Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 140907

Area Forecast Discussion
National Weather Service Cheyenne WY
307 AM MDT Wed Mar 14 2018

.SHORT TERM...(Today through Friday)
Issued at 307 AM MDT Wed Mar 14 2018

Lots going on weather wise in the Short Term. Forecast challenges
deal with snow amounts and winds Thursday night through Friday.

Currently...Water vapor imagery showing a pretty strong low
pressure system off the coast of Oregon this morning. 100+ knot
jet on the back side of this low should keep the low digging south
towards California this morning. IR imagery showing clear skies
over southeast Wyoming and Nebraska Panhandle this morning. Some
high clouds starting to move into western Wyoming.

For today, looking at a pretty nice day as high pressure remains
in control of the weather. Still looking at widespread low to mid
60s across southeast Wyoming and upper 60s/low 70s across the
Nebraska Panhandle. Expect increasing clouds through the day, but
overall a Chamber of Commerce day for this part of the country.

The weather begins to change Thursday as that low moves into
western Colorado. Should see precip begin breaking out across
Carbon County late Thursday morning. SPC has us in a General
Thunderstorm outlook in their Day 2 Outlook. Seeing lifted indices
of -1 to -2C across the Panhandle and parts of southeast Wyoming
Thursday afternoon, so we could see a few rumbles of thunder in
the afternoon.

By Thursday evening, the upper low is forecast near Colorado
Springs. Decent upper level diffluence over southeast Wyoming and
Nebraska Panhandle. Models in great agreement in QPF positioning,
so confidence is high that we are going to see widespread
precipitation over the CWA Thursday night. 700mb temperatures fall
to -8 to -10C over southeast Wyoming with rain turning over to
snow by mid evening or so.

700mb winds on the increase behind the low pressure system. GFS
forecasting 50-55kts across Carbon and Albany Counties after 06Z
Friday. Local high wind guidance showing Craig to Casper 850/700mb
height gradients increasing above 50mtrs by 06Z Friday as well,
peaking out at 67/56 mtrs respectively by 12Z Friday. Decided on a
High Wind Watch for Arlington and the Laramie Valley for Thursday
evening as this happens. Bordeaux and South Laramie Range winds
will likely materialize a little later (say 12Z Friday).

Snow wise, its looking like the northern Nebraska Panhandle and
Niobrara County will see the bulk of the snow. Getting snow
amounts up to 8 inches up there through the event. So after
coordination with LBF and UNR offices, went with a Winter Storm

Question on the south Laramie Range. Less snow forecast here, but
much stronger winds could pose a problem up there. Was going to go
with a High Wind Watch, but decided on a Winter Storm Watch for a
combination of snow and wind. Day shift can take another look at
the 12Z guidance and determine which way to go this afternoon.

.LONG TERM...(Friday night through Tuesday)
Issued at 307 AM MDT Wed Mar 14 2018

Lull in the weather Friday night into Saturday as a short upper
ridge moves by with milder temperatures returning on Saturday.
Some snow showers should return to western areas Saturday night
as the next upper trough approaches the CWA. Models diverge on the
track of the system Sunday with the GFS to the north of the CWA
and the EC to the south. This will impact pcpn/temps over the
plains Sunday with the EC colder and bringing another round of
snow while the GFS remains dry and mild. Will lean more towards
the wetter EC for now. System moves away Sunday night with Monday
and Tuesday looking mainly dry and a bit on the cool side under
northwesterly upper flow.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 307 AM MDT Wed Mar 14 2018

VFR through the period with some increase in mainly high clouds
later today through tonight. It will be breezy this afternoon at
Rawlins with gusts to 25 kt.


Issued at 307 AM MDT Wed Mar 14 2018

Warm and dry today as high pressure remains over the area.
Temperatures today climbing into the 60s and low 70s with
afternoon humidity falling to the upper teens. Fortunately, winds
are expected to be light, mitigating any fire weather concerns.
Weather changes Thursday as a low pressure system tracks across
Colorado. Expecting increasing chances for rain and mountain snow
as Thursday progresses. Snow Thursday night into Friday for all


WY...Winter Storm Watch from late Thursday night through Friday
     afternoon for WYZ102.

     High Wind Watch from late Thursday night through Friday morning
     for WYZ110-115.

     Winter Storm Watch from Thursday evening through Friday morning
     for WYZ116-117.

     High Wind Watch from Friday morning through Friday afternoon for

NE...Winter Storm Watch from late Thursday night through Friday
     afternoon for NEZ002-003-095-096.



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