Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 150030

Area Forecast Discussion
National Weather Service Cheyenne WY
530 PM MST Sat Jan 14 2017

Issued at 525 PM MST Sat Jan 14 2017

Updated forecast to added Dense Fog with visibilities lower than
one quarter mile at times west of the Laramie Range along
Interstate 80. Will also issue a Dense Fog Advisory after
coordination with the Riverton office as a significant portion of
Interstate 80 is impacted. Advisory will be good through mid
Sunday morning. Although visibilities have fluctuated at
times...the lower and more sheltered valleys have seen persistent
visibilities below one quarter of a mile. Believe areas west of
Elk Mountain near Rawlins will see this fog...but it may develop
later tonight. Updates will be sent shortly.


.SHORT TERM...(This evening through Sunday)
Issued at 154 PM MST Sat Jan 14 2017

A seasonal weekend in store for southeast WY and the western
Nebraska Panhandle as we keep watch on an area of low pressure
spinning across the Baja of California. Visible satellite imagery
early this afternoon shows most areas east of the Laramie Range
cloud-free, though clouds are beginning to increase from the south
as the initial band of moisture advects northward from upper-low.
This trend of increasing clouds south to north will continue
through Sunday. West of the Laramie Range, low clouds and patchy
fog linger early this afternoon as deep existing snow pack and
weak winds make valley inversions impossible to break. Case in
point is the 1 PM temperature difference of 19F between Cheyenne
and Laramie. Areas of fog will continue lifting into stratus
today, but will be quick settle back into lower elevations of
Carbon/Albany counties later tonight and Sunday morning.

Upper-low becomes positively tilted and ejects northeast into west
TX by late Sunday. Initial band of moisture may just be able to lift
far enough north by Sunday afternoon to bring small snow chances
just into the southern Nebraska Panhandle. However, confidence is
increasing that best snow chances will hold off even for this area
until after 00Z Monday. High temperatures will tick back a few
degrees across the entire CWA as cloud-cover thickens.

.LONG TERM...(Sunday night through Saturday)
Issued at 154 PM MST Sat Jan 14 2017

Still looking like a glancing blow for our area with the storm
system still projected to pass to our southeast Sunday night
through Monday. The models continue to track the upper low from
northwest Texas across eastern Kansas keeping higher impacts to
our southeast. The 12Z ECMWF remained a bit farther north and
west with snowfall, developing a brief band of snow from the Snowy
Range east across the Cheyenne area Sunday night. For this
forecast cycle we stayed close to the ensemble blends keeping a
chance of snow going for the Cheyenne area east across the
southern Nebraska Panhandle Sunday night into Monday morning then
tapering PoPs down. Highest snowfall amounts expected at this time
would be between 1 and 2 inches for the Sidney area with lesser
amounts west and north. Rest of the new work week looks to be dry
albeit breezy to windy at times along and west of Interstate 25
Tuesday through Thursday as the pressure gradient tightens in
response to lee side troughing east of the Laramie Range.


.AVIATION...(For the 00Z TAFS through Sunday afternoon)

Main impacts to aviation operations will be at KRWL and KLAR
terminals, where low clouds and fog linger. See no reason to remove
LIFR conditions from each terminal as KLAR is reporting Dense Fog
and a vis below one quarter mile this evening. Unless cloud cover
aloft develops with some sort of surface not see these
conditions improving any time kept IFR to LIFR conditions
in the TAF until mid-late Sunday morning. Otherwise...VFR conditions
will prevail elsewhere with just some increasing clouds tonight.


Issued at 154 PM MST Sat Jan 14 2017

Minimal fire weather concerns this weekend with the combination of
high humidity values and light winds.



WY...Dense Fog Advisory until 9 AM MST Sunday for WYZ109>111-113-115.



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