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Area forecast discussion 
National Weather Service Cheyenne Wyoming
408 PM MST Wednesday Nov 25 2015

Short term...(this evening through Thursday night)
issued at 407 PM MST Wednesday Nov 25 2015

Areas of freezing fog and drizzle have become quite prevalent in the
southern Laramie range foothills including I-80 between Cheyenne and well as I-80 between Laramie and Elk Mountain. Road
temperatures have dropped below zero over the past few hours while
air temperatures are in the teens. Thus...think these areas will
begin to ice accumulation on various surfaces soon so started the
highlights now for these three zones. Once snow begins to fall later
this evening...roads could become extremely slick with the
combination of ice accumulation and snow...hence the upgrade of the
southern Laramie range foothills inclusion into the Winter Storm
Warning. Start time for remaining highlights was bumped up to 5 PM
to account for the earlier start time of fog/drizzle impacts over
The Summit.

Otherwise...forecast looks to be in good shape since the previous
update. Upper level lift will continue to increase over the forecast
area this evening which will strengthen easterly upslope winds and
general broadscale lift for precipitation production. Frontogenesis will
strengthen overnight as well...while midlevel moisture deepens from
north to south tonight. Thus...expect change over of any mixed
precipitation to light snow overnight with snow rates increase especially
along and west of a line from Lusk to Cheyenne. Light snow will
continue on Thanksgiving over much of the forecast area...along with
very cold temperatures. Gusty east-northeast winds will develop over
the I-80 Summit and eastern foothills...along with western Carbon
County to produce concerns with blowing snow. Drier air filtering in
from the north should shut off snow production Thanksgiving night.
Bitterly cold temperatures with wind chills well below zero will
settle in for early Friday morning.

Long term...(friday through tuesday)
issued at 330 am MST Wednesday Nov 25 2015

Friday...cold upper trough continues to remain nearly stationary
over southern Nevada with cold surface high pressure entrenched over
our counties. Slight chance of light snow over the southern half of
our counties with adequate low and middle level moisture and weak
upward vertical motion primarily due to upslope. Continued quite
cold with fresh snowpack...700 mb temperatures near -11 celsius and
cloud cover. lobe of the upper low rotates across eastern Wyoming
producing a few snow showers. Continued cold per prognosticated 700 mb cover and snowpack.

Sunday...upper trough lifts into the northern rockies and northern
plains states with our flow aloft turning southwest helping for a
slight warming trend. Still though enough residual cloud cover and
orographics for scattered snow showers over our snowy and Sierra
Madre ranges...dry elsewhere.

Monday...pesky upper trough rotates across either the
per the GFS...or over Nebraska...per the European model (ecmwf). In either
case...cold temperatures aloft will promote at least isolated snow
showers over our counties with temperatures remaining quite
cold...and perhaps even colder than our current forecast indicates.

Tuesday...finally...a return to slightly warmer weather as the flow
aloft backs to west or northwest allowing surface Lee troughing to
strengthen and helping a moderation in the cold airmass.


Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1127 am MST Wednesday Nov 25 2015

Areas of freezing drizzle are expected this evening over the High
Plains of southeast Wyoming and the western NE Panhandle...changing to
snow overnight. Meanwhile...snow will continue to spread eastward
across the area this afternoon through tonight. Widespread MVFR to
IFR conditions will persist through this afternoon...with IFR to
LIFR ceilings/visibilities becoming likely for most terminals overnight through
Thursday. The worst conditions will be along/west of the Laramie
range with stronger winds/heavier snow. Visibilities may be under
a half mile at times at krwl and klar in snow and blowing snow.
Mountains will be obscured through the taf period.


Fire weather...
issued at 407 PM MST Wednesday Nov 25 2015

No fire weather concerns anticipated in the near term due to snow
through the end of the week...and very cold temperatures through the


Cys watches/warnings/advisories...
Wyoming...Winter Weather Advisory until 5 PM MST Thursday for wyz102.

Winter Storm Warning until midnight MST Thursday night for

Winter Weather Advisory until midnight MST Thursday night for

Winter Storm Warning until 5 PM MST Thursday for wyz101.

Winter Storm Warning until midnight MST Thursday night for

NE...Winter Weather Advisory until 5 PM MST Thursday for nez019>021-



Short term...rjm
long term...Rubin
fire weather...rjm

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