883
FXUS65 KCYS 021148
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
545 AM MDT Tue Sep 2 2025

.KEY MESSAGES...

- Drier conditions expected through much of this week with a
  warming trend bringing near normal temperatures today through
  Thursday.

- A few isolated showers and thunderstorms possible Tuesday
  afternoon. Mainly near the mountains.

- Cooler temperatures and more unsettled Friday through next
  weekend as a Canadian cold front and a Pacific cold front
  impact the region.


&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 240 AM MDT Tue Sep 2 2025

All models continue to show dry and benign weather for most of
the region as an upper level high near the Four Corners region
lifts northward into Utah and western Wyoming today. Slow
warming trend will continue with weaker north to northwest flow
across the area. Highs will return to the upper 70s to upper
this afternoon..warmest across the lower elevations of far
eastern Wyoming and western Nebraska. Dry conditions will remain
for most of the area today and Tuesday. However, high res CAMs
continue to show a few showers and weak thunderstorms developing
across the mountains and the adjacent plains/high valleys. This
is mainly due to increased surface convergence along the
Laramie Range and slightly better boundary layer instability.
Again, any activity will be brief and likely dissipate by sunset
this evening. Kept POP around 15 to 25 percent from the northern
Laramie Range southward towards the I-80 corridor west of
Cheyenne.

For Wednesday and Thursday, models finally in better agreement
and only show western Nebraska getting clipped by the unusually
strong cold front for this time of the year moving across the
plains and Great Lakes region. Western Nebraska will only take a
glancing blow with limited shallow cooler air. Removed most of
the POP and weather since the surface front will be very shallow
with limited lift. High res guidance shows a few showers
clipping Sioux and Dawes county, so kept a slight chance mention
of rain showers on Wednesday. Still expect a slight cool down
for our area with high temperatures in the mid 70s north of
I-80, and closer to normal along the I-80 corridor. Still expect
Wednesday night and Thursday morning to feel like early autumn
with widespread lows in the to mid to upper 40s for southeastern
Wyoming and western Nebraska behind Wednesday`s cold front.
With the upper level ridge axis nearby, afternoon temperatures
will recover with highs in the upper 70s and mid 80s Thursday
afternoon with another day of dry weather and mostly sunny
skies.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY NIGHT/...
Issued at 255 AM MDT Tue Sep 2 2025

Long range models are trending a little more unsettled for the
weekend and early next week after a Canadian cold front moves
south across the area Thursday night and early Friday. This will
aid in flattening/weakening the upper level ridge across the
western United States and allow Pacific energy to move into the
Intermountain West late Friday through the weekend. We`ll need
to watch what happens in the tropics as a tropical system is
forecast to push north and then northeast into New
Mexico/western Texas on Saturday. Some of this tropical moisture
may advect northward into the Pacific system moving into
Wyoming and Colorado late Saturday and Sunday. Stay tuned.
Otherwise, cooler temperatures will continue this weekend with
increasing chances for showers and thunderstorms. Sunday looks
like the most favorable day for numerous showers and
thunderstorms as the trough axis slowly moves east across the
area. Kept POP between 30 to 60 percent over a bulk of the area.
00z Ensemble spreads are not as high as the last few days with
higher confidence in temps and weather. High temperatures in
the low 70s to low 80s expected...warmest well north of I-80.
Will likely see lows in the 40s for both Friday and Saturday
mornings...with a few locations dropping into the 30s. Ensemble
spreads begin to increase early next week as another strong
ridge develops, but this time along the Front Range and Rocky
Mountain region.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 545 AM MDT Tue Sep 2 2025

Upper level high pressure over Utah and western Wyoming will
dominate the weather over the next few days with mostly dry
conditions and relatively light winds.

HAZARDS/WEATHER TRENDS: VFR conditions will continue with northerly
winds gusting to 20 knots in the afternoon. Some fog has developed
near KAIA early this morning, resulting in fluctuating IFR to MVFR
VIS. Any remaining fog should lift shortly after sunrise.

&&

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

&&

$$

SHORT TERM...TJT
LONG TERM...TJT/CG
AVIATION...TJT