textproduct: Western and Central Wyoming

KEY MESSAGES

- Scattered rain/snow showers this afternoon and evening with a steady period of light snow across portions of Natrona and Johnson Counties Friday morning.

- A hard freeze is expected to occur across nearly all lower elevations with temperatures in the teens and twenties Friday and Saturday mornings.

- Dry and warm conditions gradually return to the state over the weekend into the start of next week.

UPDATE

Issued at 136 PM MDT Thu Apr 16 2026

The system that has been talked about all week is finally working its way through the area. The previous discussion is still on track with only a few caveats. The associated cold front is gradually making its way south across the state currently. Unfortunately, the trend of a weaker more disorganized system persists and as a result, precipitation amounts and snow accumulations continue to lessen. The bright side is most higher elevation mountains will see some much needed moisture, the same cannot be said for the lower elevations. Convective showers will continue to pop up this afternoon ahead of the front with the best chances (40-70%) remaining across portions of central WY mainly Johnson and Natrona Counties along with portions of the Bighorn Basin. Precipitation likely falls as rain initially with these showers but as the colder air approaches there is a good chance for snow squalls to develop. These squalls will create some hazardous conditions for a period of time with lowered visibilities, gusty winds, and moderate to heavy snowfall. An isolated rumble of thunder cannot be ruled out nearby these developing squalls. A quick coating to inch or two may be possible on grassy surfaces with any squalls but warm surfaces may limit most accumulation. Once the sun sets these convective showers should dissipate and the next phase of this disturbance will begin. Thursday night into Friday morning looks to be the best period to see a prolonged period of light to moderate snowfall as flow becomes more favorable for portions of Natrona and Johnson Counties. This is where things went wrong in terms of precipitation for other locations, such as the Wind River Basin. Models have continued to show a more northwesterly flow develop, which is rather unfavorable. As a result, the period of snow for portions of the Wind River Basin has become more and more unlikely. Due to this,w snow accumulations have dropped to a generous 0.2 to 1.0 inches. This is likely on the higher side and its very possible that many areas may only see a few flakes with the initial frontal passage. Due to this, Winter Weather Advisories for the Wind River Basin, Lander Foothills, and Upper Wind River Basin have been cancelled. The other advisories remain in place as they still look to have the most favorable dynamics.

Aside from snow, the other impactful aspect of this system will be well below freezing morning lows on Friday and Saturday mornings. Low temperatures currently are forecast to range from the mid teens to upper 20s Friday morning. Colder temperatures are possible Saturday morning as skies look to clear out allowing for greater radiational cooling. Temperatures Saturday morning currently look to range from the low to mid teens west of the Divide and low 20s to upper teens east of the Divide. As a result, a hard freeze is likely for nearly all lower elevations. Due to the prolonged period of above normal temperatures and lack of below freezing overnight temperatures there is concern for sensitive vegetation. So Freeze Warnings have been issued for the lower Wind River Basin, Lander Foothills, and Bighorn Basin. Other locations such as Johnson and Natrona Counties will likely need freeze related highlights after Winter Weather Advisories expire on Friday. Otherwise, the previous forecast discussion remains of track for the weekend through next week.

DISCUSSION

Issued at 207 AM MDT Thu Apr 16 2026

There have times through my rather lengthy meteorology career that I have felt guilty for things. And this is a system when I am having these feelings. The last time I did the forecast, back on early Monday morning, it looked like we had a decent chance of some badly needed moisture across the area. However, trends for much of the area that need the moisture, like the Green River, Wind River and Big Horn Basins, have been for less and less moisture. At the time, chances looked rather good. Needless to say, chances have diminished substantially over the past few days.

Radar now shows the first area of precipitation moving into western Wyoming. The cold front is still back in Idaho, so snow levels remain fairly high right now, generally above 7500 feet. Snow will levels will gradually drop through the night and day. As for highlights in western Wyoming, these still look reasonable. Probabilistic guidance shows at least a 2 out of 3 chance of 8 inches or more across most of the warned area. Thought about a Winter Weather Advisory for the Salt and Wyoming Range, but the only areas with a greater than 1 in 2 chance of 6 inches of new snow or more are the highest elevation above the mountain passes. So, we will hold off for now. In the valleys and lower elevations, no location has more than a 1 in 6 chance of 4 inches or more, so no highlights here. Some snow will continue through Thursday night, but the bulk of the snow will fall through midnight with light snow following that. In Sweetwater County, with some surface instability, snow squalls will be possible late today and this evening with the front, mainly to the east of Rock Springs. Amounts here should remain under 3 inches though. The only areas with a greater than 1 in 3 chance are across far southern Sweetwater County where impacts will be slim to none. Any snow squalls could be handled by short fused statements.

