textproduct: Western and Central Wyoming

KEY MESSAGES

- Snow and wind (up to 60 mph) remain for portions of central and southern Wyoming, including around Lander, Casper, South Pass, and Interstate 80. Conditions should slowly improve through he remainder of the day, with any light precipitation ending by midnight.

- Warming trend Tuesday and Wednesday, with mostly dry conditions. Another weather system brings cooler temperatures and precipitation chances for Thursday.

- Currently looking favorable for warm and dry weather this coming holiday weekend.

UPDATE

Issued at 1235 PM MDT Mon May 18 2026

The snow and wind across the area has been mostly as forecasted. Greatest impacts were around South Pass and I-80, with winter travel impacts going into this afternoon. Conditions should slowly improve through the evening as snow decreases and winds diminish. As was the trend in the day leading to the start of the event, northern locations have not seen as much (or any) snow, so have ended the advisories there early. As the system exits, very cold temperatures remain in place, with lows tonight in the upper teens to mid-20s for a majority of the area. Cooler temperatures remain in place Tuesday and Tuesday night, with a very gradual warm up into the end of the week.

DISCUSSION

Issued at 240 AM MDT Mon May 18 2026

Rain changed over to snow in the Wind River Basin and across Sweetwater County just a few hours ago after 11pm Sunday night. Much of Natrona County is around 37F degrees as of 08Z (2am), with precipitation still falling as rain. The forecast remains on track this morning, with the threat of snow and wind impacting areas from South Pass southward into Sweetwater County. The 700mb low from this storm system will be passing close to the CO/WY border this morning, resulting in a tight temperature and pressure gradient. 700mb northeast winds of 50-60kt will occur from the Green Mountains/Rattlesnake Range into Sweetwater County. This will result in wind gusts of 60 to 70 mph occurring this morning over locations like South Pass down to the Rock Springs/Green River area. Windy conditions (wind gusts up to 35 mph) will be widespread across the CWA this morning as the storm system moves over CO this morning. Snowfall amounts of 2 to 6 inches is still expected across portions of Natrona County, the Lander Foothills and the eastern half of Sweetwater County. Travel conditions could be difficult this morning due to the blowing snow and icy roads. Impacts from snow accumulations on roads is likely to only last through 15Z/16Z (9am or 10am) as it will be more difficult for the snow to stick due to the high sun angle. These impacts will begin to decrease through the morning, with areas like Lander and Casper improving first as snow begins to end toward midday. Impacts along I-80 will last the longest due to the proximity of the 700mb low, but is expected to wane between 18Z and 21Z as snowfall ends. Winds will be decreasing across the area after 18Z as well, with the stronger winds of 35 to 40 mph continuing from South Pass southward into Sweetwater County and decreasing through the afternoon. Needless to say, temperatures will be anywhere from 5 to 25 degrees colder today and about 15 to 30 degrees below normal.

Winds will continue to decrease this evening, as the storm system quickly exits over the Central Plains and light winds (10kt or less) expected for most areas by 06Z Tuesday. Fog development could occur as late as sunrise Tuesday morning as clouds are expected to remain in place across central and southern portions of the CWA through much of the night tonight. Dry and warming conditions are expected Tuesday and Wednesday, with another Canadian storm system impacting the area on Thursday. This system doesn't look to be as cold as today's storm and snow levels staying around 7000ft at this time. Model guidance remain split at this time, but confidence is medium for a mainly dry holiday weekend for at least 2 of the 3 days.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1235 PM MDT Mon May 18 2026

A spring system will continue to impact the area this afternoon, now focused mostly east of the Divide. KCPR, KLND, and KRIW will hold on to MVFR to IFR conditions for the next few hours before conditions begin to improve as the system pushes east. However, additional showers are expected to develop across the western mountains, impacting KBPI and KPNA this afternoon and evening with IFR flight conditions. This is expected to largely remain farther south and east of KJAC. Activity should wane everywhere after 06Z Tuesday, with clouds decreasing from west to east overnight. If skies clear quick enough fog may be an issue at several terminals after around 10Z. For now, we are most confident at KBPI and KRKS, though fog potential will also need to be watched for at KCPR, KLND, and KRIW.

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

Winter Weather Advisory until 6 PM MDT this evening for WYZ014- 016-017-026>029.

Winter Storm Warning until 6 PM MDT this evening for WYZ015- 018>020-022-030.