Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 222326
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
426 PM MST Sun Jan 22 2017

.SHORT TERM...(This evening through Monday night)
Issued at 320 PM MST Sun Jan 22 2017

Quiet weather this afternoon will begin to change tonight as a
Pacific storm system...currently off the Oregon
coastline...redevelops over Wyoming and the eastern plains late
tonight. Models are in much better agreement with the position and
movement of the low pressure system with only some slightly
differences in timing and how far south the low develops. Models
are trending more progressive with no particular solution showing
the system digging southward and slowing down. There are some
differences with the ensemble runs with a noticeable high standard
deviation to the east...likely suggesting the system may move even
faster than previously thought. Started increasing POP this
evening for Carbon and portions of Albany counties. Do not expect
the steadier snowfall to arrive until early Monday morning across
the valleys. Went with a Winter Weather Advisory for the
mountains. Current thinking is periods of snow with 3 hour lulls
in between individual shortwaves are expected which may limited
overall accumulation and impacts as the storms energy translates
eastward. Will have to keep an eye on the valleys of Carbon county
and the foothills of the Snowy Range for potential travel impacts
tonight through Monday night. As of right now...it appears
accumulating snowfall will come in bursts with long stretches of
no snow at all.

Further east...the cold front will provide enough llvl lift for
snow shower activity on Monday and Monday evening. This is where
timing differences are key as the ECMWF shows a quick inch or two
of snow along the I80 corridor Monday evening while the other
models show mainly dry conditions with a brief band of rain/snow
moving through during the afternoon. The storm will begin to
intensify on Tuesday across South Dakota and Nebraska with
moderate to potentially heavy snow possible. Confidence is
increasing for 4+ inches of snowfall across the northern
panhandle of Nebraska late Monday night with winds over 20 knots.
Issued a Winter Storm Warning for the Chadron area and northern
Sioux county beginning late Monday night after midnight. Believe
this area has the best chance to see Winter Storm conditions with
strong winds and the potential for blowing snow in addition to
moderate to heavy snow at times. However...there is some concern
with the wind direction and snow shadowing from the Black Hills
which may limit snow accumulations. Upper level dynamic are not
favorable as well with the jet stream pushing southeast at this
time. Further south...expect winds off the pine ridge to provide
enough downslope to limit steady snowfall...although an advisory
is possible. Everywhere else...generally expect 1 to 3 inches of
snow with less than an inch across the southern NE panhandle.

.LONG TERM...(Tuesday through Sunday)
Issued at 208 PM MST Sun Jan 22 2017

Cyclonic flow aloft continues overhead and with a moist
atmosphere, most locations will continue to see light snow, though
coverage should decrease in the afternoon as the best lift decreases
over our counties. Continued cold with cloud cover and falling snow.

Wednesday...Temperatures about the same as Tuesday with little
change in thicknesses or 700 mb temperatures along with plenty of
cloud cover. Aside from some orographic snow showers over our Snowy
and Sierra Madre Ranges in moist northwest flow aloft, it will be
dry.

Thursday...Cool, cyclonic flow aloft continues keeping the cold air
reinforced over our counties and high temperatures look to be
similar to those of Wednesday.

Friday...Slow warming trend continues, limited by the northerly
flow aloft.

Saturday...Temperatures about 5 degrees warmer than Friday, although
warming trend again limited by the northerly flow aloft. Continued
dry with limited low and mid level moisture.

Sunday...Flow aloft backs to northwest and based on thicknesses and
700 mb temperatures, we will see a slow warming trend continuing,
though it will be breezy to windy based on projected low and mid
level gradients.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 423 PM MST Sun Jan 22 2017

Wyoming TAFS...VFR prevails, except at Rawlins where MVFR
develops from 04Z to 09Z, then IFR after 09Z.

Nebraska TAFS...VFR prevails, with near MVFR conditions from
12Z to 20Z.

&&

.FIRE WEATHER...
Issued at 208 PM MST Sun Jan 22 2017

No Fire Weather concerns through the week with temperatures near or
below normal with high relative humidities. Another round of snow
is expected Monday and Tuesday as storm system moves across the
area.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 9 PM this evening to 6 PM MST
     Tuesday for WYZ112-114.

NE...Winter Storm Watch from late Monday night through Tuesday
     evening for NEZ002-095.

&&

$$

SHORT TERM...TJT
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...TJT



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