Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 180428

Area Forecast Discussion
National Weather Service Cheyenne WY
1028 PM MDT Thu Aug 17 2017

Issued at 808 PM MDT Thu Aug 17 2017

Isolated convection that developed this afternoon will dissipate
after sunset in the wake of a departing shortwave. Skies will be
partly cloudy tonight with seasonal temperatures. A warm and dry
air mass will prevail Friday, with breezy southwest winds after
noon west of the Laramie Range.


.SHORT TERM...(This evening through Saturday night)
Issued at 330 PM MDT Thu Aug 17 2017

Isolated thunderstorms from earlier this afternoon have pushed
southeast into Colorado. Expected brief scattered rain showers and
an isolated thundershower into this evening as an upper level
disturbance, currently over northeast Wyoming, continues to
rapidly move eastward through tonight. Most of this activity
should be confined to the I-80 corridor and diminish shortly
after sunset. Once the upper level disturbance moves east into the
northern plains, warmer and drier air aloft will move over the
forecast area. This drier air aloft will greatly suppress
convective activity on Friday and most of Saturday with high
temperatures rising into 80`s to low 90`s across the region,
warmest over the lower elevations below 4500 feet. Thunderstorm
activity is slightly more favorable on Saturday near the Colorado
border as some moisture will return due to backing winds from the
south and southeast.

.LONG TERM...(Sunday through Thursday)
Issued at 242 PM MDT Thu Aug 17 2017

The main weather concern for Eclipse Day (Monday) will be a threat
for mid/high level cloud cover. The models continue to show decent
H7-H3 RH values across the CWA, suggesting at least periodic shots
of moisture embedded within southwest flow aloft. We may also have
some remnant shower activity early Monday morning which could lead
to the potential for lingering cloud cover. We have maintained the
Partly Cloudy wording along the Path of Totality based on forecast
soundings relatively dry below 300 mb. A couple of mountain storms
are possible in the afternoon, but overall do not expect any major
weather impacts to travelers on Monday. Precipitation chances Tue/
Wed are challenging, with the GFS/ECM disagreeing on the placement
of the shortwave ridge axis. There is potential for each afternoon
and/or evening to be fairly active though if southwesterly mid-lvl
flow is able to take control.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1026 PM MDT Thu Aug 17 2017

VFR. Winds gusting 20 to 23 knots at Cheyenne, Rawlins,
Scottsbluff and Alliance from 15Z to 01Z.


Issued at 242 PM MDT Thu Aug 17 2017

Low Fire Weather concerns will continue late this week with
moderate concerns likely this weekend due to low humidities and
some gusty winds across southeast Wyoming. Drier conditions with
warmer temperatures are expected Friday and this weekend with
little or no precipitation across southeast Wyoming and western
Nebraska. Any thunderstorms that do form will likely be in the
mountains this weekend. Relative Humidities will trend lower into
this weekend with values between 15 to 20 percent each afternoon.
Concerns may become elevated on Saturday in localized areas west
of Interstate 25 due to winds gusting between 20 to 25 MPH.




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