Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 261747
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1047 AM MST Sun Feb 26 2017

.SHORT TERM...(Today through Tuesday)
Issued at 325 AM MST Sun Feb 26 2017

Overnight water vapor loop showed a broad trough across much of
the Lower 48. Short wave troughs were located off the British
Columbia coast, north-central CA, and north-central plains. The
leading edge of arctic air extended from eastern MT across ND and
northwest MN. A 50-60 kt upper jet max was tracking east along
the CO-WY border. This feature along with CAG-CPR H70-85 gradients
around 45 meters was generating strong westerly surface winds
along the I-80 corridor between Rawlins and Cheyenne. Gusts of
60-65 mph observed earlier near Arlington subsided to around 50
mph, with the I-80 summit now peaking near 55 mph. WYDOT webcams
and surface observations indicated reduced visibilities in blowing
and drifting snow. Otherwise, clear skies prevailed with temperatures
in the single digits and teens. Wind chills ranged from 5 to -10
degrees.

Strongest winds early this morning between Cheyenne and Laramie
will gradually subside around daybreak per the CAG-CPR low level
gradients. The gradients increase once again after mid-morning and
continue through early this evening. Still plenty of snow to blow
around across the I-80/I-25 wind prone areas, and extended the
Blowing Snow Advisory until 5 PM MST. A dry air mass will preclude
any precipitation today. It will remain chilly with high temperatures
in the 20s to lower 30s, except teens mountains. Flow aloft backs
from west-northwest to west-southwest during the next 24 hours as
the next Pacific trough digs south across the northwest CONUS and
eventually east through the Intermountain West. Pacific moisture
and increasing upslope flow will lead to better chances for
accumulating snowfall west of the Laramie Range beginning tonight.
Precipitation will then spread east to the I-25 corridor by Monday
afternoon. Models prog a narrow band of light snow stretching
northeast from southeast WY into northwest NE Monday night. The
snow may be heavy at times over the Snowy/Sierra Madres Monday
afternoon and evening, with total accumulations between 6 and 10
inches. A Pacific front will be moving east across the CWA Monday
night. Snow will taper off over the mountains and along the WY-CO
border through the day Tuesday. After a milder Monday with highs
in the 30s to lower 40s, highs Tuesday will be 5-7 degrees cooler,
with breezy west-northwest winds.

.LONG TERM...(Tuesday night through Saturday)
Issued at 245 AM MST Sun Feb 26 2017

Upper trough axis will move east of the CWA Tuesday evening leaving
some snow showers over the the higher mtns into Wed morning. After
that, a mainly dry pattern looks to set up over the region with
warming temperatures as the upper flow gradually turns from
northwesterly Wed and Thursday to westerly by Saturday. Main
concerns will be for periods of gusty winds as short waves move
across the northern Rockys and northern plains and increase the
surface pressure gradient. Strongest winds look to be late Wed and
again early Friday...mainly affecting the wind-prone areas.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1044 AM MST Sun Feb 26 2017

VFR, except for MVFR at Rawlins after 12Z Monday. Wind gusts from
30 to 36 knots through 00Z at Wyoming TAF sites, and 20 to 24
knots at Nebraska TAF sites, then winds decreasing. After 12Z
Monday, wind gusts from 22 to 32 knots at Wyoming TAF sites and
Alliance.

&&

.FIRE WEATHER...
Issued at 245 AM MST Sun Feb 26 2017

Extensive snow pack, cold temperatures, high daytime humidities,
and non-critical fuels will preclude fire weather concerns through
mid-week. Strong and gusty west winds across the wind prone areas
of southeast Wyoming will continue to produce blowing and drifting
snow through late this afternoon. There will be windy periods much
of this week, especially for the normal wind prone areas. There
will be chances for snow early this week, mainly along and west of
the Laramie Range.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 5 PM MST this afternoon for WYZ106-
     110-116-117.

NE...None.
&&

$$

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


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