Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 152111

Area Forecast Discussion
National Weather Service Cheyenne WY
211 PM MST Sun Jan 15 2017

.SHORT TERM...(This evening through Monday)
Issued at 211 PM MST Sun Jan 15 2017

Over the next 24 hours, the primary forecast challenges center on
the continuation and likely re-development of fog along and west of
the Laramie Range tonight/early Monday and magnitude/p-type of area
of moisture lifting northeast from NE Colorado. First things first,
fog. Visibilities continue to lower below one quarter mile at times
along I-80 between Rawlins and Elk Mountain. Trends gradually point
to improving conditions this afternoon, likely a result of
increasing clouds associated with the upper-low passing to the
south. A Dense Fog Advisory remains in effect for central Carbon
County until 3 PM. Low clouds/fog will re-develop across the same
area later tonight, likely even affecting Cheyenne for a time.
Future shifts may very well need another Dense Fog Advisory tonight
should thickness/extent warrant.

The other concern for tonight and Monday morning has been trying to
peg down precip chances and p-type. Regional radars show band of
light-moderate precip lifting north across NE Colorado early this
afternoon. Models are in fairly good agreement that this precip band
will lift into at least the southern Panhandle by late afternoon and
this evening. The primary area of impact will be Kimball-Sidney
initially, before expanding into Laramie, Banner, and Morrill
counties tonight/Monday Morning. As for precip type, upstream
observations show a brief period of freezing rain and at both the
Imperial & Yuma Colorado observing sites. KSNY BUFKIT sounding
supports at least the potential of a short period of freezing rain
this evening. Previous shifts had this handled well and continued
for this evening as well. Although amounts will not be all that
much, it may be enough to produce some slick spots on area roadways.
Areas around KSNY will transition to light snow by late evening,
with perhaps 1-2 inches of accumulation by Monday morning. Areas
north and west of Sidney will likely see all snow, with perhaps up
to an inch of accumulation. In general have increased precip chances
during this time period.

Any lingering snow will wind down quickly on Monday, likely even
seeing some sunshine in most areas by afternoon. High temperatures
will be similar to today, reaching the 20s west and 30s east.

.LONG TERM...(Monday night through Sunday)
Issued at 211 PM MST Sun Jan 15 2017

Rapid clearing of snow to the southeast and east of our area and
clearing skies will continue into Monday night and continue
through midweek as the shortwave trough moves east onto the High
Plains and upper ridging moves in. Models continue to point to the
formation of a lee side trough by Tuesday which results in a
tightening of the pressure gradient for areas along and west of
I-25. Based on what we see in the models right now, we are not
expecting a widespread high wind event Tuesday through Thursday,
but it will be breezy for much of SE Wyoming midweek with the
usual windier spots along I-80 and I-25 (Arlington, Elk Mountain
and Bordeaux) could see periods near or at criteria on maximum
gusts. Next shortwave moves in late in the week bringing a chance
of snow in the Sierra Madre and Snowy Ranges with smaller chances
out east onto the plains going into the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1232 PM MST Sun Jan 15 2017

MVFR/IFR conditions persist at KRWL and KLAR this afternoon as
patchy fog/low stratus continues there. Suspect to see some
improvement but confidence remains low just how much and where.
Expect conditions to deteriorate at these sites later tonight as
light winds, solid snow-pack, and moisture increases. For
terminals east of the Laramie Range, conditions will progressively
deteriorate later this afternoon south to north. The two
exceptions will be at KAIA and KCDR, which should be far enough
north to escape impact. KSNY, KCYS, and KBFF will see lowering
CIGS and light precipitation develop by tonight. KSNY may even see
some brief FZRA through around 05z, before transitioning all to
snow. Any icing would be very light of less than .01. Snowfall
amounts of around 1 inch is expected nr KSNY by midday tomorrow.


Issued at 211 PM MST Sun Jan 15 2017

No fire weather concerns over the next several days with above
normal humidity values.


WY...Dense Fog Advisory until 3 PM MST this afternoon for WYZ109.



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