Greybull, Wyoming Weather Forecast Discussion

654
FXUS65 KRIW 181031
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
431 AM MDT Thu Sep 18 2025
.KEY MESSAGES...
- Mainly dry and warmer conditions today through Saturday.
- A cold front will move across the area Sunday and Monday,
  bringing some showers, gusty wind and a brief drop in
  temperatures.
- Warm and dry weather returns for Tuesday and much of next
  week.
&&
.DISCUSSION...
Issued at 123 AM MDT Thu Sep 18 2025
We are now entering a quieter period of weather as the upper
level low that brought the showers earlier this week has now
moved into the Plains states. Ridging will build over Wyoming
and bring a nice early autumn day for the most of the area,
with comfortably warm temperatures and light wind. The one small
fly in the ointment will be a weak shortwave dropping across
far eastern portions of our area. There may be just enough
instability and moisture for an isolated shower or thunderstorm
this evening in Johnson County. The chance is small with a
capital S though (less than 1 out of 6). Any threat of this
should end shortly after midnight.
Friday looks like a nice late summer day with temperatures averaging
around 10 degrees above normal. Saturday also looks like a nice day
across most of the area as well with warm temperatures and a few
more clouds. Some mid level moisture may try to approach
southwestern Wyoming and bring a late day or evening shower or
thunderstorm though. However, the chance once again is small
(less than 1 out of 5).
The next quandary in the forecast is what happens Sunday into Monday
with an approaching cold front. The latest model trend has moved
further south and a bit stronger with the front, and an upper level
low possibly developing as it passes through Wyoming. Coverage of
convection has increased with this latest model run as a
result. There has been a large lack of consistency with the
guidance with this system though, with models flip flopping more
than a fish out of water. My confidence in the passage with
some gusty wind and cooler temperatures for early next week is
high, but confidence of the details on placement or coverage of
any precipitation remains very low. Some more model consistency
could improve this though. With the frontal passage, there could
be some elevated fire weather ahead of it in the southwest
flow, pre-frontal areas Sunday, mainly Rock Springs to Casper.
Monday will be a cooler day in the wake of the front, with
temperatures near to a few degrees below normal.
Ridging should then build back northward for Tuesday and into
the middle of next week, bringing dry conditions and above
normal, but not hot temperatures, through Thursday.
&&
.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 430 AM MDT Thu Sep 18 2025
SKC skies through much of the TAF period, with increasing high
clouds across much of the area after 03Z. Winds will remain
light, 10 kt or less.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence
forecasts.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Hattings
AVIATION...LaVoie

NWS RIW Office Area Forecast Discussion