And now on the area where I feel guilty, East of the Divide. Trends continue to be down in this area. I gave serious thought to canceling the advisories for the Wind River Basin and Lander foothills. However, I am holding off now for a few reasons. For one, guidance is indicating some instability, with up to 250 J/Kg of CAPE this afternoon with lifted indices as low as minus 1. In addition, the area will be under the right rear quadrant of the jet this evening. This could lead to some snow squalls as the front moves through the area this afternoon and evening. The other is a feature I saw on the GFS early this morning. There is the presence of a weak 700 millibar circulation around midnight tonight near the Natrona / Fremont County border, giving a decent amount of QPF (as much as a a quarter of an inch). If this further moves a bit further west, it could impact Riverton and Lander. Eastern portions of the basin still have a 1 in 2 chance of 3 inches of snow as well. So, we will leave them up for now. Highlights still look good for Johnson and Natrona Counties though, with most probabilistic guidance giving at least a 1 in 2 chance of 3 inches of snow or more. In this area, the highest impact will be Thursday night. Wind will also be an issue, especially in the favored northwest flow / cold advection locations, like Johnson County and the Bighorn Basin, bring blowing snow and more impacts with gusts over 40 mph at times later this afternoon and evening.

Conditions should begin to improve on Friday as the trough and front move away to the east. Unstable northwest flow and cyclonic curvature will keep snow showers going through much of the day. Then we turn to Friday night with the potential for a freeze. As I have stated before, the concern is not with crops and gardens as Wyoming residents know not to plant this early. The main concern will be for flower gardens, trees and sprinkler systems. The variables remain the same. First, if it can clear out enough. Chances are better for this across the north and west, with decreasing chances further south. The other is snow cover, chances of lows below 20 have decreased somewhat across the Bighorn Basin and Wind River Basin with the smaller amounts of snow reducing albedo. Probabilistic guidance still gives a greater than 2 in 3 chance of lows below 25 across almost all the area though. We will hold off on any freeze products with the greater concern of the snow but some will likely be needed.

The remainder of the forecast period looks largely tranquil as ridging builds back over the Rockies for this weekend and early next week. Temperatures will begin to moderate Saturday and likely return to near to above normal levels by Sunday for most. Most areas look dry and warm from Monday through at least Wednesday. The next system is the form of an upper level low may then approach for later next week with the next chance of moisture but these are very fickle this far out so details are still highly uncertain.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 345 PM MDT Thu Apr 16 2026

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals

Lingering snow showers at JAC through 06Z but with low confidence with the southwest flow keeping much of the activity out of the Hole. All other locations dry with windy conditions starting to diminish to 10kts after 02-03Z towards sunset with radiational cooling. However, RKS will remain elevated but not as strong before increasing once again after 13Z. The other TAF sites will gust after 16-18Z with daytime heating and mixing to the surface remaining through the end of the period. Mountain obscuration expected to improve by Friday morning as the system pivots eastward.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

Best chances for snow showers will be at CPR after 01Z and overnight as COD chances diminish as much of the activity will remain east. Otherwise, the backside of the low should affect LND/RIW between 08-12Z for a couple hours at each but confidence low carrying PROB30 groups at this time. Any lingering showers/low ceilings will lift by Friday morning to the mid levels as winds increase once again with daytime heating after 17-19Z. Mountain obscuration will remain overnight improving after sunrise Friday morning.

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 Storm Warning until 6 AM MDT Friday for WYZ001-002-012.

Freeze Warning from 9 PM this evening to 9 AM MDT Saturday for WYZ003>006-017-018.

Winter Weather Advisory until 6 AM MDT Friday for WYZ008>011.

Winter Storm Warning until 6 PM MDT Friday for WYZ014-015.

Winter Weather Advisory until noon MDT Friday for WYZ019-020- 022.