textproduct: Western and Central Wyoming

KEY MESSAGES

- This afternoon and evening's weather will be similar to Wednesday, with seasonably warm temperatures (near normal to 3-5 degrees above) along with isolated to widely scattered showers and thunderstorms. The storms are expected from around Star Valley and Kemmerer northeast over the mountains into the Bighorn Basin and Bighorn Mountains. Northern Johnson County may see some stronger storms today. Any shower or thunderstorm could have strong wind gusts over 40 mph.

- Friday will see isolated showers and thunderstorms in the afternoon and early evening under partly cloudy skies. High temperatures will be from the upper 70s to around 90, just a couple of degrees above normal for most locations.

- Saturday (the Fourth of July) will be mostly sunny with highs in the 80s to low 90s (about 5-8 degrees above normal) with some breezy and gusty afternoon and early evening west wind.

- Sunday will be the hottest day of the weekend with high temps 8 to 15 degrees above normal from the mid 80s to around 100. Partly cloudy skies in the afternoon will ring isolated showers and thunderstorms to parts of northwest and northern WY.

UPDATE

Issued at 1240 PM MDT Thu Jul 2 2026

The previous forecast for this afternoon and evening largely remains on track, though have increased precipitation chances across western and central WY with the weak shortwave through moving northeast from the Great Basin across north-central WY. Convection already initiated before noon today from the Upper Green River Basin to the southern Absarokas. Have expanded isolated showers and thunderstorms southeast of there from Rock Springs/Green River toward South Pass due to early development of convective towers as see on visible satellite imagery. As mentioned previously, the large surface dew point depressions are expected to give rise to outflow wind gusts of 40 to 50 mph. High resolution models (CAMs) once again seem to be about 1-2 hours behind the curve on convective development. However, all are indicating an overall gusty late afternoon and evening of northwest wind across central and southern WY due to outflow from the storms to the northwest. SPC still has the northeast third of Johnson County in marginal risk of severe thunderstorms. Expecting a couple of storms in this area to produce 50+ mph wind gusts. Also expecting showers to linger across parts of northern WY until just past midnight. The outflow and passing shortwave trough will help some northerly wind to push into the Bighorn Basin and Johnson County this evening.

While there is not a distinctive shortwave trough expected on Friday, popcorn convection is expected during the afternoon hours and early evening hours as a result of weak troughing across southern Montana on the downstream side of the ridge. At this time the most favorable area seem to be the middle Wind Rivers eastward into the Wind River Basin (which may lead to strong outflow wind gusts in the afternoon) as well as across far northern WY in the early evening hours. Once again, SPC is indicating a slight risk of severe thunderstorms across a sliver of eastern Johnson County because of the potential for strong storms across northeast WY. The best time for these storms appears to be from about 2 to 5 PM.

DISCUSSION

Issued at 230 AM MDT Thu Jul 2 2026

Happy Independence Day everyone! This is actually the day we declared Independence from England since the Continental Congress voted and declared independence on July 2nd, not July 4th. Americans first saw the Declaration of Independence on July 4th, that is when we celebrate.

And mother nature will help us celebrate by providing some of the natural fireworks see is infamous for, AKA thunderstorms. The pattern continues to show the Death Ridge across the Eastern Unites States. We continue to have a mean trough over the western portions of the USA but it continues to flatten. At the same time, another shortwave will be moving over the top of the ridge and bringing another round of thunderstorms. Parameters are fairly similar to yesterday. There will be some CAPE but nothing off the charts (generally maxing out at around 500 J/KG across the west and in Johnson County, with less basically none in southeastern portions of the area), and lifted indices generally dropping down to minus 2. The limiting factor will again be moisture, with most areas having below the seasonal average (the average is around 0.55 inches in early July). There will be some factors in favor of storms though. For one, lapse rates are very steep, over 9C/km in some locations. There will also be a decent amount of directional shear around. As for the outlook, the marginal risk remains in a similar location, largely East of Interstate 25 in Johnson County. As for threats, by far the greatest threat would be strong wind gusts. All areas have at least a 35 degree dew point depression, with some locations East of the Divide having as much as 65 degrees. Model soundings also show high cloud bases, increasing the chance of dry microbursts. This is a day when any thunderstorm, shower or even cumulus cloud could collapse and produce strong wind gusts. This looks like it could be one of those infamous "Little Green Blob" days. As for hail, the main threat would be in northern Wyoming where there is a bit more moisture. Coverage looks sparse though, generally less than a 1 in 3 chance across the north to less than 1 in 10 in southeastern portions of the area, so most locations should not see one. Most convection should end around sunset, although a few showers may linger through the night. Temperatures should average close to yesterdays, perhaps a few degrees warmer, so warm but not really hot.

Flow will essentially become zonal by Friday, with even drier air pushing into much of the day. Models have trended a bit drier on this day as well, with most of any convection largely across northern Wyoming as another shortwaves tops the ridge. Once again, the main threat from any shower or thunderstorm would be strong winds. Chances on this day are 1 out of 4 or less for all locations. As for temperatures, once again similar to Wednesday with warm but not overly hot conditions. And as far as fire weather, humidity will be rather low. However, wind should remain light to moderate for the most part, so no fire weather highlights are anticipated at this time.

Now on to the celebrated Independence Day, July 4th. And at this time, conditions look fairly nice. It will be a hotter day across the area. Not hot as a firecracker, but it will definitely feel like mid summer. Almost all the lower elevations will have highs at least in the 80s with many locations East of the Divide cracking 90. The best news is that shortwave ridging should be over the area, bringing upper level divergence. This, combined with precipitable water values only 80 percent of normal, means less than a 1 in 10 chance of a shower or thunderstorm anywhere in the area. The main concern will be the very low humidity, falling close to the single digits in some locations. However, once again wind is expected to remain light to moderate.

The chance of thunderstorm looks to return Sunday and Monday, although convection looks to remain relatively isolated and largely across northern Wyoming. Tuesday may bring a better chance of storms as a weak cold front passes through and a bit of moisture return may increase coverage somewhat. As for temperatures, the heat looks to peak on Sunday when some of the warmer spots in the Bighorn Basin may get close to 100 degrees. Things turn a bit cooler for the middle of the week with more clouds and chances for storms but not cool by any means.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 540 PM MDT Thu Jul 2 2026

Ongoing scattered thunderstorms across the western half of Wyoming persists through at least mid-evening as a weather system tracks slowly across the region. This system slowly progresses eastbound between 06Z-12Z/Friday with lingering showers until early Friday morning. Some early evening PROB30 groups continue until at least sunset, with KCOD and KWRL lingering longest as the system pushes east. The least likely candidate for any storms remains KCPR, with KRKS a close second. Cloud cover clears the area late tonight, but enough mid-level moisture lingers to allow for another round of storms Friday afternoon. However, coverage is expected to be less than Thursday. VFR conditions prevail at all terminals through the forecast period. Most terminals see a diurnal westerly wind around 10 kt with occasional gusts to around 20 kt beginning mid-day Friday.

RIW WATCHES/WARNINGS/ADVISORIES

None.