634
FXUS65 KCYS 261931
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
131 PM MDT Sat Sep 26 2026

.KEY MESSAGES...

- Warmer this weekend with temperatures around 5 to 10 degrees
  above normal. Chance for Thunderstorms on Sunday as the next
  Pacific storm system moves onshore.

- A strong Pacific storm system will bring scattered showers and
  storms along with seasonably cool temperatures for the start
  to middle of next week, with a slow warming trend into the
  later part of the week.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 115 PM MDT Sat Sep 26 2026

Conditions remain mostly quiet today under drier air across the
CWA. That being said, there is some meager moisture present
along with upslope flow across the higher terrain of the
region, and high resolution guidance does try to produce some
sort of, albeit weak, echoes for the area. A small thunderstorm
did form just south of the Wyoming border and quickly fell
apart, and that`s what the expectation will be moving into the
rest of the afternoon and evening as we may see some weak
precipitation pop up and then fall apart as quickly as it came,
mostly for areas along and west of I-25. Otherwise we continue
to see some breezy conditions but nothing too unusual for this
region under mostly fair skies.

On Sunday expect a similar setup in regards to temperatures as
highs once again sit around 7 to 10 degrees above normal with
widespread 70`s to 80`s. But as flow turns more southwesterly
and brings low and mid-level moisture back to the region, we`ll
begin to see an increase in precipitation chances once again. We
should see activity start to form off of the high terrain
beginning during the mid to late afternoon timeframe and
continue into the evening and overnight hours. While stronger
and more favorable conditions for enhanced storms will sit just
off to our east, a pocket of modest instability in the realm of
500-1000 J/kg alongside bulk shear values in the 30-40 knot
range should be present across primarily the Nebraska Panhandle,
and so as convection develops and propagates eastwards we may
see a stronger storm or two for the area. Initial lapse rates
will also be quite favorable, but with storms forming a bit on
the later side it`s likely they won`t be able to take advantage
of this during the evening. With PWAT values also on the rise
thanks to this influx of moisture, peaking at around 0.75-1 inch
for the day, some of this activity could produce very localized
heavy rainfall, but storms are expected to remain isolated to
scattered in nature and therefore a widespread precipitation
event is not likely for the area. Chances may be better moving
into the long term, but even that may be lessening with the
newest model runs.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 115 PM MDT Sat Sep 26 2026

Unsettled weather will continue into the early part of the week
ahead, but it is widespread beneficial rainfall is looking less
likely. A split trough approaches the area on Monday, with the
northern split passing to our north, and the southern split will be
abandoned over the southwest to eventually absorb abundant tropical
moisture associated with the remnants of Hurricane Polo. While
precipitable water will be well above average Monday through early
Wednesday, pushing around the 90th to 99th percentile of
climatology, forcing for ascent looks weak at best, and instability
remains unimpressive. The official forecast maintains modest PoPs
(mostly 20 to 50%) through Monday and into Tuesday morning, as we
can expect to see at least a few showers and storms around, but odds
of significant rainfall are slim. Probabilities for total
precipitation (through Tuesday) over 0.1" are lowest between I-25
and the WY/NE state-line, running around 20 to 50% here. Western
Nebraska and the higher terrain of southern Wyoming both have higher
odds, between about 50 and 80%. That being said, expect rainfall to
be spotty, though the abundant atmospheric moisture will support the
potential for highly localized heavy rainfall. A cool front moving
through the area will knock down temperatures for Monday, with
Tuesday looking like the coolest day.

For the middle of the week, the most likely scenario puts our area
just outside of the region of precipitation associated with a soggy
closed upper level low to our south. Ensembles are still all over
the place in terms of the location of this low pressure system as it
ejects eastward into the plains Wednesday into Thursday, but only
the far northern end of the envelope of solutions (10 to 20%
probability) would bring any impact to our area. The vast majority
of ensemble members keep all rainfall with this system to our south,
but it is still worth a mention as a shift north would lead to a
vastly different outcome than currently shown in the official
forecast for Wednesday and Thursday. Expect temperatures to warm up
through the latter half of the week, with highs peaking above
seasonal averages on Friday.

Another low-confidence storm system is showing up in a handful of
ensemble members around next weekend. This will be another Pacific
trough moving from the northwest. In about 20% of ensembles, this
system is strong enough to knock temperatures enough to support a
widespread freeze Sunday morning along with a quick shot of rain and
snow showers to the area. However, the other ~80% have light
showers and a modest cool down, with overall minimal impacts.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1120 AM MDT Sat Sep 26 2026

VFR conditions expected for the forecast period. Mid-level cloud
cover will increase this afternoon, especially in Wyoming as
west to northwest winds gradually weaken. Winds will be variable
at times late this afternoon into the early evening, especially
in Wyoming where some high based showers will be affecting the
wind. Not much more than a few sprinkles is anticipated. Winds
will be generally light overnight before picking up again late
morning Sunday.

&&

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

&&

$$

SHORT TERM...CG
LONG TERM...MN
AVIATION...MN