Area Forecast Discussion
Issued by NWS Cheyenne, WY

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884
FXUS65 KCYS 041028
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
328 AM MST Sun Dec 4 2016

.UPDATE...
Issued at 300 AM MST Sun Dec 4 2016

Was on the fence for a Winter Storm Watch for the Snowy and
Sierra Madre Ranges. After coordination with the Grand Junction
office though, decided to go ahead with the watch. Going to be
brutal weather up there with a good amount of snow, strong winds
and very dangerous wind chill temperatures. Snowmobilers and other
outdoor recreationists could easily get disoriented or lost in
these dangerous winter conditions. Updates have been sent.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 300 AM MST Sun Dec 4 2016

Very strong winds are the forecast challenge this morning with
snow/possible blizzard conditions following suite.

Currently...CWFA pretty much cloud free this morning. Strong
pressure gradient over the western and central portions of
Wyoming. Sea level pressure difference between Craig and Casper
stands at roughly 10mbs. Winds at Bordeaux and Arlington have been
on the increase this morning with gusts in the mid 40s being
reported at the WYDOT sites in those zones. Off to the northwest
in Washington and Idaho, widespread snow being reported on area
METARs with a low pressure system moving towards Wyoming.

For today, local high wind model guidance showing a rapid uptick
in 850/700mb Craig to Casper height gradients. Both the GFS and
NAM guidance has both above 60mtrs by 15Z this morning, peaking
out above 70mtrs after 00Z today. GFS 700mb winds over 60kts by
this evening across Albany and Carbon Counties as well as the
South Laramie Range. As a result, went ahead and upgraded the
watches we had out for Bordeaux and South Laramie Range to
warnings. Day shift will need to watch to possibly expand these
warnings to lower areas as the day goes on. MOS guidance though is
not showing strong winds at Cheyenne and Laramie, so held off on
any watches for these area. Would not be surprised though if we
get a few 60MPH gusts around these locations before the day is
over.

Front on track to move into Carbon County early Monday morning
around 12Z and through the southeast portions of our CWFA by 21Z
Monday afternoon. There will be some moderate snow areas with the
front out in Carbon County during the day Monday with downsloping
winds here east of the Laramie Range. Still seeing fairly strong
700mb winds Monday on the GFS behind the front across carbon and
Albany Counties. Winds 35-45kts with this snow could produce
blizzard to near blizzard conditions out by Arlington during the
day Monday. Decided to go with a Blizzard Watch for the Arlington
zone Monday with 1-3 inches of snow and these strong winds. As for
the mountains, am certain we will need some type of winter
headline for the Snowy and Sierra Madre Ranges. Right now, not
getting the snow amounts for warnings. Going to be pretty
miserable out there though with the strong winds and anywhere from
8-10 inches of snow. Will let the dayshift decide on winter
headlines out there this morning.

Front looks to wave back north late Tuesday near Laramie. Still a
couple days away, but winter headlines may be needed for the I-80
Corridor from Sidney to Laramie Tuesday night into Wednesday. Not
to mention wind chill headlines that are almost certain.

.LONG TERM...(Tuesday night through Saturday)
Issued at 300 AM MST Sun Dec 4 2016

Tuesday night/Wednesday...Shortwave moves from northwest Colorado to
southeast Colorado with a band of associated snow across northern
Colorado extending into southeast Wyoming. Have continued painting
snow Tuesday night mainly over far southeast Wyoming and the
southern Nebraska panhandle. Snow will end after daybreak Wednesday
as the area of lift and moisture moves southeast of our counties.
Continued bitterly cold on Wednesday with 700 mb temperatures only
around -20 degrees Celsius, yielding high temperatures in the single
digits and teens.

Thursday...Quite slow warming trend develops with northwest flow
aloft and a slowly moderating airmass.

Friday...As the flow aloft backs to west, the bitterly cold air will
shift to the east of our counties with high temperatures finally
climbing above freezing. Orographic snows will increase in coverage
and intensity across the Snowy and Sierra Madre ranges in advance of
the next shortwave.

Saturday...Progged shortwave moves across our counties early in the
day producing a chance of snow with lessening chances in the
afternoon in the wake of the shortwave. High temperatures at or
above freezing at most locations.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1146 PM MST Sat Dec 3 2016

VFR prevails. Gusts from 28 to 35 knots across Wyoming sites,
mainly before 00Z. Gusts of 20 to 22 knots at Scottsbluff and
Sidney after 18Z, lesser winds at Chadron and Alliance.


&&

.FIRE WEATHER...
Issued at 143 AM MST Sun Dec 4 2016

No fire weather concerns through next week as a very cold arctic
airmass settles over the area. Strong winds expected today,
especially in the wind prone areas of southeast Wyoming where
winds could gust as high as 70 MPH near Bordeaux and Arlington.
These strong winds are caused by an approaching low pressure
system in the Pacific northwest. Accumulating snow is possible
Tuesday and into Wednesday next week.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from Monday morning through Tuesday afternoon
     for WYZ112-114.

     High Wind Warning from 8 AM this morning to 8 AM MST Monday for
     WYZ106-110.

     Blizzard Watch from Monday morning through Monday evening for
     WYZ110.

     High Wind Warning from 5 PM this afternoon to 8 AM MST Monday
     for WYZ116-117.

NE...None.
&&

$$

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



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