textproduct: Western and Central Wyoming

KEY MESSAGES

- An approaching weather system will bring a good to likely chance of showers to much of the area this morning, with most rain across western Wyoming through the day today. Rain chances will spread into the central basins and across the south this evening.

- Accumulating snow is likely today over the western mountains and over the northern mountains Sunday, especially above 9500 feet.

- Temperatures will be much cooler today and Sunday as a result of the widespread rainfall, rebounding next week.

DISCUSSION

Issued at 144 AM MDT Sat May 30 2026

Showers will continue to increase early this morning as the upper level low approaches, mainly occurring over western and southern portions. A sfc reflection of the low will develop near La Barge/Farson by mid-morning and track to the northeast over the Divide and into the Wind River Basin through the rest of the morning into the early afternoon. Showers will rotate to the northwest during this time, with showers being roughly confined along and west of a Cody-to-Rock Springs line. Dewpoints will drop into the middle 30s over Natrona County, eastern portions of Fremont County, far southern portions of the Bighorn Basin and Johnson County by 21Z as a result of southerly winds shunting the available moisture northward. Most areas east of the Divide are likely to stay dry during the afternoon. Northern portions of the Bighorn Basin and Johnson County will be the exceptions, with Johnson County having the higher chances. A boundary will be in place that could provide a trigger for any shower/storm to develop in this area, but will quickly move northward due to the aforementioned southerly winds pushing the boundary northward. The potential for any strong storm will be in this area, with forecasted CAPE values of 1000-1500 J/kg and LI values < -6. Shear will not be strong, so instability will be the main driver for any severe storm. Otherwise, isolated to scattered thunderstorms will be embedded within the aforementioned shower activity over the west this afternoon.

The upper level low will slowly track over the Cowboy State through the overnight hours tonight, reaching the northeast corner of the state by 12Z Sunday. Showers and will continue over western portions and Sweetwater County early in the evening, with additional showers developing over the Bighorn and Wind River Basins after 06Z on the backside of the low. Showers will increasingly become confined over northern portions after 12Z Sunday as the upper low continues its progression over eastern MT/the western Dakotas through the day. Winds will increase across the CWA Sunday, as the gradient tightens in the wake of the departing low. Gusts of 25 to 35 mph will occur through much of the day, quickly decreasing through the evening.

Rainfall amounts over 0.10" from today through Sunday are still forecasted to occur along and north of a Kemmerer-to-Riverton- to-Kaycee line, with far southwestern portions of Sweetwater County included. The heaviest amounts of 0.75 to 1" are still expected over northern and northwestern portions of the CWA. Flooding or rain-on-snow is not expected from this event, as most snow in the 9000 to 10000ft range (SnoTel sites) is gone already.

Isolated showers and thunderstorms will be possible Monday, as a shortwave moves over the Cowboy State. Winds aloft will be southwesterly as a trough develops over the Northern Rockies from the remnants of today's upper low. Most of the convection looks to develop over the western mountains between 19Z and 21Z and quickly push eastward over areas east of the Divide and Sweetwater County. Additional showers will move over northwestern and northern portions late in the afternoon into the evening, as a second shortwave rotates through the base of the trough. Tuesday looks to stay mainly dry, with west-southwest winds aloft keeping any potential convection over far eastern portions of the state. Showers and thunderstorms will be possible again Wednesday and Thursday, with dry conditions returning for Friday. Temperatures will be above normal these days, with highs in the upper 70s into the 80s.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 517 AM MDT Sat May 30 2026

Rain showers and embedded thunderstorms will be ongoing across Wyoming throughout the TAF period, with the greatest potential for thunderstorms occurring between 15Z Saturday and 01Z Sunday. Conditions will frequently change between VFR, MVR, and IFR at most terminals through the TAF period. The most likely period of MVFR or IFR flight conditions is from the start of the TAF period through roughly 03Z/04Z Sunday. Terminals with the least impacts will be KCPR, KRIW, KLND, and KWRL. Expect winds to be between 08kts and 15kts the entire period at all terminals. Wind gusts of 20kts to 30kts will be most common at KCOD, KCPR, KRIW, KRKS, KPNA, and KLND after Saturday morning through Saturday evening. However, expect gusty and erratic winds around any thunderstorms. Mountain obscurations will be common throughout the entire TAF period.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.

RIW WATCHES/WARNINGS/ADVISORIES

None.