Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 262156
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
256 PM MST Sun Feb 26 2017

.UPDATE...
Issued at 253 PM MST Sun Feb 26 2017

Went ahead and cancelled the Blowing Snow Advisory early. Looking
at WYDOT Webcams, snow looks to be settled pretty good as it has
been blowing around pretty good earlier this morning. Still
getting fairly strong winds, but snow seems to have possibly
crusted or has found its permanent drifted area. Will handle the
winds with an SPS.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 300 PM MST Sun Feb 26 2017

Active weather in the short term with winter headlines and winds
the main forecast concerns.

Currently...Strong winds continue this afternoon in the wind prone
areas of southeast Wyoming. Did have a few gusts around 58MPH this
morning out by Arlington with low 50s over the Summit and mid 40s
up by Arlington. Looking at area webcams, its looking like the
blowing snow may have settled down from this morning and may be
able to end the Blowing Snow Advisory earlier than expected. WIll
continue to monitor for another hour or so and then decide.

Next Pacific storm system moving into the PACNW this afternoon.
Cold front over southern Montana likely at least partially
responsible for the strong winds today. A 1020 surface high
situated over southwestern Wyoming this afternoon aiding in mostly
sunny skies over the area.

This next storm system begins to impact the area Monday. All
models in good agreement with the front moving into Carbon County
Monday afternoon. NAM, SREF, EC, GFS all agree on timing and
location of a moderate QPF area moving into Carbon County tomorrow
afternoon. NAM the most bullish with over .5 inches QPF, but other
models not too far behind. Looks like most of Carbon County will
be under this precip for a 12-15 hour time span before the front
moves into Colorado. At the same time, GFS 700mb winds ahead of
the front up near 40kts from the southwest that shift northwest at
35kts behind the front.

Did disagree with the WPC snow amounts they are forecasting and
did coordinate with them on my concerns. All this precip should
fall as snow as we are only forecasting highs out at Rawlins of
28 tomorrow. So I am getting snow amounts of 3+ inches from
Rawlins south to Saratoga with highest amounts outside the
mountains in the foothills. Sierra Madre Range stands best chance
at seeing 12+ inches while the Snowy Range may get shadowed by the
Sierra Madre. This leads to my headlines.

Went with a Winter Storm Warning for the Sierra Madre Range and an
Advisory for the Snowy Range. Windy conditions out by Rawlins and
along I-80 near Arlington could produce significant impacts. So
issued a Winter Storm Watch for the areas surrounding the
mountains for Monday afternoon through Tuesday morning. There are
impacts at Arlington with no snow falling, so you add 3-5 inches
with 40 MPH winds similar to the past couple days, there certainly
looks to be major impacts out there.

.LONG TERM...(Wednesday through Sunday)
Issued at 300 PM MST Sun Feb 26 2017

Wednesday...Aside from a few mountain snow showers, the first day of
March looks to start out dry. Temperatures will be cooler than
normal considering the snowpack and progged 700 mb temperatures near
-10 Celsius. Windy day, with near high wind criteria winds likely at
our wind prone locations such as Arlington, Bordeaux and Vedauwoo
over the I-80 Summit between Laramie and Cheyenne.

Thursday...Although flow aloft remains from the northwest, heights
aloft rise helping the temperatures to rise a few degrees at most
locations. Continued windy based on progged low and mid level
gradients, though likely not as windy as Wednesday as mid level
winds decrease slightly. Lack of low and mid level moisture suggests
a dry day.

Friday...As happens quite often, with the flow aloft backing to
westerly, surface lee troughing becomes better established and the
atmosphere will warm substantially as a result with high
temperatures warming to above normal readings.

Saturday...Warming trend continues in earnest under zonal flow and a
moderating airmass sending high temperatures above normal for early
March. Continued dry with absence of significant low and mid
level moisture. Another quite windy day per progged low and mid
level gradients.

Sunday...Somewhat cooler temperatures as a progressive and low
amplitude shortwave trough aloft and cold front progress west to
east across our forecast area. If shortwave timing is correct, we
may see enough low and mid level moisture to produce a chance of
rain or snow along and west of a Douglas to Rawlins line.

&&

.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 300 PM 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 from 2 PM Monday to 5 AM MST Tuesday for
     WYZ114.

     Winter Storm Watch from Monday afternoon through late Monday
     night for WYZ109>111-113.

     Winter Storm Warning from 2 PM Monday to 5 AM MST Tuesday for
     WYZ112.

NE...None.
&&

$$

UPDATE...GCC
SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...GCC


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