textproduct: Western and Central Wyoming

KEY MESSAGES

- It will be a near-record hot weekend, with basins east of the Continental Divide seeing highs near or over 100 degrees. Many higher-elevation basins and valleys west of the Divide will see highs into the 90s.

- Elevated fire weather conditions are likely through early next week, with Sunday and Monday being the days of greatest concern.

- A cold front will push through the region Sunday night into Monday, causing temperatures to drop 15 to 20 degrees east of the Divide, and drop by about 10 degrees west of the Divide.

UPDATE

Issued at 200 PM MDT Sat Aug 1 2026

No major changes or shifts in the running forecast over the next 7 days. Both today and tomorrow continue to look near-record hot, with temperatures about 15 degrees above seasonal normals. The air mass will also be very dry, and breezes that develop on Sunday and into Monday will also cause critical fire weather conditions for areas where fuels have been deemed susceptible by land management agencies. For these reasons, Heat Advisories and Red Flag Warnings have been posted.

Sunday night into Monday, the strong ridge aloft will be pushed east by a trough moving across the Pacific Northwest. The surface cold front will cool temperatures off by about 20 degrees east of the Divide, while basins and valleys west of the Divide will cool off by about 10 degrees Monday. Typical mid- summer heat returns by mid-week, with warmer than usual temperatures late in the week.

DISCUSSION

Issued at 1237 AM MDT Sat Aug 1 2026

We are now officially two thirds of the way through meteorological winter (it runs from June through August). And, unless you've been living under a rock, it has been a hot one. Some of our major climate sites have had their warmest July on record. This includes Lander, which has records going back to 1892. And this looks to continue this weekend. However, we may have some welcome relief on the way for portions of the area early next week.

However, we will have to run the heat gauntlet this weekend before we get to the relief. (Was waiting to throw the word gauntlet in, I loved that video game back when I was a teenager in the 80s.) Anyway, the reasoning for the forecast for the weekend remains the same as yesterday. Another heat dome will build northward over Wyoming and bring a couple of days of very hot and in some cases record breaking heat. We will still have 700 millibar temperatures climbing to 21 to 22 celsius on both Saturday and Sunday, and this translates to all lower elevations seeing high temperatures at least in the 90s. For today, most elevations below 5000 feet have at a minimum a 1 out of 2 chance of high temperatures over 100 degrees, with the lower elevations of the Bighorn Basin (generally below 4000 feet) having a 1 out of 2 chance of high temperatures over 105. Sunday still looks like the warmest day, as a gusty southwesterly breeze develops ahead of a cold front dropping toward the area from Montana. This should allow temperatures to be a few degrees warmer, with locations having at least a 1 in 2 chance of highs over 100 now under 5500 feet. And in the areas most prone to the downslope warming, like the Wind River Basin, southern Bighorn Basin and even around Casper, could be even warmer. The National Blend of Model ensembles give at least a 1 in 3 chance of highs of 105 below 5000 feet in these areas. This is the day when some all time highs for the month of August may be set. It does not look quite as hot as on July 12th though, so all time record highs should be safe for most. The one that may be in jeopardy is the Sweetwater County airport, where we could reach the all time record high of 98. With this, we will keep the heat advisories going as is. As for precipitation, I can't completely rule out a very isolated virga shower over the mountains, but the chance is less than 1 out of 10 and was left out of the forecast.

The other concern on Sunday will be fire weather. Humidity will will be very low through the weekend, falling under 15 percent for many areas and many of the lower elevations seeing relative humidity in the single digits. Wind should remain light to moderate on Saturday. The gusty southwesterly breeze then develops on Sunday, bringing the possibility of critical fire weather. The low humidity is a slam dunk, the wind is still borderline in some areas though. For now, we will keep the fire weather watch going and let the day shift take another look.

As for Monday, those of your who are Gen X or older may remember an commercial for antacid where it asks how do you spell relief? Well, the relief from the heat will be spelled C-O-L-D F-R-O-N-T. It will drop slowly into northern Wyoming Sunday night, reaching the Continental Divide during the day on Monday. This will bring some cooler temperatures, generally about 15 to 20 degrees cooler than on Sunday. A few places in far northern Wyoming may have a brief taste of September, with high temperatures only in the 70s. It will remain rather hot across southern Wyoming though. In addition, with the front in the area, a gusty breeze will continue. With the cooler temperatures and somewhat higher humidity across northern Wyoming, fire weather should drop below critical. However, with the gusty wind and humidity around 10 percent continuing in southern Wyoming, critical fire weather should continue another day. So, we will continue the fire weather watch. The one thing the front will not bring is moisture. We can't completely rule out a shower over the far north, but the chance is less than 1 out of 10.

Mainly dry weather looks to continue through much of next week as well. A weak shortwave may bring a stray shower or storm to northern Wyoming Tuesday evening, but the chance is less than 1 out of 5 given the lack of moisture. The general trend for much of next week will be for the ridge to build back northward and bring warmer temperatures back to the area. Above normal temperatures look likely toward the end of next week and next weekend, but extreme heat looks unlikely at this time, just temperatures running a few degrees above seasonal averages.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1055 AM MDT Sat Aug 1 2026

All terminals to be VFR through the forecast period. Little more than some high clouds increasing overnight. Terminals west of the Continental Divide see westerly 10-18kt winds Saturday afternoon until around sunset. East of the Divide terminals see speeds 12kts or less.

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 220 PM MDT Sat Aug 1 2026

Very hot temperatures today and tomorrow (Sunday) will lead to afternoon relative humidities dropping into the single digits (basins) to low teens (mountains). Today's winds are very light, and will prevent critical fire weather conditions. However, breezes and typical Wyoming gusts of 25 to 35 mph develop on Sunday as the ridge aloft breaks down, leading to critical fire weather conditions. Most of the region will be under Red Flag Warnings starting on Sunday. Cooler and slightly more moist air comes in from the north Sunday night, raising RH for basins east of the Divide on Monday, but locations across western and southern Wyoming will not receive as much of this cooler air, and remain dry and breezy Monday, with Red Flag conditions continuing there until Monday night.

RIW WATCHES/WARNINGS/ADVISORIES

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

Red Flag Warning from 1 PM to 9 PM MDT Sunday for WYZ275-276- 282-283-285.

Red Flag Warning from 1 PM Sunday to 9 PM MDT Monday for WYZ277>279-289.