Area Forecast Discussion
Issued by NWS Cheyenne, WY

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876
FXUS65 KCYS 211735
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1035 AM MST Sun Jan 21 2018

.UPDATE...
Issued at 1031 AM MST Sun Jan 21 2018

Starting to taper off headlines out west this morning as low
tracks into eastern Colorado. Webcams out by Rawlins looking good
and the METAR at RWL reporting unrestricted visibility. Attention
turning to tonight and Monday.

High wind guidance showing a drastic increase in winds over the
Arlington and south Laramie Range zones beginning tonight and
peaking out around 15Z Monday morning. Could be looking at 50-60
mph winds at these wind prone areas with fresh snowpack.
Definitely will need some headlines for these two zone for tonight
into Monday as travel impacts will be major.

&&

.SHORT TERM...(Today and Monday)
Issued at 443 AM MST Sun Jan 21 2018

Main concern today obviously centers on the ongoing winter storm
across the region. Latest satellite images shows closed, but
progressive low pressure just now emerging from the four corners,
very near the CO/NM stateline. Northeast of this low pressure,
nice diffluent flow was evident across the CWFA. An earlier
morning snow band produced a quick 2" per hour snowfall rate at
WFO Cheyenne, with around 3 inches currently on the ground. Thus
far areas in east-central Wyoming have fared the best, with a
general 6-8 inches observed in E-C Wyoming from Douglas to Lusk.
All in all, system remains on track, albeit slightly slower
developing than earlier models runs. This system slowing has been
a model trends over the past few days. Latest VWP from KCYS 88D
shows northeast flow of around 15 mph up to 11 kft, which has
added to moist ascent into the higher terrain across much of the
area.

Models are consistent in tracking this closed low pressure area
east along the Colorado/New Mexico border thru the day today,
reaching western Kansas by sunset tonight. LLVL northeast flow
will remain favorably upslope across the eastern plains at least
thru the morning hours, before turning north this afternoon and
gradually to the northwest by this evening. As such, expect
snowfall rates to be the greatest this morning, with a gradual
decrease west-east this afternoon and evening. Blowing/drifting
snow will increasingly become a concern this afternoon too, as
north winds gust to between 30-40 mph across much of the eastern
plains. No significant changes to the snowfall forecast with
the morning update, with generally 2 (west) to 7 (east) inches of
additional snowfall expected during the daytime hours today. Will
keep current Winter Storm Warnings in place.

Once winds turn northwest later today & early tonight, expect snow
to come to an end from west-east. Blowing snow will continue to be
a concern, especially along the I-80 corridor from the I-80 Summit
east to Sidney overnight, with gusts of 30 mph continuing.

Monday will be mostly dry (exception of small snow chances in the
mountains) with high temperatures returning to near freezing.

.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 12Z TAFS through 12Z Monday morning)
Issued at 443 AM MST Sun Jan 21 2018

IFR to periodic LIFR conditions expected to persist at all
airports for much of today before things start to clear out
tonight as the low pressure system to the south moves east.
Strongest winds today and tonight will be along and east of the
Laramie Range, and some blowing snow issues could be seen at
Cheyenne, Sidney and Alliance.


&&

.FIRE WEATHER...
Issued at 443 AM MST Sun Jan 21 2018

Ongoing winter storm will keep a lid on any fire weather concerns
for the foreseeable future. Otherwise, a cold start to the week
with high temperatures hovering around freezing Monday-Tuesday,
warming to the 40s for Thursday. 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 until 6 PM MST this evening for WYZ107-108-
     117-118.

     Winter Storm Warning until 11 PM MST this evening for WYZ119.

     Winter Storm Warning until 2 PM MST this afternoon for
     WYZ101>103-106-112-114>116.

NE...Winter Storm Warning until 6 PM MST this evening for NEZ002-003-
     019-095-096.

     Winter Storm Warning until 11 PM MST this evening for NEZ020-021-
     054-055.

&&

$$

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



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