452
FXUS65 KCYS 202043
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
243 PM MDT Thu Aug 20 2026

.KEY MESSAGES...

- Hot and dry conditions will persist through the end of the
  work week.

- Precipitation chances return for the weekend, with the
  possibility of widespread rain on Saturday.

- Daily shower and storm chances return Monday through the end
  of the week with slightly above average temperature expected
  until Thursday.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 239 PM MDT Thu Aug 20 2026

The rest of the afternoon is expected to be quiet as upper-level
ridging strengthens over the Four Corners region. Cannot rule
out a few stray showers moving into the western zones later this
evening from remnant storms that developed in Utah this
afternoon. Best timing for these showers will be between 8 PM
and midnight tonight. Impacts will be minimal, with occasional
brief strong wind gusts possible in and around showers. Most of
the shower activity will be done my midnight, leaving calm
conditions for the rest of the overnight.

Another mostly benign day is in store for Friday as the ridge
continues to strengthen and gradually shifts eastward towards the
Rockies. As a result, high temperatures will be about 3 to 5 degrees
warmer compared to today`s temperatures. The ridge will also do a
good job keeping precipitation chances minimal, however, there are a
few Hi-Res models, namely the HRRR, that show isolated showers and
thunderstorms across southeast Wyoming. There is a decent amount of
instability across the area Friday afternoon with some lift present
from a weak upper-level disturbance moving through the ridge, so
cannot rule out some storms. The main concern with storms, if they
do develop, will be sudden, gusty winds as model soundings show
ample amounts of DCAPE from the dry low-levels. Storm activity
will ease after sunset, leading to a quiet overnight.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 239 PM MDT Thu Aug 20 2026

Saturday...Despite a prominent ridge axis stretching from eastern
Montana southward through eastern Wyoming, there will be adequate
amounts of pseudo monsoonal low and mid level moisture to produce
scattered to numerous showers and scattered thunderstorms in the
afternoon over and near our Northern Laramie, Snowy and Sierra Madre
Ranges in the afternoon, with said convection spreading across the
rest of our County Warning Area in the evening. The convection will
be rather high based though with some decent efficient rain
producers over the mountainous terrain. Somewhat cooler than Friday
with additional cloud cover and precipitation coverage.

Sunday...The ridge aloft is flattened somewhat by shortwaves
traversing in the flow, and with monsoonal moisture transported
further east of our forecast area, coverage of showers and
thunderstorms will be minimized to isolated to widely scattered high
based activity.

Monday...Coverage of afternoon and evening showers and thunderstorms
increases somewhat by an increase in pseudo monsoonal moisture and
lowering 700 mb temperatures providing less convective inhibition,
CIN, compared to Sunday. As is this type of pattern, afternoon
convection will be over and near the mountains due to differential
heating and orographic effects, with the activity spreading across
the rest of the forecast area before dissipation by late evening.
Warmer temperatures compared to the previous day due to less cloud
cover and convective coverage.

Tuesday...Similar pattern synoptically to Monday with minor
perturbations in the flow aloft aiding in lift of pseudo monsoonal
moisture to produce widely scattered to scattered afternoon
convection over and near our Snowy, Sierra Madre and northern
Laramie Ranges, with the activity spreading eastward across the rest
of the forecast area in the evening. Some lowering of mid level
temperatures suggests daytime maximum temperatures will be a little
cooler.

Wednesday...The primary change compared to Tuesday, will be a
reinforcement of the ridge aloft axis over Wyoming, inducing a
return to upslope mechanical lift aiding the areal increase of
showers and thunderstorms, especially east of the mountains and
along the I-25 corridor and eastward. Slight warming trend with 700
mb temperatures near 13 Celsius yielding high temperatures in the
80s.

Thursday...Monsoonal moisture becomes a bit more scant with decent
westerly flow aloft and with warm temperatures aloft producing more
convective inhibition, CIN, to limit development. A slight warming
trend continues based on mid level, 700 mb temperature trends.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1209 PM MDT Thu Aug 20 2026

A dominant ridge aloft will persist through the period from the
Four Corners to western Wyoming and limiting any significant
shower and thunderstorm development due to warm temperatures
aloft and minimal moisture in the low and mid levels. However, a
weak disturbance moving under the ridge axis will produce isolated
to widely scattered showers and thunderstorms affecting Carbon
and Albany Counties of southeast Wyoming from late this afternoon
through this evening.

Wyoming TAFSConfidence is high in VFR through the period. Recent
trends of the HRRR suggest isolated to widely scattered showers
and thunderstorms that may affect the KRWL and KLAR sites from
late afternoon through early evening, though sparsity of said
convection will be too minimal to include in the TAFs. As always,
the strongest showers and thunderstorms will be capable of producing
gusty and erratic winds and gusts and localized turbulence. Clouds
clearing this evening.

Nebraska TAFSVFR expected with high confidence. Expect to see scattered
high based cumulus through early evening, before dissipation.
Winds will be relatively light and variable.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...RUBIN
AVIATION...RUBIN