Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 181801

Area Forecast Discussion
National Weather Service Cheyenne WY
1201 PM MDT Fri Aug 18 2017

.SHORT TERM...(Today through Sunday)
Issued at 200 AM MDT Fri Aug 18 2017

Forecast concerns in the short term continue to deal with fire
weather concerns and temperatures.

Currently...CWFA pretty much cloud-free this morning, looking at
latest infrared imagery. Surface analysis showing high pressure
covers the entire Rockies from Colorado up into northern Idaho.

Less wind today over yesterday as forecast soundings showing winds
20kts or less mixing down to the surface. Looks like the driest
day will be Saturday, when widespread afternoon humidity of 15
percent or less spreads across the CWFA. Will be highlighting
elevated fire weather conditions for Saturday across much of the
CWFA. Fortunately, winds mixing down on forecast sounding are
generally less than 20kts, so Red Flag conditions are not expected
to be widespread.

For Sunday, we should start to see an increase in humidity as
southeasterly winds return to the area. Dry backdoor cold front
looks to move into the northern Panhandle, Converse and Niobrara
Counties in east central Wyoming with slightly cooler
temperatures expected.

.LONG TERM...(Sunday night through Thursday)
Issued at 200 AM MDT Fri Aug 18 2017

Models are in general agreement at showing a shortwave trough moving
to the north of the CWA on Monday and then into the Northern Plains
by Monday night.  Will continue to fcst partly cloudy skies for
midday Monday with model RH suggesting passing mid to high lvl
clouds.  The ECMWF is an outlier with tstms developing across
eastern zones by Monday aftn in the convergence along the sfc front.
A cooler and dry day is in store for Tuesday in the post frontal
airmass.  The upper ridge will re-build over Colorado/Wyoming on
Wednesday and Thursday with warming temps.  Flow aloft does become
more southwesterly by Thursday so could see a slight increase in
subtropical moisture and PW values, resulting in a somewhat higher
chance of storms over the mtns.


.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 200 AM MDT Fri Aug 18 2017

Sunny and dry today with afternoon humidity west of the Laramie
Range falling to near 15 percent. More widespread low humidity
expected Saturday with slightly gusty winds and warmer
temperatures. Elevated fire weather concerns Saturday with
afternoon humidity dropping to the low teens out west and north
and wind gusts to 25 MPH at times. For now, will hold off on any
fire weather headlines, but if forecast winds get any stronger,
may need to issue something. Cooler temperatures and better
humidity Sunday as a front moves in from the north Sunday




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