Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 160554
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1050 PM MST Sun Jan 15 2017

.UPDATE...
Issued at 804 PM MST Sun Jan 15 2017

Issued a Winter Weather Advisory for Freezing Rain and snow for
the southern Nebraska panhandle tonight...including Kimball and
Sidney. Getting reports of icy roadways in that area. It has been
difficult to gather observed freezing rain reports...but with
Sidney ASOS reporting unknown precip recently...this was likely
some freezing rain and snow mix. The band is now near Broadwater
in Morrill county...and stretches westward towards Pine Bluffs
Wyoming at this hour with additional bands pushing in from the
south. Will continue to keep a close eye on this through the
night with the potential of other zones further north and west
being added to the advisory.

&&

.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 06Z TAFS through Monday Evening)

Main aviation concern is freezing rains across the southern Nebraska
panhandle and some light snow pushing towards KBFF...KAIA...and KCYS
tonight. Expect MVFR CIGS and VIS over the next few hours. Believe
there will be a period of IFR as the more intense bands of precip
move northward across the area after midnight. Freezing rain should
change over to all snow after midnight near KSNY as colder air aloft
begins moving into the area. There will be icing concerns through at
least 08z tonight before the colder air moves into the area.
Otherwise...LIFR conditions and fog will persist around Rawlins
through midnight...but there are some indications that fog may
dissipate between midnight and 09z resulting in slowly improving
conditions. Do not expect fog to develop over KLAR tonight...so
removed from the TAF but kept an MVFR CIGS around 1500 to 2500 feet
AGL.

&&

.FIRE WEATHER...
Issued at 211 PM MST Sun Jan 15 2017

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

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...Dense Fog Advisory until 10 AM MST Monday for WYZ109.

NE...Winter Weather Advisory until noon MST Monday for NEZ054-055.

&&

$$

UPDATE...TJT
SHORT TERM...CAH
LONG TERM...JG
AVIATION...TJT
FIRE WEATHER...JG/CLH


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