Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 140035

Area Forecast Discussion
National Weather Service Cheyenne WY
635 PM MDT Fri Oct 13 2017

.SHORT TERM...(This evening through Saturday)
Issued at 207 PM MDT Fri Oct 13 2017

Pretty quiet afternoon across the CWA with west to southwest flow
aloft and minimal cloud cover. Getting some southwest wind gusts
to 35-40 mph in the Arlington area, however should see these winds
decrease by late aftn and evening with the loss of daytime mixing.
Progressive shortwave trough is still progged to move from
northeast Oregon this aftn to western Nebraska by Saturday
afternoon. Fropa will occur on Saturday morning, with a blustery
day in store. With 700-mb temps dropping to -7C to -9C by midday,
highs will struggle to get out of the 40s over much of the CWA. The
GFS is really the only model that shows winds more west-
northwest behind the front, as opposed to northwest/north from the
other models. Kept the wind forecast more in line with the
NAM/ECMWF as opposed to the stronger GFS. The other story with
this quick hitting system will be the brief period, from 12-18Z,
where snow showers will be possible over mainly north and western
zones. Due to the brief duration of precip, snow accumulations
will generally remain below 1-2 inches over lower elevations.

.LONG TERM...(Saturday night through Thursday)
Issued at 218 AM MDT Fri Oct 13 2017

Saturday night...Progressive shortwave trough aloft moves from
western Nebraska into the Mississippi Valley with strong Northwest
flow aloft over our counties. Progged gradients suggest breezy
conditions over and near our wind prone locations.

Sunday...Flow aloft remains northwest with breezy to windy
conditions expected due to deep unidirectional flow aloft. Decent
warming trend as 700 mb temperatures and 1000-500 mb thicknesses
rise significantly.

Monday...Nice warming trend continues with rising mid level
temperatures and thicknesses. Continued dry with minimal low and mid
level moisture.

Tuesday...Ridge aloft moves overhead, inducing a surface lee trough
to develop across far eastern Wyoming. Warming trend continues with
700 mb temperatures continuing to rise and with airmass modification.

Wednesday...Mild temperatures continue with zonal, west to east,
flow aloft. Downslope warming will also help high temperatures.

Thursday...The flow aloft turns southwest in advance of the next
approaching shortwave trough aloft. Continued dry with lack of low
and mid level moisture.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 635 PM MDT Fri Oct 13 2017

Two main concerns to area terminals over the next 24 hours. The
first will be the potential for -SHSN after 12z at KRWL and after
15z at KLAR as a cold front pushes through the area. At this
point, am not convinced snow will be all that widespread nor
impactful, so have maintained the VFR thinking for these sites.
Will need to take another look at new information here this
evening to see if we need to lower conditions with 06z TAF update.
The second concern will be the potential for BR/FG at KAIA and
KSNY. Latest info suggests at least the potential, so felt it
prudent to add for this issuance 09-15z. Another breezy day in
store with WNW 25G35KT behind the front.


Issued at 207 PM MDT Fri Oct 13 2017

Elevated to critical fire weather conditions will continue to impact
areas along and west of the Laramie Range through this afternoon.
Humidity values will remain around 15 percent with gusts to 25 to 30
mph.  No Red Flag Warning will be issued however with webcams showing
patches of snow still on the ground from this past storm.  After a brief
cooldown this weekend, temperatures will rise to above normal through
the middle of next week.




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