textproduct: Western and Central Wyoming

KEY MESSAGES

- Sunday remains unseasonably hot with widespread high temperatures in the 90s and lower 100s for many lower elevation locations. More record high temperatures are possible Sunday afternoon.

- Low humidity and a gusty westerly wind combine with the heat to produce elevated to critical fire weather conditions for much of the region beginning mid-afternoon Sunday. The dry, warm, and breezy conditions persist across southwest Wyoming on Monday.

- A cold front sweeps south Sunday night and Monday morning providing cooler air to Wyoming for Monday and Tuesday, especially in northern and central Wyoming. Temperatures will be 10 to 20 degrees, and as much as 25 degrees, cooler than Sunday.

- The upcoming work week looks mostly dry with a slow warming trend beginning midweek. Above normal temperatures likely return by Thursday.

UPDATE

Issued at 1200 PM MDT Sun Aug 2 2026

An upper low in the Canadian Rockies is keeping warm west-southwest flow across western and central Wyoming Sunday. Cirrus clouds have been streaming across the region within this pattern, allowing for standing wave clouds to form downstream of the Absaroka, Bighorn, and Wind River Ranges Sunday morning. Similar to Saturday, 700mb temperatures climb to around 20C leading to another hot day. More records are in jeopardy today. Heat Advisories remain in effect until 10 PM. West-southwest wind increases between 1 PM and 3 PM Sunday afternoon leading to critical fire weather conditions for many lower elevation locations until around sunset. A Red Flag Warning continues until 9 PM Sunday. The atmosphere is dry with surface dew points in the 20s and 30s and precipitable water below one-half inch. The latest KRIW 18Z sounding shows it being very dry up to 300mb. There does appear to be just enough 500-400mb layer moisture across far southern Wyoming to generate some weak virga showers off the Uinta Mountains late Sunday afternoon. Several CAMS also hint at this possibility. These would do little more than generate gusty outflow wind across the southern-third of Sweetwater County.

An initial surface cold front is still on-track to push through areas east of the Continental Divide Sunday night. A better push comes during the day Monday as a shortwave trailing the upper low moves east through Montana. Gusty north wind 15 to 30 mph and much cooler temperatures follow the front, with daytime highs from the lower 70s to lower 80s east of the Continental Divide. West of the Divide, Red Flag Warnings continue due to low relative humidity and a continuing westerly wind 15 to 30 mph.

DISCUSSION

Issued at 1236 AM MDT Sun Aug 2 2026

It certainly has been a hot stretch in Wyoming through July and starting August. For example, at the humble Riverton Weather Abode, of the past 29 days, 28 have averaged above normal. And the one day that was below average, July 23rd, was only 0.2 degrees below normal. We have had 7 high temperatures over 100, we typically average less than 1 a year. And we will almost certainly have another one today. However, there is something moving toward the area that will bring a welcome break from one of the hottest summers we have had in quite a while. More on that later in the discussion.

But we have one more scorching hot day to get through. We had several record highs that were broken or tied yesterday, including an all time August record high temperature at the Riverton airport. It was also the first time it has been 100 at the airport in the month of August (since 1996 when the ASOS was commissioned). The 700 millibar temperatures look largely unchanged from yesterday, so the high temperatures forecasted for Sunday also look relatively unchanged. With a southwesterly breeze developing, the areas that will be warmer will be the downslope locations. These include the southern Bighorn Basin, the Wind River Basin and Lander Foothills and portions of Sweetwater County. We will likely see more daily record high temperatures today. Some all time August high temperatures records could also be in jeopardy. It still looks like elevations below around 5800 feet have at least a 1 in 2 chance of high temperatures over 100F. As for highs of 105F, the 1 in 2 chance is largely below 4500 feet, mainly in portions of Fremont County as well the Big Horn Basin from Thermopolis to Worland. And the gusty breeze will also bring increased fire weather concerns. This, combined with relative humidity falling as low as 5 percent, will bring at least elevated fire weather to the entire area. A Red Flag Warning is in effect for much of the area, and we will continue it. I did give some thought to including Natrona County, but still have some doubts if the wind will be of sufficient strength or duration. Nevertheless, burning is strongly discouraged anywhere in western and central Wyoming today.

The relief from the heat for some will come in the form of a cold front dropping southward out of Montana tonight and tomorrow. It will begin to weaken as it moves through the area Monday, but all areas will see a drop in temperatures. The most pronounced drops will be across northern Wyoming where places Cody could see temperatures 25 degrees cooler than today with it feeling more like September. Most locations East of the Divide will see around a 15 to 20 degree drop in temperatures, with some locations seeing the coolest temperatures since June. It will also cool off West of the Divide, but not as much. However, 8 to 15 degrees will still feel better. We still have fire weather concerns on this day though. In northern and central Wyoming, the cooler temperatures and somewhat higher humidity should keep conditions below critical despite a gusty northerly breeze. Much of southern Wyoming will still have humidity under 15 percent though. And with the continued wind with the front in the area, critical fire weather still looks likely so the Red Flag Warning will be continued.

Tuesday looks like the coolest day across much of the area. There will still be a bit of a breeze and humidity remains low so we may need more fire weather highlights for this day as well although it is more borderline. We will have more time to look at that in future shifts. Following that, the ridge should again build across the desert southwest and then build back northward into Wyoming. This means temperatures rising again by Wednesday with above normal temperatures again likely from Thursday into next weekend, with 90s once again likely in many of the lower elevations. As for any precipitation chances, there are rather slim pickings. A weak shortwave will move across northern Wyoming and may bring a few showers and storms Tuesday afternoon or evening but with little moisture available coverage looks rather sparse. Mainly dry weather then continues for the rest of the week. There are some indications in some of the long range guidance of the ridge weakening early next week and maybe some monsoonal moisture returning for early next week but a lot of uncertainty this far out. So, enjoy the brief break from the hot weather early this week because it will likely not last long.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1041 AM MDT Sun Aug 2 2026

There is high confidence in dry and VFR flight conditions through at least 18Z Monday. Gusty southwest to west winds are forecast at all terminals by 21Z, with gusts in the 20kt to 25kt range. Occasional gusts closer to 30kts are possible at KCPR, KJAC, and KBPI. These gusty winds are expected to diminish to 10kts or less by 03Z Monday at most terminals. KRIW is the exception with sustained northwest winds up to 16kts through the overnight hours. A cold front begins to push into Wyoming from the north after 05Z at KCOD and shift winds to be more from the northwest. All other terminals have a northwest to north wind shift after 11Z Monday as the cold front drops south. Smoke will be more noticeable across the state due to increased wildfire activity across the western United States, especially at KJAC.

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 1236 AM MDT Sun Aug 2 2026

A combination of very hot temperatures, humidity falling into the single digits and a gusty southwesterly breeze will bring elevated to critical fire weather to most of the area today. A cold front drops southward on Monday. Fire concerns should lessen across northern and central Wyoming as cooler temperatures and higher humidity moves in behind the front. However, in southern Wyoming, critical fire weather should continue with a gusty wind and relative humidity remaining below 15 percent.

RIW WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 10 PM MDT this evening for WYZ003>006-010- 011-013-016>020-023-025>030.

Red Flag Warning until 9 PM MDT this evening for WYZ275-276- 282-283-285.

Red Flag Warning until 9 PM MDT Monday for WYZ277>279-289.