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.

UPDATE

Issued at 1134 AM MST Mon Mar 2 2026

Things are mostly on track for the next 24 hours. Recent hi-res guidance would suggest that the higher precipitation amounts will be a bit further south compared to before. This lowered precipitation amounts for portions of central Wyoming, like the Wind River Basin into northern Natrona County. Localized higher amounts are possible if showers or thunderstorms this afternoon and evening develop that far north. Any thunderstorms look to mainly occur over the south portions of the area, like Sweetwater County towards Casper. Gusty outflow winds are possible, with gusts 20 to 30 mph, though a gust to 45 mph cannot be ruled out. Rain over Sweetwater County should transition to snow over night. As mentioned in the full discussion, some areas around 3 inches are possible south of I-80, though isolated areas around I-80 could see up to 3 inches, like around Wamsutter.

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 /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1032 AM MST Mon Mar 2 2026

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

A weather system has begun to enter the region which has lead to conditions varying from MVFR to IFR. KJAC looks to see low ceilings of IFR to LIFR conditions linger through the early afternoon with improvement possibly by 23Z Monday. Periods of low ceilings and fog have moved through KPNA and KBPI this morning. Precipitation is expected to move into the area shortly after 20Z with periods of rain and possibly some mixing of rain/snow through 08Z Tuesday. During this time MVFR to IFR conditions will be likely. KRKS will see some showers develop around 21Z however, an isolated thunderstorm or two cannot be ruled out nearby. This may lead to brief period of IFR conditions and some gusty outflow winds of 20 to 30 knots. KPNA and KBPI could see a nearby thunderstorm but at this time most of the convection looks to remain well to the south. As for KRKS, rain continues through 08Z before a possibly transition over to snow or a mix or snow/rain. Precipitation gradually ends through the morning hours Tuesday with KPNA and KBPI seeing precipitation gradually end around 08Z. KRKS sees precipitation linger later into the morning with things moving out by around 13Z Tuesday. Winds remain light at nearly all terminals with a few gusts near 20 knots possible nearby any showers. Mountains will be obscured through most if not all of the period with some improvement possible near the end of the TAF period.

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

A weather system moving into western WY will gradually make its way east by the evening Monday into the early morning hours Tuesday. KLND and KRIW look to see precipitation begin developing around 21-23Z Monday. Prevailing precipitation does not look to arrive until around 03-04Z Tuesday. Temperatures look to warm for snow so most of the precipitation will fall as rain. However, cooler temperatures may make their way into the area by about 07Z which may lead to a brief transition over to a mix of rain/snow through about 11Z. During this time periods of MVFR to IFR conditions will be possible with conditions improving through the rest of the morning on Tuesday. KCPR will see precipitation near around 23Z with some isolated thunderstorms possible nearby through 03Z Tuesday. Some of these storms may produce brief outflow winds of 20 to 30 knots. Showers and light rain remain nearby KCPR through about 11Z Tuesday with conditions improving shortly afterwards. KWRL and KCOD do not have the best chances of seeing any precipitation and as a result of this no precipitation groups have been included in their TAFs. Winds across all terminals look to remain light through much of the period with the only exception being outflow winds nearby any showers or storms. Mountains will be obscured through much of if not all of the period with some improvement possible near the end of the TAF 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

None.