textproduct: Western and Central Wyoming

KEY MESSAGES

- Another warm day today with isolated to widely scattered showers and thunderstorms (a 20 to 30 percent chance). Coverage will be similar or less than yesterday.

- Record high temperatures are likely this weekend and possibly early next week with some all time record high temperatures possible. The hottest day is likely to be Sunday.

- Very low humidity will bring elevated fire weather Friday into early next week. Critical fire weather is possible in northern Wyoming Sunday afternoon.

DISCUSSION

Issued at 151 AM MDT Thu Jul 9 2026

We still have a few light showers in central portions of Wyoming early this morning as we still have a bit of CAPE in the atmosphere. Nothing heavy, and barely any lightning, just a few showers. At this point, any amount of moisture is a good thing.

And it looks like it will be another day of convection. There could be some this morning though, especially in portions of Johnson and Natrona County where guidance is showing some CAPE this morning, so we added around a 1 in 5 chance of a shower, it may end up just being virga though. Otherwise, the trend of decreasing coverage of convection continues as precipitable water values continue to drop. Again, the main chance will be East of the Divide with areas to the west largely dry with less than a 1 in 10 chance. For once, we don't have any kind of risk from the Storm Prediction Center. The main threat will be, as it always is this time of year, strong wind gusts. Models soundings continue to show inverted V signatures and with some dew point depressions approaching 50 degrees, wind gusts of 50 mph will be possible with any shower or thunderstorm. This looks like an earlier show with most showers ending after sunset and all over by midnight. Temperatures should be similar to yesterday, quite warm but fairly normal for July.

Tomorrow is where we begin to transition from thunderstorms to heat. Drier air will continue to push eastward across the area, dropping precipitable water levels even more. There may be just enough moisture and instability to squeeze out very isolated afternoon showers and thunderstorms, this would be mainly in Johnson County where a bit more moisture will linger and possibly the mountains with a bit of high elevation heat source. Coverage will be very sparse though, with a capital V and a capital S, less than 5 percent of the area. Temperatures will also begin to rise, approaching 100 in the warm spots like the Bighorn Basin and widespread 90s East of the Divide in the lower elevations. This is hot, but nothing unusually for the middle of July, climatologically the warmest time of the year.

Things really change on Saturday. Strong ridging over the desert southwest will begin to build northward, with 500 millibar heights reaching 5970 meters by days end. At the same time, 700 millibar temperatures will rise to as high as 21 celsius. This means a very hot day. Reasoning for today remains the same, most locations below 5200 feet East of the Divide have at least a 1 in 2 chance of high temperatures over 100 degrees, with the warmest spots like from Thermopolis to Greybull in the Bighorn Basin have an almost 100 percent chance. Some record high temperatures are certainly possible on this day. And, with the warm temperatures aloft and much drier air moving in, the chance of convection will be basically zero.

But this is only the appetizer, with the main course likely to be on Sunday. This is when the ridge will be centered over Wyoming, with some models giving 500 millibar heights as high as 6000 meters. The 700 millibar temperatures may climb as high as 24 degrees celsius. All this adds up to a very hot day, possibly one we haven't seen in a long time. The NBA ensemble gives a greater than 1 in 2 chance of 100 degrees in all locations below 6000 feet, with an almost 100 percent chance below 5500 feet. And this includes some places that don;t see 100. Rock Springs has around a 3 in 5 chance of over 100, and even Jackson has a 1 in 3 chance. The lower elevations of the Bighorn Basin have at least a 4 out of 5 chance of high temperatures over 105 degrees on this day. And the warmest spots, like Greybull and Basin, have a 1 in 2 chance of reaching 110. This is the most likely day to see all time record highs broken, especially in locations that have a shorter period of record.

As for heat highlights, I had mixed thoughts on this. The main reason is the humidity, or more specifically the lack of it. The lower elevations will have widespread single digit relative humidity, with some locations falling as a 3 percent on Sunday. This has an impact on the apparent temperatures, which is what we base heat highlights on. For one, the apparent temperature will be below the actual temperature by 5 or 10 degrees. Also, with the dry air, almost all locations should cool off at least into the 60s at night. The one place I could see an excessive heat watch is the Bighorn Basin, but this would mainly be for Sunday. Heat advisories look more likely at this time, there is still time so we will punt to day shift to take another look.

And there is one more concern for Sunday. The NBM ensemble is giving a greater than 1 in 2 chance of wind gusts over 30 mph Sunday afternoon north of a Meeteetse to Worland to Kaycee line. With the extremely dry conditions, we may have to consider Fire Weather Highlights for Sunday afternoon.

There should be some slight, and emphasis on slight. cooling on Monday, be probably only by 3 to 5 degrees. One hundred degree high temperatures will still be very widespread across the lower elevations. One this day, there may be just enough moisture to come around the backside of the ridge for isolated storms in the western mountains, but the chance is only around 1 out of 10. Chances of convection then slowly increase each day, starting mainly in western Wyoming on Tuesday and then spreading eastward as the ridge slowly moves eastward and moisture rotates in around the backside of it. Temperatures will cool at first in the west, but likely remain well above normal through the forecast period. Very hot temperatures continue Tuesday before some cooling moves in for midweek East of the Divide. But even with some cooling, temperatures should remain well above normal through most of next week.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1000 PM MDT Wed Jul 8 2026

VFR conditions prevail over the next 24 hours for most sites. A few isolated showers linger this evening, but these should largely end by midnight (09/0600Z). Mid-level cloud decks hang around in central Wyoming overnight into the morning hours, and by mid-morning, CPR could see some virga (light showers evaporating before they hit the ground). These could lead to some unexpected gusts from variable directions at (and above) CPR during the morning hours.

During the afternoon hours, LND and RIW each have a slight chance (PROB30 groups added) of afternoon thunderstorms with erratic, gusty (35 to 45 kt) winds. Other sites have a smaller but non-zero chance of an isolated storm nearing the airport, so added BKN and OVC decks at these sites to hint at the possibility. RKS now looks to remain south of the better lift, so removed the PROB30 at that location for the 06Z set of TAFs. Any isolated storms and showers quickly end after sunset Thursday.

RIW WATCHES/WARNINGS/ADVISORIES

None.