textproduct: Western and Central Wyoming

KEY MESSAGES

- A mainly dry and seasonable day today. A few showers are possible in southern Wyoming this evening and tonight.

- Increasing monsoonal moisture increases the chance of showers starting on Wednesday, with Thursday and Friday looking like the most active days.

- Temperatures will remain near to above normal through most of the week, with a cool down likely for the weekend.

DISCUSSION

Issued at 149 AM MDT Tue Sep 15 2026

The last two nights I used music to describe the weather of the day. So, why not make it three days in a row. Lets step back another decade today, to the 60s. And let us also change music genres again, this time to country. And this has to with a pattern that you would expect more during the middle of summer, not a week from the start of autumn. The song is by the late, great Johnny Cash, Ring Of Fire. Basically, a strong ridge sets up in the southern United States and moisture rides along the northern edge of it.

There continues to be an strong ridge over the southeastern and south central United States, bring more record high temperatures. For us in Wyoming, we will be close to the top of the ridge, with an increasing chance of showers. For today and most of tomorrow, the bulk of the moisture looks to remain to the south of Wyoming. Just enough moisture will creep northward late today and especially tonight to bring some showers to the southern third of the state. But these still look fairly isolated and even here most locations should not see one (less than a 1 out of 4 chance). Moisture will try to creep further north on Wednesday but even on this day the bulk will remain south of the border with only isolated activity. As for temperatures, today looks fairly close to normal. With southerly flow increasing Wednesday, temperatures look warmer with highs rising to around 80 in some of the warmer spots.

Chances of showers should increase beginning Wednesday night and especially into Thursday and Friday. The ridge over the southeastern United States with retrograde toward the southern plains. At the same time, low pressure over the Pacific Northwest will begin to get pushed eastward. moving toward Idaho by Thursday night. This will push the plume of monsoonal moisture further north and west and into the Cowboy State. Precipitable water values could be rather high. The GFS has values approaching an inch, which is approaching 200 percent of normal Wednesday night and Thursday. This model does tend to overcook this somewhat, so reality may be closer to 150 percent of normal. Nevertheless, the chance of showers and storms will increase. Model guidance continues to have disagreements in the placement of the most numerous showers though. So, we have higher confidence in Thursday and Friday being the two more active days, but placement of the most numerous showers and precipitation amounts remains uncertain. Temperatures will remain somewhat above normal, although with more cloud cover a bit cooler than on Wednesday. And like most monsoonal events, all areas will have a chance of a shower or storm, but not everyone will see one.

There is more uncertainty for the weekend. There is still a decent model spread on how fast the low will exit the area. Most guidance now takes the low north of the area across Montana. With flow turning northwestward, Saturday looks like a cooler day across the area. How fast the low moves will determine the extent of any precipitation though since it will be of the wrap around variety. Most guidance favors northern Wyoming given the position of the low, with lesser chances further south. Sunday looks somewhat drier although a few areas may still see a few showers around. Ridging should build back over the area to start next week, bring a return to dry and seasonable weather.

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.

RIW WATCHES/WARNINGS/ADVISORIES

Freeze Warning until 9 AM MDT this morning for WYZ023.