textproduct: Western and Central Wyoming

KEY MESSAGES

- Conditions will be dry and temperatures rebound today and Wednesday, but daytime highs remain well below normal. The arrival of another weather system Thursday cools temperatures a few degrees and provides another round of precipitation.

- Widespread precipitation is expected Thursday, with upslope areas like Cody and Lander having the best chances for snow accumulation during the day.

- Early indications point to a warm and dry Memorial Day holiday weekend with widespread 75 to 85 degree daytime highs.

UPDATE

Issued at 1234 PM MDT Tue May 19 2026

Snow from yesterday is clear on satellite today, with a large portion of central and southern areas white. Melting will occur through the next couple days as daytime highs slowly increase. However, temperatures do remain on the cool side the next few days. As a result, Freeze Warnings are once again in effect for portions of the area that have seen an early start to the growing season. Lows tonight should be in the upper-20s to low-30s east of the Divide, where the warnings currently are.

DISCUSSION

Issued at 145 AM MDT Tue May 19 2026

Areas of clouds still linger over central and southern portions of the CWA this morning, as expected. Low clouds have developed in the Upper Green River Basin, in the wake of the residual snow that fell through Monday evening. Low clouds/fog is also expected to develop near Pathfinder Reservoir in southern Natrona County as well as far eastern Sweetwater County near Wamsutter and Creston Junction. These clouds are expected to last through mid-morning. Travelers on I-80 and US-189/191 should exercise caution due to the reduced visibility. Otherwise, clouds will continue to scatter out through the rest of the morning with partly cloudy skies by 18Z. There is a 20-30% chance for fog/low clouds to develop in the Wind River Basin and areas near Casper. Cumulus clouds will begin to develop over the western mountains after 18Z, with isolated virga showers possible over northern portions of Yellowstone NP, the Cody Foothills, Hoback Junction and Lander/Fort Washakie. Temperatures will be about 10 to 20 degrees below normal today, with sub-freezing temperatures expected again tonight for most areas except northern portions of the Bighorn Basin.

The warming trend continues Wednesday, but temperatures stay below normal for central and southern portions of the CWA. Conditions will be dry for most areas, with showers possible over far northern portions irt the next storm system approaching the Cowboy State from the north. Precipitation chances will be confined to northwestern portions Wednesday night, with snow levels between 7000 and 8000 ft, as the storm drops southward. The associated cold front will drop southward over the CWA through the overnight hours, extending from Buffalo to Kemmerer by sunrise Thursday morning. The front will then slowly push through Natrona and Sweetwater counties through the rest of the day. Most of the precipitation with this storm will occur along and behind of the front, being widespread across the CWA through the day Thursday. Rain could change over to snow along and north of a Meeteetse-to-Lovell line after 15Z, as the cold core from the storm pushes into the Bighorn Basin. The challenge will be if snowfall rates will be heavy enough to overcome the high May sun angle. Otherwise, any snow is likely to stay in grassy areas through the day. There could be a similar change over later in the afternoon at Lander. Both of these locations (mainly Cody and Lander) will have a good upslope component with north- northeast winds. There could be a 3 to 5 hour window for snow accumulation between 23Z and 04Z (5pm to 10pm), as the sun begins to wane in the evening. A leeside low will develop over the Black Hills around this time, generating a line of showers and thunderstorms over western portions of SD and NE. Drier air will quickly push in over western portions of the CWA as the storm moves over the aforementioned areas through the rest of the night into Friday morning. Precipitation will quickly end from west to east after 03Z as a result of the storm becoming better organized over SD/NE. However, precipitation looks to linger over Johnson and Natrona counties through the rest of the night. Rain or a rain/snow mix is likely at this time, with snow levels as low as 6000 ft. Initial snowfall amounts around 6 inches are forecasted over the Absaroka and Wind River Mountains and 6 to 10 inches over the northern half of the Bighorns.

Temperatures rebound more quickly on Friday, staying at or slightly below normal as the storm quickly exits over the Plains. A pleasant holiday weekend is shaping up, with highs in the 70s and 80s by Memorial Day.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1119 AM MDT Tue May 19 2026

Dry and VFR flight conditions are forecast through 18Z Wednesday. Diurnal mid-level clouds will increase in coverage through the afternoon hours. Mid-level cloud cover decreases after sunset and increases in coverage again Wednesday morning. These clouds will cause frequent mountain top obscurations. There is a 10% chance of a light rain shower around KCOD and KLND between 20Z and 02Z, with no impacts expected. However, the most likely scenario is that it will not reach the ground and remain as virga. Winds largely remain 10 kts or less at most terminals. KCPR and KRIW could see winds between 10 kts and 15 kts.

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

Freeze Warning from 9 PM this evening to 8 AM MDT Wednesday for WYZ005-006-011-016>020.