Fort Steele, Wyoming Weather Forecast Discussion

282
FXUS65 KCYS 211136
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
535 AM MDT Sun Sep 21 2025
.KEY MESSAGES...
- Breezy conditions with afternoon rain showers and a few
  thunderstorms are expected this weekend, but overall
  conditions should be fair with a slight warming trend
  expected.
- A cold front and Pacific storm system will bring cooler and
  wetter weather for Monday and Tuesday, before a ridge aloft
  produces drier and warmer weather for Wednesday through
  Saturday.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 330 AM MDT Sun Sep 21 2025
Active and unsettled weather expected across southeast Wyoming
and western Nebraska over the next few days (particularly Monday
and Tuesday) with thunderstorms, locally heavy rainfall, windy
conditions, and even some mountain snowfall. Relatively quiet
weather today though, with all models showing weak ridging aloft
remaining over the Front Range and across the eastern plains.
Models indicate a slow moving subtle shortwave pushing east
across southern Wyoming during the afternoon and evening hours,
which is a bit slower than models were suggesting 24 hours ago.
Expect another round of showers and widely scattered
thunderstorms, but this time further west compared to yesterday
and mainly confined to southeast Wyoming along and west of the
I-25 corridor. Model soundings show stable conditions over far
eastern Wyoming and western Nebraska this afternoon with little
to no CAPE and a very dry airmass between 700 to 500mb, which
will likely mix down to the surface through the afternoon hours
and inhibit convection. Further west, showers will likely
continue off and on through the nighttime hours as the next
Pacific system, and associated upper level jet, begins to move
into western and central Wyoming.
Temperatures on Monday will begin to cool off a bit as the Pacific
cold front moves into the region. 700mb temperatures are
forecast to lower from 10c to 12c on Sunday to -2c to 2c by
late Monday afternoon west of the Laramie Range. This will
likely result in a quick 10 to 15 degree temperature swing over
the region and likely a pretty strong temperature gradient,
which will lead to an increasing pressure gradient ahead of the
Pacific system. Westerly winds are expected to increase in may
even approach High Wind criteria (sustained 40+ mph with gusts
over 58 mph) in the wind prone areas of southeast Wyoming along
portions of I-80 and I-25. Confidence isn`t very high at this
time due to limited 700mb to 500mb flow around 40 knots and
limited boundary layer subsidence near the wind prone locations.
Increased wind gusts over 50 mph at Arlington and Bordeaux
early Monday morning for now. Gusts up to 30 to 35 mph are
expected elsewhere as winds shift into the north. As the upper
level trough digs southeast, expect showers and thunderstorms to
become more widespread through the late afternoon and evening
hours over southeast Wyoming. Increased POP between 60 to 90
percent with heavy rainfall possible with excellent synoptic
lift and decent convective parameters for late September. NAEFS
shows PWAT values above the 90th to 95th percentile for this
time of the year into Monday night.
Not many changes to the previous forecast for Monday night and
Tuesday, with all models continuing to show the upper level
trough diving southeast and stalling near the Wyoming/Colorado
border as it attempts to form a closed low over Colorado. Models
have been trending colder with this system, with forecast
snowlevels now down to 8500 to 9000 feet across southeast
Wyoming. May need a Winter Weather Advisory for the Snowy Range
through Tuesday with snow accumulations approaching 6 inches
over 10,000 feet. Over the lower elevations, high temperatures
will struggle to get out of the low to mid 50s across much of
the area, with some 60s across east central Wyoming and the
northern Nebraska Panhandle...which will be on the northern
fringe of the storm. Most of Tuesday may just be a rainy and
cool day for the I-80 corridor as all models showing moderate to
occasionally heavy rainfall wrapping around the backside of the
Pacific storm system. The biggest uncertainty is rainfall
amounts and snow levels, with some ensemble members showing the
Laramie Valley receiving its first snow of the season. Kept QPF
amounts near the Grand Ensemble 50th percentile for now,
although rainfall amounts may approach an inch and a half if the
75th percentile verifies...which also agrees with most
deterministic models (GFS, ECMWF, Canadian) through Tuesday
afternoon.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY NIGHT/...
Issued at 250 AM MDT Sun Sep 21 2025
Long range models in good agreement, showing the departing
Pacific storm system exiting the Front Range and pushing
eastward into the central Great Plains into Wednesday morning.
It will remain cool than average on Wednesday with highs
generally in the 60s across most of the area...with some low 70s
well north of the I-80 corridor. Will have to watch early
morning low temperatures both Wednesday and Thursday morning as
the more sheltered valleys may have early morning lows around
freezing, which may require Frost and/or Freeze warnings.
Otherwise, most of the area will see lows in the upper 30s to
mid 40s.
All models and ensemble show a ridge of high pressure drifting
into the Intermountain West later in the week and next weekend.
This will result in temperatures climbing above average for this
time of the year along with much drier weather. Models are
showing signs that we`re exiting convective season with hardly
any daytime instability and low CAPE values below 300 j/kg each
day. Kept POP below 10 percent with highs in the 70s for most of
southeast Wyoming, and upper 70s to low 80s for far eastern
Wyoming and western Nebraska.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 535 AM MDT Sun Sep 21 2025
Generally quiet weather expected through 21z TODAY with gusty west
to northwest winds over the southeast Wyoming terminals. Rain
showers and isolated thunder will develop late in the afternoon.
HAZARDS/WEATHER TRENDS: VFR conditions will prevail today and
tonight.  Showers and thunderstorms Sunday afternoon look very
isolated at this time and confined to the southeast Wyoming
terminals. Added VCSH and PROB30 for TS as confidence on timing
increases today. Brief MVFR VIS possible with the heavier showers
and thunderstorms through late this evening.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...TJT
LONG TERM...TJT/SAR
AVIATION...TJT

NWS CYS Office Area Forecast Discussion