textproduct: Western and Central Wyoming

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.