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000 
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.
&&

$$

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