298
FXUS65 KCYS 050545
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1145 PM MDT Fri Sep 4 2026

.KEY MESSAGES...

- Warming and drying trend expected through the end of the week.

- Precipitation chances return for the beginning of next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 114 PM MDT Fri Sep 4 2026

Current conditions are warm and dry area wide with mostly clear
skies for most locations. Along mountain ranges there are some
cumulus cloud development coinciding with increased insolation
this afternoon. A few showers or storms could develop from these
clouds in the later afternoon and evening hours along I-25 from
Cheyenne to Douglas. The supporting mechanism for this activity
would be a weak shortwave passage and monsoonal moisture aloft.
PWAT values between 0.75 to 1.5 inch despite the low near
surface moisture would additionally fuel showers/storms. CAPE
values below 500 J/kg should limit the intensity of the storms
moving off the mountains. Further east is the western extent of
better moisture and instability. It is removed from the better
force for ascent with the weak shortwave, so it is uncertain if
storms will fire here. The best signal is for a storm to
perhaps develop near Chadron and move east out of our area in
quick order. Again this is of low confidence. Highs this
afternoon will reach the low to mid 90s east of I-25 and low to
mid 80s for points west. Some elevated fire weather conditions
are possible, especially in Carbon, Converse, and Niobrara
Counties given the low humidity and breezy conditions.

Tonight any lingering showers or storms along I-25 should
dissipate by about 11 PM with the loss of daytime heating and
our shortwave departing to the north. Lows in the 50s and low
60s are anticipated. Better moisture will be in place Saturday
as the upper level trough over the Pacific Northwest sends yet
another shortwave over the region. Storm coverage is expected to
be greater as a result. Uncapped CAPE values generally around
500-1500 J/kg and shear 25-30 knots would promote clusters of
multicellular storms. An isolated occurrence of severe caliber
winds could manifest from any consolidated cold pools underneath
these clusters. DCAPE values between 1000-1500 J/kg are
certainly high enough to support this risk, though some low
level dry air entrainment would hinder this somewhat. The SPC
has a marginal risk for severe weather primarily for our
Nebraska Panhandle areas. PWAT values between 1.0 and 1.5 inches
and slow/training storms would make flooding an isolated
concern. Highs in the afternoon are very similar to those seen
Friday, generally in the 90s east of I-25 and 80s west.
Overnight increasing cloud coverage and shower activity starts
spilling over from the Pacific system moving closer to the area from
the west.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 532 AM MDT Fri Sep 4 2026

Sunday, the low over the Pacific Northwest starts to push
against our upper level ridge as it tries to push further into
the interior of western United States. When this occurs more of
the monsoonal moisture will feed over our region priming the
Intermountain west for more storm activity. The storm coverage
will slowly increase as well as more moisture feeds into the
region. The system will inch towards the Intermountain West and
start to flatten our ridge.

The trend of showers and thunderstorms continue through Monday
and Tuesday as the stubborn trough to the northwest finally
ejects into the central plains. While moisture will remain
high, a lobe of drier air associated with a ridge to the east
may be pulled in ahead of the trough which would reduce rain
potential. However, since the trough is ejecting it is possible
that cyclogenesis occurs nearby increasing the severe weather
potential. Some machine learning models are highlighting an
uptick in that potential for the Nebraska Panhandle area.
The details of how this unfolds will be ironed out as we get
closer.

The remainder of the long term is in a drying trend. The
ridge noses in. This would not completely shut down storm
activity.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1145 PM MDT Fri Sep 4 2026

Overall, still expecting a quiet overnight at all terminals with
mostly clear skies and light winds. Newer Hi-Res guidance has begun
to hint at potentially some showers developing earlier in the
morning around KCYS and some of the Nebraska panhandle terminals.
However, confidence in this is low, so kept it out of the TAFs for
now. A better chance for showers and thunderstorms is expected
during the afternoon hours on Saturday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...RV
LONG TERM...MM
AVIATION...SF