Area Forecast Discussion
Issued by NWS Cheyenne, WY

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110
FXUS65 KCYS 111735
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1033 AM MST Mon Dec 11 2017

.SHORT TERM...(Today through Wednesday)
Issued at 230 AM MST Mon Dec 11 2017

Winds and humidity continue to be the biggest forecast challenges
through the upcoming week with a strong winds event possible ahead
of a big pattern change next week.

Currently...We have a clipper system tracking across eastern South
Dakota this morning. A broad area of mid and high level cloudiness
over extreme northeastern Wyoming and southwestern South Dakota
this morning moving at a pretty fast rate and may be east of the
Panhandle by sunrise. A 1048mb surface high remains over southern
Idaho this morning.

Possibility of strong winds in the Panhandle today as a result of
the passing clipper system. GFS 850mb winds up to 40kts across the
Panhandle today after 18Z. Expecting wind gusts to 50mph out that
way this afternoon...especially over the southern Panhandle. 700mb
temperatures fall from +1C this morning to -7C over the northern
Panhandle by 18Z and 850mb temperatures falling 4-5 degrees C
through the morning hours. Will certainly help to keep humidity a
little higher today and have decided on holding off on any fire
headlines today.

Winds ease this evening after sunset with 850mb winds down to
25kts by 06Z tonight across the Panhandle. More westerly 700mb
winds will begin to warm up 700mb temperatures for Tuesday with
GFS 700mb temperatures back above freezing across the CWFA.

Next clipper system set to impact the Panhandle and areas east of
the Laramie Range Wednesday morning. Still dry, but increasing
winds again during the day Wednesday.

.LONG TERM...(Wednesday night through Sunday)
Issued at 230 AM MST Mon Dec 11 2017

Wednesday night/Thursday...Weak shortwave trough aloft sweeps across
our counties producing isolated to scattered snow showers over and
near our Northern Laramie, Snowy and Sierra Madre Ranges, dry
elsewhere Wednesday night. Windy and seasonably cool on Thursday
with 700 mb temperatures near -7 Celsius yielding maximum
temperatures from the mid 30s to mid 40s.

Friday...Marks the beginning of a long period of quite windy days as
the flow aloft backs to northwest and strengthens. Although
temperatures will be warmer due to strong downsloping winds and 700
mb temperatures near -2 Celsius, it will be quite windy based on
expected low and mid level gradients.

Saturday...Fast moving and low amplitude shortwave trough aloft
sweeps across our counties producing a chance of rain and snow
showers across our northern counties as well as over the Snowy and
Sierra Madre Ranges. Definitely cooler and quite windy based on
projected Craig to Casper 850/700 mb height gradients.

Sunday...Perhaps slightly warmer based on thicknesses, although
still quite windy per progged surface through 700 mb gradients and
the Craig to Casper 850/700 mb height gradients.

&&

.AVIATION...(For the 18Z TAFS through Tuesday morning)
Issued at 1032 AM MST Mon Dec 11 2017

VFR conditions through tonight. Midlevel cloudiness across the far
eastern plains will dissipate this evening. Very windy conditions
are expected across the far eastern SE Wyoming plains and western
Nebraska, where gusts between 30 to 40 kts are expected this
afternoon and into early this evening. Winds will be light after
03z.

&&

.FIRE WEATHER...
Issued at 230 AM MST Mon Dec 11 2017

We look to get a little reprieve in fire weather conditions today,
but winds will be strong across the Nebraska Panhandle. A Clipper
system, tracking into eastern South Dakota will drop a backdoor
cold front into areas east of the Laramie Range through the
morning hours. This front will bring mid and upper level clouds to
the Panhandle along with colder temperatures. So afternoon
humidity is expected to stay above critical levels today. Winds
ease some Tuesday before the next Clipper system moves into our
eastern zones Wednesday. A change in the overall weather pattern
expected next week as a wetter pattern looks to set up as early as
next weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

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



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