textproduct: Western and Central Wyoming

KEY MESSAGES

- A Pacific weather system will cross the area through Tuesday morning and bring rain and snow to much of the area.

- Dry and mild weather returns from Tuesday afternoon through Wednesday.

- A more substantial system brings the chance of snow to much of the area Thursday into Friday, details are still uncertain.

DISCUSSION

Issued at 249 AM MST Mon Mar 2 2026

We are now in a time of transition. First, we have transitioned into meteorological Spring, which began on Sunday. And, we are transitioning into a wetter pattern with a couple of systems expected to bring chances of some needed precipitation. Something we will not be transitioning into are below normal temperatures, as flow will continue to be generally westerly, keeping temperatures largely near to above normal, although there should be some cooling toward the end of the week. Transitions are also the most difficult to forecast, and known to give meteorologists thinning hair and upset stomachs trying to figure out what will happen. And this forecast is no exception.

West of the Divide...We currently have a Pacific front and trough approaching western Wyoming and bringing some rain and snow to those locations. The 700 millibar temperatures are currently running anywhere from minus 4 in the north to minus 2 in the south, putting snow levels between 6500 to 7500 feet. And this is the first forecast problem. How much snow will fall in the valleys. There could be some slight cooling through the day, but for the most part temperatures should be steady, keeping most everything for the valleys a rain and snow mix except the northern Jackson Valley. A lot may depend on precipitation rates where evaporative cooling may overcome this. However, any snow in the valley should have little impact given the ground is fairly warm and the higher March sun angle may melt snow on roads. Cooler air does come in behind the front tonight but the best moisture will have shifted eastward at this point. As for the mountains, there will be some accumulating snow. As for highlights, we decided against them this morning. There are some locations that have a greater than 1 out of 2 chance of 6 inches or more of snow, mainly over the Wind River Range and Salt and Wyoming Range. However, these are largely at the highest elevations and away from the passes. South Pass, Togwotee and Salt Passes all have less than 1 in 5 chance of 6 inches of snow, so impacts would be limited. There is another concern for tonight though. And with some instability in the atmosphere, there could even be a few thunderstorms, another sign of the transition into Spring. Colder air will move in tonight across Sweetwater County, dropping snow levels to 6000 to 7000 feet by midnight. Most guidance also show the area in the left front quadrant of a jet streak, enhancing upward motion. The chance of greater than 3 inches of snow is less than 1 out of 10 except in the sparsely populated far southern areas of the county though. Also, there is not a ton of wind with the system. This may be handled better with short term forecasts or messaging. Precipitation should taper off through Tuesday morning and end by Tuesday afternoon.

High pressure should then bring dry and mild weather from later Tuesday into Wednesday before the next system approaches from the west. And no surprise, guidance has slowed somewhat. The current forecast is probably the fastest it would be. It would not surprise me if Wednesday evening and even much of Wednesday night ended up mainly dry. The main impacts would be Thursday as the front moves through. The air is somewhat colder with this system so much of the precipitation should be snow. Some highlights look more likely with this system, with a greater than 1 in 2 chance of 6 inches or more across the mountain ranges. The greater impact may be East of the Divide though. The main impacts would be over by Friday, with only showers lingering on Friday, followed by drier weather for the weekend.

East of the Divide...Most of the area should start off dry today but chances of showers will increase through the day as the aforementioned Pacific system pushes toward the area. Some showers and yes, maybe a few thunderstorms will be possible this afternoon. However, the bulk of the precipitation will be Monday night. We do know a few things. There will be a south to north gradient with the precipitation, with less as you head north. The heaviest should fall south of the Owl Creek and Bridger ranges toward Casper. There are still some differences in where the heaviest will fall though, and a lot depends on the exact movement of one of those dastardly 700 millibar lows that like to enhance precipitation rates. The current forecast represents the middle ground. All of the areas mentioned in the above have at least a 2 out of 5 chance of a quarter of an inch or more of QPF, with a 1 out of 5 chance of over a half an inch, certainly welcome news given the long dry spell we have had. As for precipitation type, in the lower elevations it would more than likely be just about all rain. The coldest 700 millibar temperatures would drop is around minus 5, which would put snow levels around 6000 feet. This means there could be a small accumulation at times in places like areas west of Lander, along US 20-26 around Hiland on the south side of Casper toward Casper mountain as well as around Dubois. The chance of 3 inches is basically zero now though except for the mountains. So, no highlights but some areas may wake up to a small accumulation of snow Tuesday morning. And one other note, there is a full lunar eclipse late tonight, it starts around 2:30 am and ends at dawn. Unfortunately, most areas will be too cloudy to see it. Areas further north toward Montana, especially the northern Bighorn Basin and Johnson County would have the best chance of catching a glimpse.

All precipitation will end Tuesday morning, with high pressure moving in for Tuesday afternoon through Wednesday night with dry and mild weather expected. The concern for elevated fire weather increases on Wednesday around Casper as gusty southwest wind develops ahead of the next system. However, the rain may mitigate this somewhat. The current forecast is the fastest the next system would move in. We feel many areas could be dry through Thursday morning. Thursday afternoon will likely see more showers developing as the next system moves in. This one is a bit colder though so there could be some snow in the lower elevations with this one, although given the warm start. This does look like a good setup for decent precipitation with lee cyclogenesis over Colorado and low and mid level low turning east to northeasterly, bringing in more moisture and more upslope flow. Guidance still has a fairly decent spread though with the details of the timing and heaviest QPF, so this is still very much in flux. Much of the area has at least a 1 in 2 chance of at least an inch of snow though as 700 millibar temperatures fall to at least minus 8 and make all precipitation snow. The best chance of significant snow is in the favored northeasterly upslope locations right now, generally Lander to Casper and possibly around Thermopolis with the least amounts in the eastern Bighorn Basin. Confidence is low with details though so this will probably change as we head closer to the event. Precipitation should continue into Friday as well. Most guidance then shows drier and warmer weather returning for the weekend.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 420 AM MST Mon Mar 2 2026

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

The next weather system moves across the region during the next 24 hours, with low clouds continuing at all sites. Sites will fluctuate the next couple hours before the next wave moves through, bringing cigs and vis back down to MVFR to IFR for KBPI/KPNA. Low clouds and fog/-sn continue at KJAC through the day, holding at IFR or lower through around 04Z/03, when cigs finally start to lift. KRKS starts VFR this morning, but a round of showers and a possible thunderstorms moves through this afternoon. Lighter rain and lower cigs move in there this evening and likely hold through the rest of the night.

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

This morning will see VFR conditions for all sites with mid clouds. Some very light precip is possible the next couple hours at KCPR, but this moves through quickly. The main push of showers moves into central WY this afternoon, pulling cigs to MVFR at KRIW and IFR at KLND and KCPR, especially after sunset tonight. These sites remain restricted the rest of the overnight hours. A few showers may reach KWRL, but chances are low. KCOD remain VFR with only midlevel clouds and no precip expected.

RIW WATCHES/WARNINGS/ADVISORIES

None.