Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 252132

Area Forecast Discussion
National Weather Service Cheyenne WY
232 PM MST Sun Feb 25 2018

.SHORT TERM...(This evening through Monday)
Issued at 205 PM MST Sun Feb 25 2018

Strongest winds are moving across the southern Wyoming mountains
this afternoon. In general, wind gusts are in the 40-60 mph range,
but we have seen some wave enhancement with gusts as high as 76
mph along I-80 in the Elk Mountain/Arlington area. There was
substantial blowing snow for a few hours this morning, but the
loose snow appears to be depleting and the low visibilities are
much more limited now.

This morning`s models are seeing more of the jet streak moving
onshore in the northwest, and the NAM in particular is holding the
flow over Wyoming more westerly and stronger into Monday morning
than previous runs. The GFS has this trend too, but not as much.
The NAM solution has WSW winds at 45-50 knots at 9000 ft MSL at
12z Monday. This would continue the high wind threat into Monday
morning. While the strong winds from this afternoon should
diminish by evening, there`s a good chance of having occasional
gusts around 60 mph in the windier spots until this next speed max
passes in the morning. We`ve decided to continue the warning for
most areas until 10 am, but will drop the Bordeaux area as it
looks even more marginal there at that lower elevation. Warmer
temperatures in the forecast for Monday look good.

.LONG TERM...(Monday night through Sunday)
Issued at 205 PM MST Sun Feb 25 2018

Lots of little things happening around us this week, but overall
it will be a mild and mainly dry period. A weak shortwave will
bring a front down across the plains Monday night, bringing a
little cooling. Just a chance of a little light snow in the high
mountains as this passes. Another wave will develop well south of
us on Wednesday, but again this will bring some cooling and a
chance of light mountain snow.

There is still much disagreement about the details of the
developing large scale trough over the northwest this weekend and
the shortwaves moving through it. There is agreement on warm and
initially dry southwest flow ahead of the trough, which should
bring quite mild temperatures for Thursday and Friday. The
operational GFS and about a quarter of its ensemble members have
a vigorous shortwave in the southwest flow late Friday, but it`s
working on a dry airmass. The EC and most of the GFS ensembles
have this wave later, and mostly weaker. If this shortwave is
strong, it would bring some cooling and more westerly flow for
more wind starting Friday or Friday night. The other solutions
would delay this change until Saturday, or in some runs, until a
stronger wave pushes the main trough axis eastward on Sunday. We
will eventually get cooler and windier with a chance of showers,
but for the plains at least this will probably wait until Sunday.
It`s also worth noting that if the trend toward a stronger,
further south jet continues, we may miss out on the best lift and
moisture from whatever does go by this weekend into early next
week. There is plenty of flow to work with, but the odds of
getting a stronger system to develop in the right place for
widespread precipitation don`t look that great at this point.


.AVIATION...(For the 18Z TAFS through 18Z Monday morning)
Issued at 1020 AM MST Sun Feb 25 2018

Strong westerly winds surface and aloft, as well as mountain wave
turbulence, will be the primary hazards for aviation operations
today across southeast WY. There are indications that the strong
winds may persist through Monday morning along and west of the
Laramie Range. MVFR CIG/IFR VIS in blowing snow will continue at
KRWL through at least 22Z before winds gradually subside there. It
will breezy at most NE Panhandle terminals this afternoon before
winds diminish after sunset. High clouds will increase from west to
east from this evening through Monday morning.


Issued at 205 PM MST Sun Feb 25 2018

Strong winds will diminish this evening, and even more so by
Monday afternoon. Humidities will remain above 30%. A mild period
with no strong winds is expected through at least Thursday.


WY...High Wind Warning until 10 AM MST Monday for WYZ110-116-117.

     Winter Weather Advisory until 8 PM MST this evening for WYZ110.

     High Wind Warning until 8 PM MST this evening for WYZ106.



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