Area Forecast Discussion
Issued by NWS Cheyenne, WY

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875
FXUS65 KCYS 071157
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
457 AM MST Wed Dec 7 2016

.SHORT TERM...(Today through Thursday Night)
Issued at 431 AM MST Wed Dec 7 2016

Snow continues across much of the area early this morning as the
shortwave trough moves overhead. Main band of snow is situated
from the southern Laramie Range northeast following US-85, and
spreading east into the Nebraska Panhandle. In addition, a few
snow showers in the cold core of the upper trough continue to
move over the high country out west. Sfc observations indicate
mainly light to locally moderate snowfall occurring overnight, and
webcams do show some accumulation on area roadways. With the
coldest cloud tops shifting east into Nebraska, except for a few
showers out west, think that snow will steadily diminish across
southeast Wyoming over the next few hours. Will leave the Winter
Weather Advisories as is since they seem to be in good shape
timing wise. Overall accumulations may be a bit low though due to
very cold temperatures reducing snow crystal size. Winds have
turned to the northwest and are beginning to increase, so that
may increase drifting potential through the morning. Hazardous
travel conditions will persist through at least this morning due
to snow and breezy winds, so be very careful if venturing out
today.

The Arctic push is really showing its face early this morning
as temps have dropped to the low single digits or below zero.
Wind chills are not quite within advisory levels yet, except for
a few locations here and there, but do think they`ll continue to
plummet through the early morning as winds increase. The rest of
today will be a very unpleasant day, unless you enjoy very cold
temperatures, as highs will struggle to reach 10F across southeast
Wyoming, and only slightly better readings are expected across
the panhandle. Blustery northwest winds will persist as well,
making for a very cold day. Winds will ease this evening and
overnight as strong sfc high pressure builds over the forecast
area, while skies partially clear. This will allow temperatures
to plummet below zero pretty much everywhere. The worst conditions
will be in the Laramie Valley northward to Shirley Basin.
Temperatures here will drop 20 to 25 degrees below zero, with
wind chills likely approaching 40 below. Many other locations in
the high country could see wind chills drop below minus 30, so
went ahead with a Wind Chill Watch for many locations along and
west of the Laramie Range for potentially brutally cold wind
chills. Even with wind speeds of 4 to 6 mph or so, seemingly
light, it won`t take much for frost bite to occur for humans and
animals left exposed to the cold for too long. Likely will need
another Wind Chill Advisory elsewhere for expected values in the
20 to 30 below range, but will let the day shift take care of
those highlights once the current suite expires.

There is some light at the end of the frigid tunnel as the sfc
high will push east of our area Thursday and Thursday night while
heights aloft rise. This will mean temperatures should slowly but
steadily warm during this time. In fact, Thursday night lows may
happen in the late evening out west where winds are expected to
increase as the sfc high shifts east. Temps will then steadily
rise through the night here. Should still be quite cold across
the eastern plains.

.LONG TERM...(Friday through Tuesday)
Issued at 431 AM MST Wed Dec 7 2016

Next chance of snow comes Friday as a low amplitude shortwave
moves in from the northwest...mainly across the western areas with
small accumulations in the high valleys and several inches
possible through Saturday evening in the mountains where midlevel
winds of 40 to 50 kts from the west will create decent orographic
forcing.  Models dry things out by Sunday with a chance of snow
persisting in the mountains through early next week. We do warm up
a bit starting on Friday with 20s and 30s west above 7000 ft msl
and 30s and 40s east below 7000 ft elevation for the early part of
the weekend. Behind the passing shortwave on Sunday we again tap
the cold air with teens and 20s for highs west and lower to
middle 30s for highs in the lower elevations of the east...but
with the exception of a chance of snow in the higher elevations we
remain fairly dry going into early next week with small chances of
precipitation across the east under the west northwesterly flow
aloft.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 457 AM MST Wed Dec 7 2016

Snow with MVFR ceilings and visibilities will gradually lift from
west to east this morning as the upper shortwave moves out east
onto the northern plains. Prevailing VFR conditions already being
seen at Rawlins and Laramie, with visibilities improving at
Cheyenne in the last few minutes. This trend will continue east
into the western Nebraska Panhandle areas currently seeing snow
through mid morning. Otherwise, expect winds to pick up from the
northwest this morning into the afternoon, but generally less than
25 kts. Otherwise a clearing sky expected tonight albeit with
frigid temperatures below zero many areas.

&&

.FIRE WEATHER...
Issued at 431 AM MST Wed Dec 7 2016

No Fire Weather concerns this week due to ongoing accumulating
snow and bitter cold temperatures. Slightly warmer temperatures
are expected by the end of the week before the next cold front
pushes through the region this weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Wind Chill Advisory until 11 AM MST this morning for WYZ101-102-
     104-105-107>109-111-113.

     Winter Weather Advisory until 9 AM MST this morning for
     WYZ117>119.

     Wind Chill Watch from this evening through Thursday morning for
     WYZ103>106-109-110-113>116.

     Winter Weather Advisory until 6 AM MST early this morning for
     WYZ106-110-114>116.

NE...Wind Chill Advisory until 11 AM MST this morning for NEZ002-095-
     096.

     Winter Weather Advisory until 9 AM MST this morning for NEZ054-
     055.

&&

$$

SHORT TERM...RJM
LONG TERM...JG
AVIATION...JG
FIRE WEATHER...RJM



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