscured for most of the day due to snow and lower ceilings.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until 6 PM MST this evening for COZ019-
     022.

     Winter Storm Warning until 6 PM MST this evening for COZ023.

UT...None.

&&

$$

SHORT TERM...NL
LONG TERM...TGR
AVIATION...TGR



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