748
FXUS65 KCYS 231746
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1146 AM MDT Sat Aug 23 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 SUNDAY/...
Issued at 1234 PM MDT Fri Aug 22 2025

What a difference a day makes, a pattern change will continue
through the short term due to northwest flow aloft along with
ridging to our south. These two will dominate the temperatures
and weather pattern across the CWA into the extended period.
Expect below average temps along with daily precipitation
chances into next week. All of what is mentioned above is a
result of a stout upper level low that is slowly trekking
easterly through Canada combined with high pressure locked in
over the southwest.

Most of the CWA is in a Marginal Risk (1 of 5) for sever weather
today due to modest instability and shear along with steep lapse
rates that may allow additional storms to develop this
afternoon and into the evening. One thing that may limit storm
initiation and coverage along with severity is the vast cloud
cover and rain that is currently moving through our CWA, all of
which may inhibit daytime heating. Even though the clouds may
dampen some of the storm severity, we should still see
additional development later this afternoon, especially in
places where the sun breaks out. Hail and wind will be the
primary concerns. 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 for
the next several days due to additional rounds of rainfall and
thunderstorms, however the severe threat will decrease.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 1234 PM MDT Fri Aug 22 2025

Northwesterly flow aloft will remain the primary regime for much of
the week ahead. An upper-level ridge is stationed over the Four
Corners Region and extends up to the north and west into the Pacific
Northwest, leading to ongoing northwesterly flow overhead. A strong
trough is present across southeastern Canada and is strengthening
the jet from about Wyoming northeastward through North Dakota at
250mb Sunday. The strengthened jet will be felt further down in the
atmosphere as slightly breezy conditions develop for Sunday and
Monday. As this trough progresses eastward and deepens across the
eastern CONUS, the upper-level ridge over the Intermountain West
will be unable to advect eastward, leaving it locked in place across
the Four Corners region through much of the week. As a result, the
subsequent northwesterly flow aloft will leave the door open for
multiple disturbances to pass through the flow, giving southeast
Wyoming and western Nebraska daily chances for widely scattered to
widespread precipitation Sunday onwards. Additionally, cloud cover
will be a near permanent feature across the region, aiding in cooler
temperatures and a very "November in the Midwest" feel for much of
southeast Wyoming and western Nebraska. The best chance for breaks
in the cloud cover will be in the afternoon hours, but it looks like
much of the area will remain socked in with clouds every day this
week. Moisture will also be quite high this week with the ample
cloud overhead and monsoonal moisture continuously advecting into the
region due to the high over the Four Corners region. As a result,
almost "muggy" conditions are expected with low clouds and fog a
higher possibility. Thankfully, temperatures will be quite
comfortable, in the 60s and 70s for much of the region Sunday
through Wednesday. Monday is still on track for being the coolest day
in the week, with highs in the mid-60s to mid-70s everywhere.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1142 AM MDT Sat Aug 23 2025

MVFR CIGs at KCYS will break down over the next few hours.
Attention then shifts to thunderstorms, which are most likely
near KLAR and KCYS into the early evening hours. Storms may be
capable of producing strong winds, hail, and IFR VIS in
downpours. While not likely enough to mention in the TAF, these
storms making it to KBFF and KSNY cannot be ruled out.

A reinforcing surface cool front will arrive early Sunday
morning, giving winds more of a northerly component, and
knocking CIGs down at KCYS and possibly KSNY once again.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Dense Fog Advisory until noon MDT today for WYZ116.
NE...None.

&&

$$

SHORT TERM...RZ
LONG TERM...AM
AVIATION...MN