textproduct: Western and Central Wyoming

KEY MESSAGES

- Warm today with highs in the upper 60s and low 70s. Isolated (10%- 15%) virga / light shower potential across Yellowstone National Park, the Absarokas, and the Bighorn Basin after 5PM/6PM MDT.

- Expect highs in the 60s on Saturday with breezy 20 to 35 mph winds. Shower and thunderstorm chances (40% to 80%) along and east of the Divide, especially across Johnson and Natrona Counties, much of Saturday.

- Dry and warm Sunday through most of next week, with widespread highs in the 80s by Monday. Breezy winds and minimum relative humidity values below 15% will contribute to elevated to near critical fire weather conditions much of next week.

UPDATE

Issued at 1231 PM MDT Fri May 8 2026

Northwest flow aloft continues with ridging west of Wyoming. Expect a warm afternoon with high temperatures in the upper 60s and low 70s. There is consensus among multiple deterministic guidances that a vorticity maximum will traverse Wyoming beginning around 5PM/6PM MDT this evening ahead Saturday's shortwave. A slight uptick of mid- level moisture will accompany this evening's vorticity maximum, especially across Yellowstone National Park, the Absarokas, and the Bighorn Basin. Model soundings indicate dry low levels across these areas and high cloud bases above 10,000 feet AGL. This means that there is a low chance (10% to 15%) for isolated instances of light rain across and around the aforementioned locations. However, the most likely scenario is that little liquid will make it to the ground and that it will largely be virga from roughly 5PM/6PM today until after midnight tonight.

The forecast remains on track for a shortwave embedded within the northwest flow to traverse across Wyoming on Saturday. There is a slight uptick in moisture with this shortwave given the Pacific origin. An associated cold front will push down from the north and support showers and thunderstorms along and east of the Divide beginning Saturday morning. The greatest coverage of thunderstorms is still expected to occur across Johnson and Natrona Counties (60% to 80%) from Saturday morning through 6PM Saturday. Rainfall amounts are forecast to range from a trace to 0.10 inch across most areas east of the Divide. The Bighorns, Johnson County, and northeastern Natrona County have a 40% to 70% chance of seeing 0.25 inches of rain by Saturday night.

Moisture is expected to stay east of the Divide, which will leave areas west of the Divide dry with relative humidity values below 20%. There is a 60% to 80% chance that minimum relative humidity will be 15 percent or lower across Sweetwater County on Saturday afternoon. This low humidity, combined with gusty 25 mph to 35 mph winds (thanks to the tightening pressure gradient), will support elevated to near critical fire weather conditions across southern Wyoming on Saturday afternoon. Temperatures have remained consistent in a warm up to around 20 degrees above normal (80s!) most of next week. These abnormally warm temperatures along with dry and breezy conditions suggest that a week of elevated to near critical fire weather conditions is upon us.

DISCUSSION

Issued at 100 AM MDT Fri May 8 2026

Northwest flow aloft continues across the CWA as depicted on WV imagery with the PFJ now retreated to the northeast coming out of Canada through eastern Montana to northeastern WY to the Great Plains. IR shows subsidence pushing in from the west as the ample cloud cover is pushing east out of the area by sunrise Friday morning. A few scattered showers linger across eastern Fremont and into Natrona County that will diminish and exit the CWA before sunrise as well.

Convergence and dry slotting expected for Friday with warmer temperatures (~5 degrees warmer than Thursday) with dry conditions expected. Some breezy winds west of the Divide and across the wind corridor, but nothing exceptional with an overall weak to moderate pressure gradient across the CWA. The next subtle shortwave will propagate down the northwest flow dropping a weak frontal boundary in from the north come Saturday morning. This will bring some scattered rain showers and isolated thunderstorms by Saturday afternoon and evening with 40-50% coverage and confidence a bit more northeast than it was Thursday. The strongest storms look to be east of the Bighorns for Johnson/Natrona Counties where CAPE values look to be more intriguing for Wyoming standards ~250-350 J/kg. Gusty outflows look to be the hazard outside of any lightning to occur and something to keep an eye on. Nothing of high significance but any rainfall will help in these areas. Regardless, once the sun sets, any lingering shower activity will weaken and exit to the east before midnight and dry out come Sunday morning.

Sunday and into next week will see a stronger upper level ridge to build in to be more oriented across the Rockies. This will bring much warmer temperatures and dry conditions for several days. Afternoon high temperatures east of the Divide look to push well into the 80s with 70s to the west. Breezy conditions will lead to elevated fire weather conditions due to the low RH values and warmer temperatures, even with greenup now ongoing for all zones. The next weather system of note looks to be by week's end late Thursday into Friday that should bring a reprieve from the warmer temperatures and increasing precipitation chances once again.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1133 AM MDT Fri May 8 2026

VFR conditions are expected across the region over the next 24 hours. Mostly clear skies this afternoon, with increasing cloud cover for the northern half of Wyoming this evening.

Isolated rain showers develop overnight for the northern half of the state, with mid-level cloud layers. There is a 50% chance of brief hit-or-miss showers affecting WRL and CPR near and after sunrise Saturday, but heavy rain is not expected. Winds shift to become northerly Saturday morning as a subtle cold front pushes southward into the region from Montana, mainly affecting locations east of the Continental Divide. Gusts range from 20 to 30 kt with this cold front.

RIW WATCHES/WARNINGS/ADVISORIES

None.