Area Forecast Discussion

KEY MESSAGES

- Wind speeds decrease Monday evening under a mostly clear sky. This allows for cooler Tuesday morning lows of 26 to 32 in the far west valleys and basins, while other lower elevation locations generally drop to between 36 and 42.

- Tuesday will be mostly dry, with any isolated late day showers confined to the southern-third of the state.

- Increasing moisture arriving from the southwest Wednesday allows for a better chance of showers and thunderstorms during the afternoon and evening. This trend continues through at least Friday as seasonal temperatures prevail.

DISCUSSION

Issued at 240 AM MDT Mon Sep 14 2026

In last night's discussion, I made a reference to a rather old song from the 80s. Tonight, we are going even further back, to when I was a little kid, the 1970s. And this song, and this band, are very appropriate for today, at least after any showers end shortly after sunset. The song is September, and the band is Earth, Wind and Fire. Meaning on earth (at least in western and central Wyoming), the wind impacts today will be from wind and fire, and it is occurring in September. Just not on the twenty first night, but on the fourteenth day of the month.

The culprits for this are an upper level low now spinning over northern Idaho that will move eastward today. Most of the moisture should be gone by shortly after sunrise, with dry weather returning for the entire area after that. The low will be close enough to keep a decent pressure gradient across the area as well. A jet streak will be moving across the northern portions of the state as well. All this adds up to a rather windy day across most of the area. Most of western and central Wyoming has at least a 2 out of 3 chance of wind gusts over 30 mph today, with a greater than 1 out of 2 chance of gusts over 45 mph in the windier portions of the area. As for the high wind warning, we will leave it up, but it looks borderline. The best chance would be in areas like near Clark and to the west of Cody, where there is around a 1 in 2 chance of wind gusts over 55 mph. There is still the chance of a mountain wave in places like Cody and possibly Dubois or even Lander, but not enough confidence to add to the warning. The strongest wind in the north should be over by around noon, but gusty wind will continue through the day before decreasing tonight as the jet streak moves away and the atmosphere decouples.

The other concern is fire weather. There will certainly be plenty of wind across the area, so that is a slam dunk. The area for low humidity also looks solid, covering areas mainly south of the Owl Creek and Bridger Range as well as Sweetwater County. If there is a mitigating factor, it is that some areas received a decent rain tonight, which should wet fuels at least initially. It has been spotty though, so we will keep it as is. Elsewhere, relative humidity should remain above critical levels. However, elevated fire weather will be likely everywhere as most locations will see humidity under 25 percent this afternoon. As for temperatures, it will be cooler behind the front, with highs fairly close to seasonal normals for the middle of September.

Tuesday looks like a fairly quiet day for most with sunshine mixing with some clouds. Some increased moisture may try to return to far southern Wyoming and could bring a stray shower or thunderstorm. Most activity should hold off until after sunset though. Moisture may push through the southern third of the area to bring a spotty shower or thunderstorm, but most areas will not see one.

The reasoning for the rest of the week remains similar to the past couple of days. And upper level low will move from the Pacific Northwest to the northeast and eventually to the east. There is a bit of more model consensus this morning in taking the low over Montana late in the week rather than into Wyoming. However, there are still some differences in the exact position as well as the speed in which it moves through. Southwest flow will keep some monsoonal moisture moving into the area, as well as bring a return of above normal temperatures. With the increased moisture, there will be a chance of showers and thunderstorms each day from Wednesday through Friday and possibly into Saturday as well. At this point, Thursday and Friday may be the most active days. However, there is still a ton of model spread regarding the placement of timing of the most numerous showers and storms. As a result, we kept largely broad brushed the POPs. At this point, drier air looks to return for the second half of the weekend.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 955 PM MDT Mon Sep 14 2026

Conditions remain VFR through the period. Drier mid-level westerly flow backs to the southwest Tuesday allowing for moisture to increase from that direction. Nothing more than cirrus clouds through the morning, but cumulus will develop across southwest Wyoming, including around KRKS, by mid-afternoon Tuesday. The trend is for isolated showers and thunderstorms in the vicinity of KRKS after 23Z/Tuesday. The moisture deepens toward 06Z/Wednesday and convective coverage increases. At this range, have not included any mention of showers/storms in southwest terminals given hit-and-miss nature of this convection. As for wind, terminals west of the Continental Divide see west to southwest surface wind 10-20kts develop between 20Z-22Z/Tuesday as mixing occurs. These winds diminish just after sunset Tuesday. East of the Divide, an easterly surface wind 6-10kts prevails, with KCPR seeing gusts to 20kts toward 00Z/Wednesday.

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

FIRE WEATHER

Issued at 240 AM MDT Mon Sep 14 2026

Much drier air will move into the area today with any showers ending early. In much of Natrona, Fremont and Sweetwater County, a gusty to strong wind will combine with humidity falling below 15 percent to bring critical fire weather this afternoon. Elsewhere, humidity should remain above critical levels. However, a gusty wind will bring periods of elevated to near critical fire weather, especially in the afternoon.

RIW WATCHES / WARNINGS / ADVISORIES

Freeze Warning from 3 AM to 9 AM MDT Tuesday for WYZ023.