Area Forecast Discussion
Issued by NWS Cheyenne, WY

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105
FXUS65 KCYS 130532
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1032 PM MST Thu Dec 12 2019

.SHORT TERM...(This evening through Saturday night)
Issued at 122 PM MST Thu Dec 12 2019

Tonight...Moist northwest flow aloft continues, helping to produce
widespread orographic snows over our Snowy and Sierra Madre Ranges,
thus the current Winter Storm Warning looks warranted. Low and mid
level gradients also look sufficient for locally strong wind gusts
to continue overnight in the Arlington, Elk Mountain and over the
Southern Laramie Range and I-80 Summit, so will continue the High
Wind Warning there. Otherwise, a quiet night expected.

Friday...In the wake of a fast moving and low amplitude shortwave
trough aloft passage, the low and mid level gradients will
strengthen, producing a windier day, primarily west of a Douglas to
Cheyenne line, with the High Wind Warning continuing for Arlington
and the I-80 Summit. Orographic snows should decrease somewhat in
the afternoon, thus allowing the Winter Storm Warning to end.
Temperatures will be somewhat cooler in the wake of a passing cold
front.

Friday night/Saturday...Another slow moving and low amplitude
shortwave trough aloft moves across our forecast area, and combined
with adequate low and mid level moisture, will produce scattered to
numerous snow showers, most numerous over the mountains. Will also
see colder temperatures as low and mid level temperatures fall
significantly.

.LONG TERM...(Sunday through Thursday)
Issued at 122 PM MST Thu Dec 12 2019

Sunday...Continued cold with a broad trough aloft over the Rockies
and 700 mb temperatures only near -14 Celsius. As the bulk of the
energy aloft moves off to our south over Colorado, chances for snow
will significantly decrease.

Monday...Even colder as heights aloft lower even more and 700 mb
temperatures fall to near -16 Celsius under brisk northwest flow
aloft, producing a breezy to windy day.

Tuesday...Will see a slow warming trend as heights aloft rise and
700 mb temperatures climb to near -9 Celsius under dry northwest
flow aloft.

Wednesday...The warming trend continues as the ridge aloft moves
overhead and flattens with the flow aloft becoming zonal, inducing
surface lee troughing and downslope warming west winds.

Thursday...As a weak and low amplitude shortwave ridge aloft moves
overhead, then flow aloft will turn southwest, with temperatures
about the same as those on Wednesday. Continued dry with limited low
and mid level moisture.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1024 PM MST Thu Dec 12 2019

KRWL still anticipated to fluctuate between MVFR/IFR overnight as
lingering snow showers from nearby mountains will create
occasional low cigs. VFR for KCYS and KLAR overnight expected.
Gusty winds of 20-30 knots also anticipated at times at WY
terminals. Panhandle terminals will have VFR conditions and
experience winds 10-15 knots at times. Added in the mention of
VCSH and -RA to KBFF and KSNY respectively as they will see light
precipitation the next couple of hours through approximately 9Z.
This is evidenced off latest microphysics nighttime satellite and
radar observations, in addition to the METARS. BKN to OVC skies
at the Panhandle terminals will remain overnight.

&&

.FIRE WEATHER...
Issued at 122 PM MST Thu Dec 12 2019

No concerns based on expected winds and humidities.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until noon MST Friday for WYZ112-114.

     High Wind Warning until 6 PM MST Friday for WYZ110-116.

NE...None.
&&

$$

SHORT TERM...RUBIN
LONG TERM...RUBIN
AVIATION...BW
FIRE WEATHER...RUBIN



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