Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 172116
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
216 PM MST Fri Feb 17 2017

.SHORT TERM...(Late this afternoon through Sunday night)
Issued at 215 PM MST Fri Feb 17 2017

The afternoon water vapor loop showed upper lows over the southern
Great Plains and off the CA coast. In between, a shortwave trough
was tracking east across the northern Great Plains. A surface front
which passed through the CWA earlier this morning extended from
eastern NE through northwest KS and northwest along the Front Range
of CO/WY, then southwest into the southern Great Basin. A modest
pressure gradient resulted in breezy west to northwest winds. Visible
satellite imagery showed a large canopy of middle and high clouds
spreading northeast across UT, western CO and southwest WY. Although
not as warm as 24 hours ago, temperatures were still mild with readings
from the mid 40s to mid 60s.

There is good agreement with the 12Z/18Z short range model consensus
progging the large scale pattern to become more amplified across the
western CONUS this weekend. The eastern Pacific trough will amplify
further as it slowly moves inland through Saturday. The southwest
flow aloft will increase over the Rockies, advecting Pacific moisture
into the southern WY mountains, especially tonight and Saturday
morning. Orographic precipitation, mostly light, will develop west
of the Laramie Range. The higher mountains may receive a couple
inches of snow. Along and east of the Laramie Range will remain dry
and breezy Saturday with above normal temperatures (55-65 degrees).

There will be a slight decrease in precipitation Saturday afternoon
and night across Carbon County. Southwest winds will become rather
gusty Sunday afternoon, with windy condiitons from the west and
northwest with the passage of a potent upper trough and surface
front. Rain and snow will develop across Carbon County Sunday
morning, with rain spreading into southeast WY Sunday afternoon
and evening. Temperatures Sunday will once again be quite mild
along and east of the Laramie Range with highs in the 50s and 60s.
Higher elevations out west could measure a few more inches of snow
Sunday night.

.LONG TERM...(Monday through Friday)
Issued at 130 PM MST Fri Feb 17 2017

Monday...Shortwave trough aloft moves from eastern Wyoming in the
morning to central Nebraska by evening with precipitation across our
counties ending from west to east in response to the shortwave
movement. Windy and cooler in the wake of a passing cold front and
with rather strong low and mid level gradients.

Tuesday...Warming trend develops again with strong zonal flow aloft
aiding in a surface lee trough and low level westerly downslope
warming. Enough low and mid level moisture influx for a chance of
afternoon showers across the Snowy and Sierra Madre Ranges, dry
elsewhere.

Wednesday...Next shortwave trough aloft approaches from Idaho and
northern Utah with orographic precipitation advancing across our
western mountains. Again, cooler in the wake of a cold front and
with more cloud cover.

Thursday...Considerably colder in the wake of a passing shortwave
trough aloft and its associated cold front. Looks like enough low
and mid level moisture and dynamics along with upslope for a good
chance for rain and snow.

Friday...Drying out day in the wake of the passing shortwave trough
aloft. With brisk west northwest flow aloft and progged gradients,
looks like a windy day, especially for our wind prone locations such
as Arlington, Vedauwoo and the I-80 Summit and Vedauwoo between
Laramie and Cheyenne. Even colder temperatures with cloud cover and
progged 700 mb temperatures near -12 Celsius.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1021 AM MST Fri Feb 17 2017

Wyoming TAFS...VFR, except for MVFR at Rawlins from 09Z to 15Z.
Wind gusts from 23 to 35 knots through 00Z, then decreasing.

Nebraska TAFS...VFR. Wind gusts from 24 to 36 knots through 01Z,
then decreasing.

&&

.FIRE WEATHER...
Issued at 200 PM MST Fri Feb 17 2017

Minimal fire weather concerns through the weekend with non-critical
fuels. Winds will be breezy through Saturday, increasing Sunday ahead
of a potent upper trough and Pacific front. Lowest afternoon humidities
through the weekend will range between 25 and 35 percent. There will
be chances for rain and snow west of the Laramie Range through Saturday
night, spreading east over and east of the Laramie Range Sunday afternoon
and night. Precipitation amounts will generally be light.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

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


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