017
FXUS65 KCYS 312102
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
Issued by National Weather Service Denver CO
302 PM MDT Mon Aug 31 2026

.KEY MESSAGES...

- Showers and thunderstorms are expected through tonight.
  Strong wind gusts and heavy rainfall possible.

- Drying and warming trend expected going into mid to late week
  with growing potential for elevated fire weather conditions,
  mainly north of Interstate 80.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 256 PM MDT Mon Aug 31 2026

A relatively quiet day across Southeastern Wyoming and the
Nebraska Panhandle is expected ahead of an open wave that is
currently lifting north and east across the Great Basin. Current
mid-level water vapor imagery shows the next influx of
monsoonal moisture associated with this shortwave trough, which
has initiated some impressive convection over Southern Utah,
resulting in localized flash flooding and even some large hail
and damaging winds.

Ahead of the main wave, expect increasing clouds throughout the
day with mostly dry conditions. High temperatures should peak
in the low to mid 80s east of the I-25 corridor, with mainly mid
70s out west where cloud cover onset is expected earlier in the
afternoon. This evening into the overnight hours is when the
strongest (albeit weak) forcing for ascent is expected. Not
anticipating too much in the way of thunderstorm activity as
MLCAPE is progged to be < 100 J/Kg as a result of poor low-level
lapse rates and surface dewpoints in the low to mid 40s, but
cannot rule out a rumble of thunder with any of the heavier
showers. PWAT values overnight remain above the 95th percentile,
however the main surge of monsoonal moisture is temporally
offset from the strongest forcing. High resolution ensemble
guidance has really backed off on QPF, with median values <
0.05 for all of our area.

Showers are expected to gradually decrease in coverage from
southwest to northeast from late morning through early afternoon
on Tuesday as the wave ejects off to the north and east of our
area. High temperatures tomorrow are expected to be slightly
cooler than today, which will ultimately depend on how quickly
showers and clouds depart our area. Can expect westerly winds to
remain breezy, with gusts peaking from 25-30 mph mainly east of
the Laramie Range.

Tuesday night, shortwave mid-level ridging will establish itself
over the Northern Great Plains with a continuing trend of
decreasing cloud cover. Overnight temperatures will remain quite
mild, especially north of the Pine Ridge where 10-25 knot
southerly low-level flow will help to moderate temperatures
thanks to downsloping.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 256 PM MDT Mon Aug 31 2026

Wednesday...Brisk southwest flow aloft prevails. Low and mid
level moisture availability looks scant, thus POPS near zero and
negligible. Based on the low and mid level gradients, it looks
like it will be windy.

Thursday...Similar day to Wednesday with rather strong and dry
southwest flow aloft and decent and deep unidirectional
southwest flow for a windy and dry day.

Friday...The flow backs to south southwest and weakens
somewhat, with minor influx of pseudo monsoonal mid level
moisture, though confidence in shower and thunderstorms
development is negligible thus will keep it dry.

Saturday...Looks like a pseudo moisture tap will emanate up
from the Four Corners with an uptick in PWAT, Precipitable Water
Content, noted, thus expect isolated to scattered afternoon
showers and thunderstorms for our Snowy and Sierra Madre Ranges,
with the activity spreading northeastward and remaining mostly
west of I-25 in the evening.

Sunday...Once again, the rather moist southwest flow will tap
pseudo monsoonal moisture and diurnal heating and orographic
effects will help produce scattered showers and thunderstorms in
the afternoon for locations over and near the Snowy and Sierra
Madre, and northern Laramie Ranges, with the convection
spreading across the remainder of southeast Wyoming and western
Nebraska in the evening.

Monday...Ridging aloft over the Central Plains states bulges
westward across our counties, though with adequate low and mid
level moisture, we still anticipate scattered afternoon and
evening showers and thunderstorms.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 256 PM MDT Mon Aug 31 2026

A weather disturbance aloft will move over the aviation area
tonight and early Tuesday, producing scattered to numerous
showers and some thunderstorms, with the most concentration
south of a Rawlins to Scottsbluff line.

Wyoming TAFS...Confidence is high with scattered showers and a
few thunderstorms this evening, thus will go with prevailing
showers through late evening and early morning. Showers and
thunderstorms will produce wind gusts up to 40 knots, mainly at
the KLAR and KCYS sites. Showers and thunderstorms will end by
late tonight with decreasing cloud cover.

Nebraska TAFS...VFR prevails, with confidence high that showers
will occur at KSNY from 08Z to 12Z, but confidence in showers
elsewhere is less for now thus no mention of showers at this
time. Later updates to the TAFS may need to insert VCSH, or
PROB30s or TEMPOs based on spatial coverage of showers and
thunderstorms.

&&

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

&&

$$

SHORT TERM...WFOCYS
LONG TERM...WFOCYS
AVIATION...WFOCYS