Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 180526
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1026 PM MST Wed Jan 17 2018

.SHORT TERM...(This evening through Friday night)
Issued at 220 PM MST Wed Jan 17 2018

Tonight...Northwest flow continues, with strengthening flow
aloft, leading to increase winds at the surface. This is also noted
in the 850 mb Craig to Casper height gradient increasing to 54
meters by dawn Thursday.  Thus will accordingly boost winds at wind
prone locations. Not as cold as this morning with the airmass
modifying.

Thursday...Significant warming trend expected as the flow aloft
backs from northwest to west, inducing an even stronger surface lee
trough. With 700 mb temperatures near 5 Celsius, and downslope
winds, expect high temperatures to rise into the upper 40s to near
60 degrees at lower elevations.

Thursday night...The flow aloft strengthens even more significantly
with the 850 mb Craig to Casper height gradient peaking at 66 meters
by Friday morning. With around 50 knots of mid level winds and
strong boundary layer winds progged, we will issue a High Wind Watch
for our typically wind prone locations.

Friday...Strong southwest flow aloft continues with periods of
middle and high level cloudiness anticipated ahead of the next
approaching shortwave trough aloft. Compromised between the NAM and
GFS MOS maximums for high temperatures. Atmosphere still too dry to
support any precipitation.

Friday night...Next cold front will surge southward into our
northern counties, and with deepening moisture and upslope low level
winds, expect chances for snow to increase, especially over and
near the Snowy and Sierra Madre Ranges.

.LONG TERM...(Saturday through Wednesday)
Issued at 220 PM MST Wed Jan 17 2018

Models in pretty good agreement in the progress of the winter
system affecting the area over the weekend with the GFS a little
faster than the EC. Main difficulty will be snowfall amounts
across the CWA by the time things wind down late Sunday. Snow will
spread across the CWA during the day Saturday with any rain
changing to snow by late in the day as colder air filters across
the area in response to lee cyclogenesis over southeastern
Colorado. Snow will continue Saturday night into Sunday as the
upper low moves across the CO/NM border area then taper off
gradually Sunday afternoon and evening as the surface and upper
lows move out over the central plains. Heaviest snows will be
over the mtns where over a foot looks a decent bet with a general
3 to 6 inches over the plains. Much colder and rather blustery on
Sunday. Monday through Weds looks to be on the cool side with
temps a little below seasonal averages. A couple disturbances
should also set off some snow showers at times, mainly over the
higher mtns.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1022 PM MST Wed Jan 17 2018

VFR prevails w/ SCT-BKN coverage of high-level cloud cover through
the TAF period, mainly above 15k feet AGL. Expect gusty winds over
KCYS and KRWL on Thursday afternoon, with occasional gusts between
25 and 30 knots.

&&

.FIRE WEATHER...
Issued at 220 PM MST Wed Jan 17 2018

No concerns based on humidity and wind trends.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from late Thursday night through Friday morning
     for WYZ106-110-116-117.

NE...None.
&&

$$

SHORT TERM...RUBIN
LONG TERM...RE
AVIATION...CLH
FIRE WEATHER...RUBIN



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