textproduct: Western and Central Wyoming

KEY MESSAGES

- Trending drier today with widespread near critical fire weather across much of the area this afternoon with lower humidity as low as 15 to 25 percent and gusty southwest winds up to 30 to 45 mph.

- Thursday still looks to be the day of most concern with the lowest humidity as low as 10 to 15 percent. The fire weather watch has been upgraded as a result to red flag warnings. Further near critical fire weather is possible on Friday into Saturday.

- Monsoonal moisture returns later this weekend into early next week with an increased chance of showers and thunderstorms, but details on placement of the most numerous showers remains uncertain.

UPDATE

Issued at 1145 AM MDT Wed Sep 2 2026

Mid-day convection has kicked off across the Winds and northern Sweetwater County, and HiRes models did not do well on initiationfor both timing and location. The NAMNest has come around to it finally, with HRRR shortly behind as per usual. Some activity to the west as well and will continue through the afternoon and early evening hours. Not much in the way of instability for anything stronger to severe, but gusty outflows over 40 mph and frequent lightning the main hazards. These will wane towards sunset with nothing of note overnight into tomorrow.

Otherwise, fire weather watches for Thursday afternoon and early evening have been upgraded to red flag warnings with good confidence on low humidity values and gusty winds. East of the Divide will be the best areas of concern in regards to fire weather. Friday and Saturday afternoons will not be quite as windy but still elevated to near critical conditions to be re- evaluated after Thursday if any products need to be issued. The system for late Sunday and into next week still uncertain at this time, but timing continues to be pushed back a little each model run. Stay tuned for updates in the coming days.

DISCUSSION

Issued at 222 AM MDT Wed Sep 2 2026

My favorite thing in the whole world (note my sarcasm) is continuing this morning, nocturnal monsoonal convection, with the models doing their usual great job with it (more sarcasm). They are gradually weakening though. A couple of showers may linger into the morning but this would be isolated. The trend today will be for convection chances to trend downward through the day as much drier air punches in from the north and west. There may be enough moisture for a stray shower or thunderstorm across southern Wyoming this afternoon, but the chance is small, generally less than 1 out of 5. We have some slight POPs in this area to cover for this. However, our attention will turn to something else.

And that is fire weather. The pattern will be the same for the next three days or so. The set up is the same as was discussed yesterday Wyoming will be roughly the midpoint between an upper level low off the Pacific Northwest coast and riding over the southeastern United States. As a result we will have a fast flow over the area. The 700 millibar winds are fairly strong for this time of year as well, generally peaking at 35 to 40 knots. Much of the eastern half of the area has at least a 1 in 2 chance of wind gusts past 30 mph as a result. The limiting factor for fire weather today is humidity. Mean relative humidity among the ensemble members is generally above 15 percent, although it does get close in Johnson County where it drops to around 17 percent. So, for now, we will not issue any fire weather highlights. However, elevated to near critical fire weather is likely today for most locations East of the Divide. Temperatures will be rather warm as well, generally about 5 degrees above normal with the warmer spots like the eastern Bighorn Basin making a run at 90 degrees.

Thursday looks like most concerning day for fire weather. This will be the driest day across the area, with humidity generally running around 5 percent lower than on Wednesday. Wind will be a bit lighter though, generally be around 5 mph. However, there is still a greater than 1 in 2 chance of wind gusts past 25 mph across much of the area, With this, we will issue a fire weather watch across most of the area East of the Divide as well as most of southern Wyoming, although humidity will be a bit more borderline in this vicinity. The chance of showers looks to be close to zero as well, with the only place with a chance the far northwest where the chance is less than 1 in 5 and largely in the morning. On Friday, we will still have the wind. However, humidity looks somewhat higher, especially across southern Wyoming. We may need additional fire weather highlights on this day but will hold off for now since things look more borderline.

As we head into the weekend, humidity will continue to creep up and wind should decrease somewhat on Saturday, and this should be the end of the critical fire weather. The next question is about the next surge of monsoonal moisture and any possible interaction with a tropical cyclone in the western Pacific. Models trends are still slower, with most holding off until Sunday now, and continuing into Monday. Most guidance also takes the tropical cyclone further off of the coast, limiting the moisture somewhat. However, some guidance still gives over an inch of precipitable water for Sunday and Monday. Details the placement of the most numerous showers are still uncertain given it is still several days out though. Precipitable waters are still expected to climb to over an inch though, so some locally heavy rain is still possible. As for temperatures, with the ridge still expected to retrograde closer to the area, expect above somewhat above normal temperatures to continue into the weekend.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1137 AM MDT Wed Sep 2 2026

Isolated to scattered showers and thunderstorms are expected initiate off the higher terrain and move northeast this afternoon. There is higher confidence (30 percent) that KCOD, KCPR, and KRKS will see a shower or thunderstorm Wednesday afternoon. All other terminals have a 10 to 20 percent chance of seeing convection at or around the terminal. The main impact in any shower or thunderstorm will be gusty 35 to 50kt winds and brief instances of lower visibilities. Convection chances diminish quickly after sunset, except at KCPR where light rain is possible overnight. Outside of any showers or thunderstorms, gusty 25 to 35 kt winds are forecast through this evening before diminishing between 01Z and 05Z Thursday. Anticipate relatively light winds overnight before increasing and becoming gusty late Thursday morning.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts.

FIRE WEATHER

Issued at 222 AM MDT Wed Sep 2 2026

Widespread elevated to near critical fire weather is expected today. There is a greater than 60 percent chance of wind gusts past 30 mph across much of the area. Relative humidity should remain above critical levels for the most should remain above 15 percent, although brief periods of critical fire weather are possible in some locations this afternoon. The day of greatest concern continues to be Thursday, when humidity will be the lowest. Further elevated to possible critical fire weather is possible Friday before conditions improve this weekend.

RIW WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from noon to 9 PM MDT Thursday for WYZ275>283- 285>289-300.