Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 220545
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1045 PM MST Sun Jan 21 2018

.UPDATE...
Issued at 609 PM MST Sun Jan 21 2018

Updated forecast to expire/cancel the Winter Storm Warning along
and east of I-25 into the central and northern Nebraska panhandle.
Observations across these areas have shown a steady improvement in
visibilities. Blowing and drifting snow with periods of light snow
are expected into late this evening, but additional snow
accumulations will be minimal. Wind gusts should be mainly below
40 mph in these areas as well, so blowing snow impacts should not
be that much of a threat, although drifting snow will likely be
the main impact through tonight. Further east, will keep the
Winter Storm Warning going for the southern NE panhandle, with 1
mile visibilities and hazardous travel conditions in those areas.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 237 PM MST Sun Jan 21 2018

Moderate to heavy snow continues across the Nebraska Panhandle
this afternoon. Heaviest seems to be staying south across eastern
Colorado and extreme southeastern Nebraska/northwest Kansas. Have
been paring down warnings from west to east through the day today,
but still expecting impacts east across the Wyoming Plains and
nebraska Panhandle through remainder of the afternoon. Warnings
remain in place for these areas.

Winds are going to be an issue this evening into Monday. Snowpack
is comprised of very fine snow and is very light weight and non
compacting. By this evening, GFS showing 850mb winds out in the
Panhandle shifting to the northwest and increasing to 30-35kts.
Could see impacts from blowing snow this evening along and east of
the Laramie Range. Evening shift may want to consider a Blowing
Snow Advisory after current warnings expire.

A bigger issue for the South Laramie Range and Arlington tonight
through Monday. Craig to Casper 850/700mb gradients increasing to
around 50mtrs after 09Z tonight. Quality of the snow could create
very serious problems for travel on Interstate 80 over the Summit
and out by Arlington. Considered a Ground Blizzard Warning but
decided on issuing new Winter Storm Warnings for zones 110 and 116
(Arlington/I-80 Summit) Evening/overnight shifts may want to
upgrade once the new forecast run comes in later.

Another weak shortwave Monday evening may bring another shot of
snow out in the Snowy/Sierra Madre Ranges. Due to quick movement
of this feature, do not expect a lot of accumulation.

.LONG TERM...(Tuesday through Saturday)
Issued at 443 AM MST Sun Jan 21 2018

We note a modest warmup Wednesday into Thursday, then our next
chance at snow looks to be shaping up for Friday as an open upper
wave moves across the central Rockies. This next system does not
look to be as strong as the Colorado low we are dealing with
today.

&&

.AVIATION...(For the 06Z TAFS through Monday evening)

Most terminals across SE Wyoming have improved to VFR late this
evening as the storm system, which brought heavy snow to portions of
the area, continues to move east across the central great plains.
MVFR VIS and CIGS will continue at KSNY through midnight due to some
blowing snow and falling snow.  These conditions may linger through
early Monday morning before sunrise. Otherwise, will have to monitor
the potential of blowing snow from KRWL eastward to KLAR and even
KCYS through early Monday morning as the llvl pressure gradient
increases.

&&

.FIRE WEATHER...
Issued at 237 PM MST Sun Jan 21 2018

Minimal fire weather concerns expected next few days as widespread
snow in place from todays snow storm will remain. Cold temperatures
to keep humidity high and well above critical levels. Another cold
front and storm system will sweep across the region by the end of
the week, bringing the next chance of snow to the area.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...Winter Storm Warning from 11 PM this evening to 2 PM MST Monday
     for WYZ110-116.

NE...None.

&&

$$

UPDATE...TJT
SHORT TERM...GCC
LONG TERM...JG
AVIATION...TJT
FIRE WEATHER...GCC


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