Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 260541
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1041 PM MST Sat Feb 25 2017

.UPDATE...
Issued at 920 PM MST Sat Feb 25 2017

Winds have ramped up considerably at Arlington this evening as a
50 kt jetlet moves over the mountains, with gusts around 65 mph
observed at the sfc on the WYDOT sensors. Short-term model
guidance does suggest winds may stay elevated for a few more
hours, so felt it prudent to issue a High Wind Warning for that
area. Winds should diminish by sunrise, although gusts to around
50 mph still likely in this area, and elsewhere in the wind prone
areas, through the morning.

UPDATE Issued at 310 PM MST Sat Feb 25 2017

Getting wind gusts at Bordeaux in excess of 60 MPH this afternoon.
Went ahead with a short fused High Wind Warning up there for this
afternoon and early evening. Strong winds expected to continue
into the overnight hours. Extended the Blowing Snow Advisory until
12Z Sunday. May need to be extended longer based on forecast
gradients. But for now, will let the evening and night shift take
a look at the 00Z model guidance before extending further. Updates
have been sent.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 300 PM MST Sat Feb 25 2017

Winds and blowing snow are the primary forecast challenges for our
area. Another snow event looking likely for Monday.

Currently...Strong winds over the wind prone areas this afternoon.
Arlington had a gust to 57MPH with widespread 50MPH gusts along
the Summit and up by Bordeaux. Strong winds and recent fresh snow
has caused areas of blowing snow over the Summit and out by
Arlington this morning and afternoon. Impacts have been the
closure of westbound I-80 over the Summit and out by Arlington.
Latest high wind guidance showing the Craig to Casper 850/700mb
gradients remaining elevated through the afternoon. May need to
extend the blowing snow advisory through tonight, especially the
Summit and Arlington. Bordeaux not being impacted as much. Will
see what happens later on this afternoon before taking any further
action.

Looks like another windy day Sunday. Should be a little warmer and
any snow that was going to blow, should have done it today. So
held off on adding blowing snow into the forecast. Later shifts
may need to add though depending on later observations.

Next Pacific shortwave still on track for Monday/Monday night.
Both the GFS and ECMWF very alike on timing with the Snowy and
Sierra Madre Mountains seeing moderate to heavy accumulations.
Likely going to need winter headlines for these two zones. If
similar tomorrow, will go with a headline to highlight conditions.

.LONG TERM...(Tuesday through Saturday)
Issued at 300 PM MST Sat Feb 25 2017

Tuesday...Next shortwave trough aloft moves across southwest Wyoming
with enough low and mid level moisture advection to produce a chance
of snow over and near our Snowy and Sierra Madre Ranges. Dry
elsewhere. Colder day with more cloud cover and cooler air moving in
at low levels.

Wednesday...Winds look to strengthen on the first day of March as
flow aloft turns northwest and the low and mid level gradients
strengthen. Temperatures remaining cold based on projected 700 mb
temperatures and cloud cover. Enough moisture for a few orographic
snow showers over the Snowy and Sierra Madre Ranges, dry elsewhere.

Thursday...Slow warming trend starts as the heights aloft rise,
along with increases in 700 mb temperatures and thicknesses, though
surface high pressure building southward across the high plains will
limit warming potential.

Friday...Warming trend continues in earnest as the flow aloft backs
to straight zonal and a decent surface lee trough develops in
response. With limited low and mid level moisture and no lifting
mechanism, dry day expected.

Saturday...Warming trend continues as the flow aloft turns
southwest. Strong winds look likely, especially in our wind prone
locations considering strength of the low and mid level gradients.
Continued dry with lack of low and mid level moisture.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1041 PM MST Sat Feb 25 2017

VFR conditions are expected to continue through the period with
mainly some high clouds moving overhead from the northwest. Winds
will be gusty as times, especially late Sunday morning through the
afternoon where gusts of 20-30 kts will be common across the
area. Even stronger gusts are likely in the high country.

&&

.FIRE WEATHER...
Issued at 300 PM MST Sat Feb 25 2017

Fire weather concerns at a minimum with a large and widespread
snowpack. Strong winds in the wind prone areas today will
continue to create blowing and drifting snow through this evening.
A windy period ahead with strong winds in our normal wind prone
areas through much of the upcoming week. With cold temperatures
and existing snow pack though, fire weather concerns are not
expected.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 3 AM MST Sunday for WYZ110.

     Winter Weather Advisory until 5 AM MST Sunday for WYZ106-110-116-
     117.

NE...None.
&&

$$

UPDATE...RJM
SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RJM
FIRE WEATHER...GCC


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