Granite Canon, Wyoming Weather Forecast Discussion

421
FXUS65 KCYS 301129
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
529 AM MDT Tue Sep 30 2025
.KEY MESSAGES...
- Mild to warm temperatures will continue through Friday, before
  a potent weather disturbance aloft and its associated cold
  front bring cooler and wetter weather for Saturday through
  Monday.
&&
.SHORT TERM /THROUGH THURSDAY/...
Issued at 315 AM MDT Tue Sep 30 2025
Today...Southwest flow aloft continues, with a slight warming trend
as 700 mb temperatures near 9 Celsius yield maximum temperatures in
the 70s west of I-25, with upper 70s to mid 80s east of I-25.
Perhaps enough mid level moisture for isolated afternoon and evening
showers and thunderstorms to the south of a Rawlins to Alliance line.
Wednesday...Drier zonal flow aloft develops, producing a dry day,
with temperatures about the same as Tuesday.
Thursday...A warming trend develops again as the flow aloft turns
southwest, with 700 mb temperatures near 10 Celsius yielding maximum
temperatures in the lower to mid 70s west of I-25, with 80s east of
I-25.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 315 AM MDT Tue Sep 30 2025
Friday...Southwest flow aloft strengthens in advance of the potent
shortwave trough aloft over eastern Utah. With a slight increase in
cloud cover, high temperatures will be slightly cooler. Looks like
adequate low and mid level moisture to spark isolated to widely
scattered afternoon and evening showers.
Saturday...The progressive shortwave trough aloft moves to eastern
Wyoming in the afternoon, producing scattered showers and isolated
thunderstorms, in addition to cooler temperatures in the wake of a
cold frontal passage. Low and mid level gradients suggest a windy
day for much of the forecast area.
Sunday...Strong southwest flow aloft prevails over cool surface high
pressure producing low level upslope and extensive cloud cover. 700
mb temperatures near 0 Celsius will yield cool daytime high
temperatures from the mid 50s to mid 60s. The lift produced by low
level upslope and a weather disturbance aloft will help generate
scattered showers and isolated thunderstorms in the afternoon and
evening.
Monday...Cool surface high pressure across the western high plains
will help keep cool low level upslope in place with maximum
temperatures only in the mid 50s to lower 60s. Adequate low and mid
level moisture will help produce isolated to widely scattered
afternoon and evening showers.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 525 AM MDT Tue Sep 30 2025
Southwest flow aloft will continue. Skies will be mostly clear
this morning, with scattered to broken clouds from 8000 to
12000 feet this afternoon and tonight. Winds will gust to
30 knots at all terminals except Scottsbluff from 17Z to 01Z,
and to 30 knots at Chadron and Alliance after 04Z.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...RUBIN
LONG TERM...RUBIN
AVIATION...RUBIN

NWS CYS Office Area Forecast Discussion