Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 182134

Area Forecast Discussion
National Weather Service Cheyenne WY
334 PM MDT Fri Aug 18 2017

.SHORT TERM...(This evening through Monday)
Issued at 330 PM MDT Fri Aug 18 2017

Current Satellite loop shows mainly clear skies across Wyoming
with little in the way of cloud cover or weather. Believe this
trend will continue into Saturday with partly cloudy skies further
south near the Colorado border and maybe a thundershower or two
along and south of I-80. Kept POP pretty low and mainly between 10
to 20 percent in this area due to dry air aloft and limited CAPE
through the afternoon. Slightly more favorable environment on
Sunday as a weak upper level shortwave moves slowly across
southeast Wyoming and western Nebraska. Increased POP from the
mountains over towards Cheyenne for isolated showers and
thunderstorms. Coverage should be limited into the evening hours
due to dry air aloft and weak forcing. High temperatures will be
above normal this weekend with highs in the 80`s across most of
the region and low 90`s across western Nebraska.

Forecast for Monday looks on track with the eclipse, although
there seems to be a slightly more favorable environment for
thunderstorms in the afternoon across the high plains. Thankfully,
these thunderstorm are expected to form after the eclipse. Partly
cloudy skies are still expected with the pattern favoring high
clouds, but some midlevel clouds are possible as well and will
need to be monitored. Sky coverage appears to be between 30 to 45
percent between 9 am to 2 PM. Models have been pretty consistent
about this although the GFS and ECMWF have trended slightly higher
on coverage of clouds due to a cold front approaching the area
from the north. Timing of the convection, along with the position
of the frontal boundary to the north, will be the main forecast
concerns going into the weekend and early on Monday.

.LONG TERM...Monday Night through Friday...

In general, upper-level ridging will prevail across the region for
much of the extended forecast period. Minimal H7-H3 RH combined w/
a lack of a substantial disturbance aloft should promote little/no
chance for precipitation outside of the mountains through at least
Thursday. The ECMWF/GFS are in fair agreement with a fairly potent
mid-level shortwave traversing the flow during the Thursday Night/
Friday time frame, so expect this to be the best opportunity for a
more widespread shower/thunderstorm threat. Otherwise, expect day-
time highs to be near seasonal norms w/ highs generally in the 80s
for most lower elevation areas.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1159 AM MDT Fri Aug 18 2017

VFR conditions will prevail today across southeast Wyoming and the
western Nebraska Panhandle. West winds gusting as high as 25 knots
can be expected at KRWL this afternoon.


Issued at 242 PM MDT Fri Aug 18 2017

Moderate to elevated Fire Weather concerns this weekend and into
Monday with dry weather, warm temperatures, and low relative
humidities. The best potential for critical Fire Weather
conditions will be Saturday afternoon west of Interstate 25 as
winds gust around 25 MPH. Humidities will begin to increase by
late Sunday and Monday as some moisture moves into the area with
slightly cooler temperatures.




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