Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 122153
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
253 PM MST Fri Jan 12 2018

.SHORT TERM...(This evening through Sunday)
Issued at 250 PM MST Fri Jan 12 2018

Early afternoon water vapor imagery showed an upstream upper ridge
axis along the West Coast and downstream upper trough axis over the
MS Valley. A potent shortwave was tracking southeast into the central
Great Plains, with a vort lobe to the northwest into central WY. A
quasi-stationary surface front extended from southwest MT through
southeast WY and south over the eastern CO plains. Low/mid level
instability with proximity to the surface frontal convergence has
resulted in banded snow showers oriented NW-SE over southeast WY
and the SW corner of the NE Panhandle. With the relatively fast
motion of the showers, snow amounts have been light. However, gusty
NW-N winds up to 35 mph accompanying the showers will produce blowing
snow and reduced visibility through the rest of this afternoon.
Mountain snow totals ranged from 6-12 inches for the Sierra Madre
Range, to as much as two feet over the Snowy Range.

Short range model/ensemble guidance is in good agreement this weekend
with the upper ridge amplifying from the Great Basin into western
Canada, and downstream upper ridge nearly stationary over the eastern
half of the CONUS. The result will be a prevailing northwest flow
aloft over the CWFA. Occasional light snow will continue over the
Snowy/Sierra Madre ranges tonight, with an additional one to two
inches. Generally dry conditions are forecast Saturday and Sunday
with above normal high temperatures in the 30s and 40s outside
the mountains. Low temperatures by Saturday morning will range
from the single digits and lower teens over western NE to the mid
teens to mid 20s elsewhere. Lows by Sunday morning will moderate
into the 20s for the plains as the frontal boundary shifts to the
east. CAG-CPR 700/850mb height gradients remain in the 30-40m
range this weekend, promoting breezy to windy periods over the
southeast WY wind prone areas.

.LONG TERM...(Sunday night through Friday)
Issued at 250 PM MST Fri Jan 12 2018

An Arctic cold front will sink south across much of the CWA Sunday
night with an area of snow likely occurring just behind the front.
Not much in the way of upper support, thus snowfall amounts should
stay light. A cold day Monday especially over the plains with high
in the teens to around 20, and this may be a bit warm if the surface
high settles more southward. Any lingering light snow/flurries should
end by late in the day. The cold surface high will pull away Tuesday
with upper ridging building into the region, with a dry and warmer
period expected Tuesday through Thursday. Next upper trough moves
into the western CONUS Friday and could bring some rain and snow
showers to western parts of the CWA by late in the day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday morning)
Issued at 1021 AM MST Fri Jan 12 2018

Snow showers will affect the area from KRWL to KCYS early before
ending. Sctd MVFR/IFR cigs through this afternoon mainly for the
Panhandle terminals. Should see mainly VFR tonight into Saturday
morning.

&&

.FIRE WEATHER...
Issued at 250 PM MST Fri Jan 12 2018

No fire weather concerns this weekend into much of next week with
non-critical fuels and humidities. It will be breezy to windy for
much of southeast Wyoming this weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 5 PM MST this afternoon for WYZ114.

     Winter Weather Advisory until 5 PM MST this afternoon for WYZ112.

NE...None.
&&

$$

SHORT TERM...MAJ
LONG TERM...RE
AVIATION...RE
FIRE WEATHER...MAJ



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