769
FXUS65 KCYS 032104
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
304 PM MDT Fri Oct 3 2025

.KEY MESSAGES...

- Widespread precipitation, including rain and thunderstorms,
  expected Saturday as a potent shortwave moves through the
  region.

- Strong winds will be possible in the southeast Wyoming wind
  prones on Sunday. Gusts approaching 50 to 55 mph may be
  possible.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 300 PM MDT Fri Oct 3 2025

A mild and windy, but generally quiet afternoon today will quickly
turn into an active next 36 hours a storm system begins to move into
the area. A few weak upper-level disturbances ahead of the strong
trough and cold front will move into the CWA this evening. These
disturbances will provide enough lift and moisture for scattered
showers and storms to develop late this evening and overnight in
both Carbon and Albany Counties. Cannot rule out a few snowflakes
mixing in with rain in the highest peaks of the Sierra Madre and
Snowy Ranges, however, the CWA will still be locked in relatively
mild south to southwest flow overnight which prevent a full
changeover to snow. Heading into early Saturday morning, coverage of
precipitation will begin to increase.

By Saturday morning, the upper-level trough will begin to push into
western Wyoming, making its way across the state throughout the day.
For much of the day, most of the CWA will be in the warm sector
ahead of the cold front. As the cold front gradually pushes across
the CWA throughout the day, warm, moist air in the warm sector will
be lifted, supporting ample cloud cover and multiple rounds of
precipitation. Instability will also be present in the warm sector,
allowing for thunderstorms to develop. Instability looks marginal at
this time, however, Hi-Res guidance suggests a few linear/bowing
segments developing across the area during the afternoon hours which
could produce a few severe wind gusts and small hail. Coverage of
precipitation will be widespread, with most locations in the CWA
likely to see some rain accumulations. Could start to see rain
transition to snow above 9000 feet in the mountains once the cold
front is through Carbon and Albany Counties during the mid-
afternoon. Most models have the cold front across the CWA by the
evening hours, at which point most of the precipitation will also be
out of the CWA. With the cold front moving through the area,
temperatures will be noticeably colder on Saturday. Highs will
be anywhere from 10 to 20 degrees cooler than Friday, with highs
mostly in the 60s and 70s.

Heading into Saturday night, lingering stratiform precipitation
can be expected in the mountains and in Converse, Niobrara and
northern Carbon and Albany Counties. Wrap around moisture from
the surface low in central Wyoming could support precipitation
in these areas until Sunday morning. Precipitation overnight in
the mountains will also lead to some light snow accumulations in
the Snowy and Sierra Madre Ranges. Flakes are unlikely to make
it down to the surface in the adjacent high valleys, but also
cannot be fully ruled out as overnight lows fall into the 30s.
Besides precipitation, winds will also pick up in the usual
southeast Wyoming wind prones overnight. As the surface low
tracks to the northeast, MSLP gradients over and west of the
Laramie Range will tighten, increasing winds aloft to 50 kts.
There will be decent subsidence to help these winds down to the
surface as well. However, the window for high winds looks brief,
so decided to hold off on issuing anything just yet to wait for
further model guidance.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 300 PM MDT Fri Oct 3 2025

Sunday starts an active beginning of the week as
upper level trough pushes through the Intermountain West. This
trough carries some colder air behind it dropping 700mb heights into
the -2 to -5 range. This will keep in the 50/60`s for Sunday and
Monday. This trough also brings some precipitation chances Sunday
afternoon through Monday morning. The Southeast corner of Wyoming
and the Nebraska Panhandle will remain in the "Warm Sector" of this
trough likely keeping the precipitation rain below 8,500 ft meaning
a chance for snow for our mountain tops. However, during the
overnight period Sunday night into Monday morning temperatures will
drop into the 30`s and low 40`s likely creating some frost in the
early morning Monday and possibly Tuesday morning as well. Due to
the passage of this trough, the pressure gradient will tighten
across the forecast area creating gusty conditions Sunday into
Monday afternoon as well. Starting Tuesday, another ridge slowly
starts to build over the Intermountain West. There is a weak
shortwave that passes through the Intermountain West, but the
associated precipitation chances looks to be isolated to the
mountains Tuesday afternoon and evening. However, temperatures do
start to gradually warm up returning to the 60`s and 70`s by
Wednesday afternoon.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1143 AM MDT Fri Oct 3 2025

VFR conditions are expected through the day today with breezy
conditions at most terminals. Increasing clouds and precipitation
chances will be possible later this evening for areas west of the
Laramie Range. Low CIGs should hold off overnight, although cannot
rule out any visibility reductions due to rain.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...MM
AVIATION...SF