Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 251729
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1029 AM MST Sat Feb 25 2017

.SHORT TERM...(Today through Monday)
Issued at 315 AM MST Sat Feb 25 2017

Overnight water vapor loop showed a deep upper trough over the MS
River valley, with a band of convection progressing across the
eastern Great Lakes south into the TN valley. A near zonal flow
aloft prevailed from the Great plains across the Intermountain West.
A weak surface trough extended north-south across the high plains.
Winds along and west of the Laramie Range were gusting to 40 mph,
with lighter winds to the east. Skies were mostly clear areawide.
Freezing fog developed along the North Platte River valley late
Friday evening. The fog has been dense at times at Alliance,
Douglas and Torrington. Temperatures were quite cold, ranging from
-7 at Alliance to 18 at Bordeaux. Wind chills were in the single
digits and teens below zero.

Concern today after the morning fog dissipates will be gusty winds
and potential for blowing snow across portions of southeast Wyoming.
700mb CAG-CPR height gradients increase to 40-50 meters after 15Z
and continue through early this evening. 700-750mb winds ramp up
to 45 kt for wind prone areas including Arlington, Bordeaux and
southern Laramie Range with the passage of a shortwave trough.
Westerly winds gusting to 50 mph will create areas of blowing snow
through this afternoon for wind prone areas. Visibilities will be
reduced to less than a mile at times with slick roads. Winter
Weather Advisory for blowing snow remains in effect until 5 PM
this afternoon. Westerly upslope winds and lingering moisture will
produce orographic snowfall over the Snowy/Sierra Madres today
and tonight. Accumulations will range from 2-4 inches. Fresh snow
pack will keep high temperatures cooler than MOS guidance, with
teens and 20s. Lows tonight will range from -5 to 10 degrees.
Patchy late night fog will be possible again along the North
Platte River valley.

Sunday will be similar to today with a tight low level gradient
and 700-750mb winds near 45 kt. Expect gusty west-southwest winds
to 40-50 mph for wind prone areas. Blowing snow may be a concern
again Sunday. It will be dry areawide Sunday with high temperatures
in the 20s-around 30, except teens mountains/high valleys.

Winds aloft back to southwest early Monday as next Pacific trough
tracks southeast into the Intermountain West. Increasing moisture
and upslope flow will bring good chances for accumulating snow to
areas west of the Laramie Range. The Snowy/Sierra Madres could
measure up to 5 inches by late Monday afternoon, with a few inches
for the valleys. Southwest winds will gust to 40 mph along and
west of the Laramie Range. Monday will be milder with highs mostly
in the 20s and 30s.

.LONG TERM...(Monday night through Friday)
Issued at 215 AM MST Sat Feb 25 2017

Upper shortwave will pass by the area Monday night and bring some
light snow or snow showers to mainly southern parts of the CWA.
Snow showers should persist over the higher mtns Tuesday into
Tuesday evening as the main upper trough moves across the region.
A relatively minor cool front will also swing past early Tuesday
keeping temperatures below average through Wed. Gradual warmup
then seen for Thursday and Friday with mainly dry conditions in
northwesterly upper flow. It looks like it will get increasingly
windy especially by Friday morning as lee troughing deepens over
the high plains and sharpens the surface pressure gradient.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1026 AM MST Sat Feb 25 2017

Wyoming TAFS...VFR prevails. Wind gusts 30 to 35 knots through
00Z, then winds decreasing. Wind gusts 25 to 28 knots after 15Z
Sunday.

Nebraska TAFS...VFR prevails. Wind gusts 20 to 28 knots through
00Z, then winds decreasing. Wind gusts 20 to 25 knots after 15Z
Sunday.

&&

.FIRE WEATHER...
Issued at 215 AM MST Sat Feb 25 2017

An extensive snow pack, cold temperatures and high humidities will
preclude fire weather concerns through early next week. Gusty
westerly winds today will produce areas of blowing snow for wind
prone areas of southeast Wyoming.

&&

.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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