Area Forecast Discussion
Issued by NWS Cheyenne, WY

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520
FXUS65 KCYS 171744
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1044 AM MST Tue Jan 17 2017

.UPDATE...
Issued at 928 AM MST Tue Jan 17 2017

We sent out a quick update to lower wind speeds in Arlington this
afternoon. The high wind speeds near Bordeaux are a result of
stronger winds around 750mb upstream blowing through the gap just
west of Bordeaux. This in combination with the good pressure falls
to the northeast of the forecast area should keep the wind speeds
fairly steady around Bordeaux this afternoon.

&&

.SHORT TERM...(Today through Thursday)
Issued at 245 AM MST Tue Jan 17 2017

Forecast concerns in the short term deal with fog and winds. Long
term...could be seeing a significant snow event for beginning of
next week.

Currently...1038mb surface high over western Wyoming this
morning. Skies pretty much clear over southeast Wyoming and
Nebraska Panhandle. This has lead to some pretty cold temperatures
over our western zones. Rawlins and Laramie down to 1 below zero,
Saratoga down to 2 below zero. Patchy dense fog being reported at
Laramie. Looks pretty confined, so have held off on a Dense Fog
Advisory for the time being. If it becomes more widespread, may
need to issue one later though.

Dry day today with the surface high dominating the weather. High
should stay in place for next 24 hours or so with upper ridge axis
passing overhead tonight into Wednesday morning. Did go with
persistence and brought fog back into the Laramie Valley tonight.

Winds on the increase Wednesday afternoon into Thursday. Craig to
Casper gradients on both the GFS and NAM climb to 50mtrs by 18Z
Wednesday at 850mbs. So the wind prone areas likely to see gusts
to +50MPH...especially the Bordeaux area. Looks pretty warm for
Wednesday as well with 700mb temperatures climbing to +6C. Should
see highs east of the Laramie Range in the 50s.

.LONG TERM...(Thursday Night through Tuesday)
Issued at 245 AM MST Tue Jan 17 2017

By Thursday night models show a series of shortwaves working
northeast across Wyoming into western Nebraska with increasing
midlevel winds around 40 kts. Increased midlevel winds with
increasing moisture tap from the southwest will spell increasing
chances for orographic snow in the Sierra Madre and Snowy Ranges
initially for the early weekend...but remaining dry farther east
onto the plains. By late Monday both the GFS and ECMWF are showing
a low pressure system deepening across eastern colorado...tracking
east northeast into southern Nebraska through Tuesday. Both the
GFS and ECMWF are fairly progressive with the track of the low so
major snowfall totals don`t appear likely given the current
projections, but several inches of snowfall over a 12 hour period
certainly possible if the models are right. This far out forecast
changes for early next week are likely, either way. Just something
to take note of for now.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1044 AM MST Tue Jan 17 2017

Stratus has cleared at KLAR this morning, with VFR conditions
expected through today. Continue to think stratus/fog will return
tonight in the Laramie Valley within light winds and a moist
boundary layer, so maintained VLIFR TAF for KLAR after 04Z,
continuing during the overnight period. VFR conditions are
expected at the remaining terminals with breezy conditions mainly
at KRWL this afternoon.

&&

.FIRE WEATHER...
Issued at 245 AM MST Tue Jan 17 2017

Drier weather pattern for this week with increasing winds for the
wind prone areas of southeast Wyoming. By Wednesday, the wind
prone areas could be seeing gusts to 50 MPH that could persist
into Thursday. With existing snowpack though, fire weather
concerns will be minor. Looks like a pretty widespread snow event
for next Monday and Tuesday is possible across the area.

&&

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

$$

UPDATE...REC
SHORT TERM...GCC
LONG TERM...JG
AVIATION...RJM
FIRE WEATHER...GCC



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