981
FXUS65 KCYS 241107
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
507 AM MDT Sun Aug 24 2025

.KEY MESSAGES...

- Cool and wet pattern expected for the entirety of the forecast
period, with daily chances for precipitation and highs 5 to 15
degrees below average.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 222 PM MDT Sat Aug 23 2025

A robust upper level low is slowly meandering east across
southern Canada while high pressure remains anchored over the
Four Corners region, pushing a ridge north into our CWA, will be
the two dominate features influencing our weather conditions
here locally through the short term. Northwest flow aloft will
keep temperatures generally below normal while pulses of energy
will swing south from the upper level low over Canada into our
area, bringing daily chances of precipitation to portions of
the CWA at least into next week.

Central portions of the CWA, including Cheyenne, is in a Marginal
Risk (1 of 5) for severe weather this afternoon through the
evening hours. Clouds kept most of the storms at bay through
the morning hours, but visible satellite is showing clearing
occurring which will help destabilize the atmosphere. With
surface dew points in the 50s, steep lapse rates aloft, and
sufficient deep layer shear, all this will help storms initiate
this afternoon. Hail and wind will be the primary concerns with
any thunderstorm development. There is also a concern of
flooding, marginal risk, due to the potential of heavy rainfall
from any thunderstorm activity. The threat of flooding will
continue over the next several days due to additional rounds of
rainfall and thunderstorms, however the severe threat will
continue decrease.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 222 PM MDT Sat Aug 23 2025

Cool and unsettled weather looks likely to dominate the entire week
ahead. The synoptic scale weather pattern will feature an upper
level ridge over the southwest, and a persistent trough over the
Great Lakes region. A surface high lingering over the northern
plains along with ample moisture rotating in over the top of the
ridge will both help keep temperatures on the cool side. High
temperatures will be fairly steady all week, mostly in the 70s.
However, on cloudier days, Cheyenne and Laramie will probably be
stuck in the 60s, while on sunnier days, areas along and north of
the North Platte River Valley should make it into the low to mid
80s. This is a fairly unusual weather pattern to see this time of
year, particularly considering the expected persistence of cool
temperatures and cloud cover across the area each day.

There will be regular chances for precipitation all through the
upcoming forecast period, but the details of any specific day are
somewhat uncertain. On Monday and Tuesday, the axis of the ridge
will be to our west, keeping our area under northwest flow aloft.
Dry air intrusions from the north may move in at various levels of
the atmosphere as shortwave troughs rotate around the broad upper
level trough near the Great Lakes. Weaker forcing for ascent will
generally mean lesser coverage of showers and thunderstorms, but
with perhaps more potential for isolated strong to severe
thunderstorms thanks to decent vertical wind shear and modest
instability. Around the Wednesday time period, the ridge axis is
expected to shift eastward to the Front Range / edge of the High
Plains. this will nudge the influence of dry air off to the north,
while decreasing winds aloft (and thus vertical wind shear), and
increasing mid to upper level moisture. Forcing also looks a little
more potent on Wednesday and Thursday thanks to a modest shortwave
rotating over the top of the ridge. While it is still early with
plenty of time for this to change, Wednesday and Thursday look to
perhaps have greater coverage of showers and thunderstorms, which
may be more of a heavy rainfall setup and a more limited severe
weather potential. Another shortwave around the Friday time period
may keep the active pattern going for another day, but this will
also begin a gradual warming and drying trend, as the ridge aloft
becomes disorganized and meanders slowly to the east.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 506 AM MDT Sun Aug 24 2025

Northwest flow aloft will continue, while another cold front
moves southward across the terminals on Sunday.

Wyoming TAFS...For Rawlins and Laramie, scattered to broken
clouds from 5000 to 12000 feet occur until 00Z, then light rain will
develop after 00Z, reducing visibilities to 4 miles with
ceilings from 2500 to 4000 feet, and areas of fog at Laramie after 06Z,
reducing visibilities to 1 mile and ceilings to 1500 feet.

For Cheyenne, ceilings will range from 800 to 1500 feet, with
light rain and fog developing after 01Z, reducing visibilities
to 3 miles.

Nebraska TAFS...Scattered to broken clouds will range from
5000 to 8000 feet, with ceilings from 1500 to 5000 feet at
Scottsbluff and Sidney after 12Z to 15Z, with light rain and fog
at Sidney after 01Z, reducing visibilities to 4 miles. Fog will occur
at Scottsbluff, Sidney and Alliance after 06Z, reducing visibilities
to 1 to 2 miles and ceilings to 800 to 1500 feet.

&&

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

&&

$$

SHORT TERM...RZ
LONG TERM...MN
AVIATION...RUBIN