385
FXUS65 KCYS 042328
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
528 PM MDT Fri Apr 4 2025

.KEY MESSAGES...

- Cool conditions continue into the first half of the weekend, then
a gradual warmup is expected through next week

- Snow showers dissipate tonight with limited precip potential
thereafter

- Potential for high winds returns Tuesday and Wednesday,
  especially for the prone areas

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 231 PM MDT Fri Apr 4 2025

Synopsis... The axis of an upper trough traversing the Northern
Plains is swinging through the forecast area today. The trough is
bounded by a highly amplified ridge along the West Coast and a
rather broad ridge over the Southeast US. Toward the surface, a
couple lows are centered over the central and southern Rockies with
one accompanying a closed upper low near the Four Corners. To the
north, a burgeoning high pressure is taking over. Extensive cloud
cover and blustery north winds helped keep temperatures well below
normal in the 20s and 30s. Scattered snow showers affected the area,
resulting in minor accumulations primarily on grassy surfaces.

This evening and tonight... The northern Rockies upper trough slides
east with its axis cutting through the Red River Valley. Surface
high pressure drifts south, fully encompassing Wyoming and the Neb
panhandle. With weakening dynamics aloft, dry air advection in the
low levels, and a relaxing pressure gradient, the setup is favorable
for clearing skies and waning winds. Snow shower activity should
primarily be confined to the southern ranges after 00z and mostly
dissipated after 06z. Any additional accumulations should also be
confined to the mountains. One concern through 06z for the eastern
Wyo plains however, is fog. Enough residual near surface moisture
and light winds could prolong patchy fog and mist. Later into the
night, the decreasing cloud cover and lightening winds should allow
for nearly full boundary layer decoupling overnight. Most areas will
likely fall into the teens and the ranges into the single digits.
Trended the min temp forecast toward the NBM mean, which roughly
splits the mid and cool MOS guidance. Temp advection at H7-85 is
fairly weak, only falling about 1-2C in 24 hours, and low level
winds transition to west/downslope. However, will need to watch for
the need to further cool the forecast as the lower quartile of NBM
envelope suggests lower teens.

Tomorrow... Surface high pressure broadens over the Rockies and
northern Plains, continuing to provide generally fair conditions for
the forecast area. The state also falls more under the influence of
the Western US upper ridge, as its axis moves onshore, roughly
lining up with the Cascades. Despite nearly full sun and modest warm
air advection at H7-85 over Wyo and Neb, temperatures only rebound
into the 40s across the board. A few spots in the panhandle may
reach 50F. Forecast values are still about 10 degrees below normal
for this time of year. North/northwest flow resumes in the low and
mid levels, but will luckily mostly behave with perhaps some gusts
to 20 mph. Increased subsidence over the ranges may result in higher
gusts there, but overall the upper flow is rather weak. Internal
wind guidance suggests minimal potential for significant speeds at
the usual spots. Generally clear skies and light winds will allow
for another chilly night, but increasing downslope flow is expected
toward sunrise Sunday.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 231 PM MDT Fri Apr 4 2025

Sunday...Expect a decent warming trend as the flow aloft remains
northerly and 700 mb temperatures rise to near -2 Celsius, yielding
maximum temperatures in the 50s. Limited low and mid level moisture,
thus dry conditions anticipated.

Monday...The warming trend continues as a ridge aloft develops
overhead, with surface lee troughing strengthening. 700 mb
temperatures near 4 Celsius will yield maximum temperatures in the
upper 50s to upper 60s.

Tuesday...West northwest flow aloft strengthens, helping to produce
a windy day, with the wind prone locations possibly near or
exceeding high wind criteria. Continued mild and dry with highs from
the upper 50s to near 70 degrees.

Wednesday...Even windier as the northwest flow aloft strengthens
even further, producing a windy day, with our southeast Wyoming wind
prone locations, such as Arlington, Bordeaux and the I-80 Summit
likely experiencing a high wind event. Continued dry and mild with
maximum temperatures in the 60s.

Thursday...Somewhat less wind expected as a transitory shortwave
ridge aloft builds overhead, helping a surface lee trough to
develop. 700 mb temperatures near 7 Celsius will yield high
temperatures from the mid 60s to near 70 degrees.

Friday...Looks like the warmest day of the week as ridging builds
overhead and with 700 mb temperatures near 10 Celsius, helping to
produce maximum temperatures in the 70s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 520 PM MDT Fri Apr 4 2025

Northwest flow aloft will develop as surface high pressure moves
southward across the terminals.

Wyoming TAFS...For Rawlins and Laramie, ceilings will range from
1500 to 3500 feet until 02Z, then from 5000 to 8000 feet until
12Z, then skies will become clear. Winds will gust to 22 knots
at Rawlins until 02Z.

For Cheyenne, ceilings will improve from 600 to 1500 feet after
03Z, and to 3500 feet after 06Z, before skies become clear after
13Z. Winds will gust to 25 knots until 03Z.

Nebraska TAFS...For Chadron, Alliance and Scottsbluff, ceilings
will range from 2500 to 6000 feet until 03Z, then skies will
become clear. Winds will gust to 28 knots at Chadron and
Alliance until 01Z.

For Sidney, ceilings will improve from 1700 feet to 4000 feet
after 03Z, with skies become clear after 05Z. Winds will gust to
30 knots until 03Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Freezing Fog Advisory until midnight MDT tonight for WYZ116.
NE...None.

&&

$$

SHORT TERM...DS
LONG TERM...RUBIN
AVIATION...RUBIN