textproduct: Western and Central Wyoming

KEY MESSAGES

- Mainly rain continues in the eastern basins this afternoon changing over to snow after sunset. Highest impacts across the Bighorns to northern Johnson County.

- Continued active pattern with little impacts expected Monday through Wednesday.

- Dry conditions and a warming trend for the end of the week and into next weekend.

UPDATE

Issued at 1254 PM MDT Sun Apr 26 2026

Moisture with the latest wave continues to move across the state. Precipitation will be greatest between 6pm and midnight tonight, with a mix of rain changing to snow. A SW/NE band is expected to develop, being the focus of the highest amounts of precip. Models have been nudging this back slightly north and south the past 24 hours, but is focusing in the eastern Sweetwater/ SE Fremont/Natrona/southern Johnson Counties. Snow ratios with this band will be held down both by high moisture content and ground melting most snowfall as it falls. So the center of this band would produce around 0.50 to 0.75" melted liquid, with areas around it around 0.20 to 0.30".

Farther north along the I-25/I-90 corridors, precip will change over to snow earlier, and will be accompanied by gusty north winds around 30mph during the evening. While snow accumulation will be slow, roads will become slushy and slick, along will lower visibilities due to blowing snow. Northern Johnson County remains in a Winter Weather Advisory through tomorrow morning for this setup. The Advisory also covers the Bighorn Mountains, which has a better opportunity for snow accumulation of 6 to 8 inches along Powder River and Granite Passes.

DISCUSSION

Issued at 130 AM MDT Sun Apr 26 2026

IR currently depicts increasing cloud coverage pushing in from the southwest with the next system over Nevada to northern Utah as it progresses to WY by early Sunday morning. WV shows the main finger of the PFJ pushing around an upper level low along the MT/Canada/ND tri-point with a jet max of around 120kts around the base of the L/W trough positively oriented extending southwestward to northern California. This next weather system with progress northeastward through the day Sunday as the PFJ moves northward as well with ample support and deepening due the increased divergence aloft out of the base of the aforementioned trough. Southwest flow will be conducive to increased precipitation for points east of the Divide and the southern areas of the state. Highest impacts to the western Winds (although to higher elevations and nothing of note to South Pass, but mostly to the passes of the Bighorns to northern Johnson County. Precipitation type for much of Sunday for eastern Basins will remain rain until sunset before it switches over to snow. There is even a bit of instability of around 100-200 J/kg across eastern Sweetwater to Fremont/Natrona Counties for a few possible rumbles of thunder Sunday afternoon. Storm chances will end before sunrise loses what warmth there will be for instability as precipitation changes over and starts to fill in across the Wind River Basin to eastern counties towards midnight and through the overnight hours.

Snow accumulations for the Bighorn mountain passes are likely to range from 6 to 10 inches (80-90% confidence) trickling down across northern Johnson County into early Monday morning. Highest wind speeds will be across this area pushing 30 to 35 mph. Coupled with an inch or two of snow (60-70%), expect some travel impacts before sunrise and lingering into the Monday morning commute. As such, a winter weather advisory has been issued to account for this, with any lingering snow and impacts to push east by mid morning Monday. The remainder of Monday will be much less active with some convection possible for Sweetwater County south of the I-80 corridor with the next shortwave skirting further south as the main upper level low starts to push east.

Overnight Monday into Tuesday, the low continues to the east and lift more north as the PFJ brings in a more northwest flow aloft. Precipitation will be more limited to the northern half of the CWA bringing some minor impacts to the northern mountains and Yellowstone as the jet weakens in support of the upper level low with decreased divergence in its wake. Wednesday will continue this trend as the low is even further east and impacts expected to be across the Bighorns to eastern counties as the cooler trend will come to an end. There after, expect some weak upper level ridging to build in from the southwest that will give way to drier conditions and a slight warming trend going into next weekend. The next thing to keep an eye on will be early the following week with a low/trough to the southwest dependent on if it remains closed or becomes an open wave. Stay tuned, but the short term looks to remain active brining some much needed moisture to much of the area.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1111 AM MDT Sun Apr 26 2026

An active weather period. Widespread precipitation chances occur through today and into Monday morning. Individual TAFs vary greatly by precipitation type, timing, and cloud ceilings. However, the overall trend is for MVFR and IFR prevailing conditions most locations. This afternoon, showers become more scattered, so rain may not prevail, but should occur frequently enough that prevailing groups were used. A cold front then moves through starting this evening, bringing a north wind shift (strongest for KCOD, KCPR, and KWRL) and colder temperatures, transitioning rain to snow. Precipitation chances trend down overnight, with models in disagreement in how quickly cloud ceilings increase to VFR. For now, have TAFs with more pessimistic ceilings, keeping MVFR clouds ceilings towards the end of the 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

Winter Weather Advisory until 9 AM MDT Monday for WYZ008-009.

Winter Weather Advisory from 6 PM this evening to 9 AM MDT Monday for WYZ010.