Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 200940

Area Forecast Discussion
National Weather Service Cheyenne WY
240 AM MST Fri Jan 20 2017

.SHORT TERM...(Today through Sunday)
Issued at 240 AM MST Fri Jan 20 2017

Fairly quiet weather expected across the CWA through this weekend.
An upper trough will pass across the region today with the bulk of
its energy passing south across Colorado. It should produce some
higher mtn snows with more isolated rain/snow showers elsewhere
across the CWA today and over the Panhandle this evening. Mainly
dry Saturday and Saturday night as the upper flow becomes
northwesterly on the top side of an upper ridge that will move
across the desert southwest. Orographics may help to produce a
few snow showers over the higher mtns late Saturday into Saturday
night then mainly dry Sunday as the ridge axis moves by the area.
Temperatures cool but seasonable across the CWA through the

.LONG TERM...(Sunday night through Thursday)
Issued at 240 AM MST Fri Jan 20 2017

Models continue to show some agreement in the extended with the
development of the low pressure system over the plains Monday night-
Tuesday. Still plenty of uncertainty tho in the details, and models
are weaker and more progressive with the system than previous runs.
Went with a persistence forecast during this timeframe, maintaining
a good chance for snow over the mountains starting Sunday night as
the 150+kt jet moves overhead, then steadily spreading east into the
plains Monday night through Tuesday as the low strengthens. With the
progressive nature of the system, should be a relatively quick shot
of widespread light to moderate snow. Sfc winds will shift to the
north and strengthen as leeside cyclogenesis occurs in eastern
CO/western KS early Tuesday morning, so could be dealing with
impacts due to both snow and blowing snow. Temperatures will drop in
the wake of this system as northerly flow aloft advects a cold
Canadian airmass into the western CONUS. Slightly below normal
readings are expected Tuesday night through Thursday, however
wouldn`t be surprised if temps go even colder with a fresh snow pack
in place. A few midlevel disturbances in this flow pattern could
maintain light snow showers here and there across the forecast area.
However, models differ quite a bit with details in the 500mb
vorticity, so kept PoPs low overall and just highlighted the
mountains for now.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1030 PM MST Thu Jan 19 2017

Clouds will increase and lower from west to east overnight and
Friday. VFR cigs will prevail east of the Laramie Range, with
periods of MVFR to IFR cigs/vis to the west as snow develops.
Airfields affected will be RWL and SAA. Light snow spreads east
to LAR late tonight with a period of MVFR cig/vis between 14Z and
18Z Friday. West to northwest winds 10 to 15 kt will prevail, with
gusts to around 20 kt at CYS Friday.


Issued at 240 AM MST Fri Jan 20 2017

Minimal concerns seen through the weekend with non-critical fuels
and weather conditions remaining on the cool side. Some light pcpn
expected over many areas today into this evening then mainly dry
over the weekend.




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