textproduct: Western and Central Wyoming

KEY MESSAGES

- Warm, dry and windy today, with elevated to critical fire weather conditions.

- Warm on Saturday, with a bit less wind. A few dry showers or thunderstorms are possible, with outflow winds up to 50 mph the main hazard.

- A weather system brings much colder temperatures for Sunday and Monday, along with widespread moisture. Snow is looking very likely for lower elevations, possibly impacting Monday morning travel. Confidence remains low on where the heaviest precipitation falls.

UPDATE

Issued at 1236 PM MDT Fri May 15 2026

The warm, dry, and windy forecast remains on track for today and tomorrow, with no notable adjustments made. Focus remains on the weather system for Sunday and Monday. Like the full discussion mentions, models have trended towards a deeper trough, though there remains uncertainty on where/if the heaviest precipitation falls. Current trends bring better liquid amounts further south than previous model runs, with the Wind River Mountains, South Pass, and east towards Casper being the most favored locations for the greatest totals. For actual liquid amounts, most of the area has a good chance (widespread 40 to 90 percent chances) for moisture, with those aforementioned favored locations having the potential for 0.75 to 1.00 of liquid. Cluster analysis would suggest about a 40 percent chance for higher than currently forecasted values, and about a 30 percent chance for less - again indicating the current uncertainty with this event.

All that said, the main impacts will likely be with snow that falls Sunday night into Monday morning. Initial snow would likely melt, but with sub-freezing temperatures, wet surfaces could freeze, with then accumulating snow on top. The Monday morning commute could be impacted by this. South Pass would be a location of note, with higher snow totals and gusty winds. Furthermore, a strong northerly wind is expected Sunday night with the front. This could further impact travel as snow and blowing wind create lower visibilities across the Bighorn, Wind River, and Powder River Basins, and down into Sweetwater County. Again, there is still some uncertainty with this system, so stay tuned though the weekend for further updates.

DISCUSSION

Issued at 219 AM MDT Fri May 15 2026

May is typically a very volatile month across Wyoming. It is traditionally our wettest month, and can see anything from severe thunderstorms to blizzards, sometimes at the same time. And over the next several days, volatile will be a good way to describe it.

Today looks like more of the same when compared to Thursday. That means another day of above normal temperatures and low humidity. A gusty wind will still be present. However, with the jet moving further north, it should be down a few notches when compared to yesterday. However, gusts over 25 mph are still a greater than 1 out of 2 chance for many locations and as a result, it will be another day of elevated to critical fire weather. No fire weather highlights though because fuels are not critical. And across the border, we can't completely rule out a stray shower. However, the chance is at most 1 out of 10 so we left for forecast dry. And with dew point depressions approaching 60 degrees, they would likely be virga showers. They could produce some wind gusts past 50 mph though if your are one of the people that get caught near one.

Saturday looks like the transition day. Most areas will have one more dry and warm day. There are a couple of exceptions though. One is across southern Wyoming where a bit of energy may bring a couple of showers or thunderstorms. But the second, and more important system, will be an upper level low moving in from the Pacific northwest. It could bring a few showers to northwestern Wyoming, but even there most of the day should be dry with most precipitation holding off until after sunset. With humidity remaining low, elevated fire weather again looks likely across much of the area. However, with somewhat less wind and somewhat higher humidity, concerns might be down a bit when compared to Friday.

Sunday is when things begin to get interesting as the upper level low moves towards Wyoming. Most guidance now shows the low opening up into a fairly deep trough as it crosses the state. Most guidance does show the main impacts from later Sunday through Sunday night into Monday. However, this is where the agreement ends. Some deterministic models, like the GFS, as well as some ensemble members, show a more progressive system that exits by Monday evening and keeps the heaviest precipitation across Colorado. Other ensemble members, as well as the European model, have a slower and wetter system (which is badly needed given the current drought). However, even it has shifted a bit further south and east with the heaviest precipitation. So, what we are saying is that although most areas should see some precipitation, amounts and placement of the heaviest is still very much in flux. However, one thing we have fairly good confidence in is that much of it will be in the form of snow, even in the lower elevations. Largely rain will fall during the day on Sunday. However, as cold air gets pulled in , 700 millibar temperatures will fall to minus 6 celsius or less, dropping snow levels to the valley and basin floors. The National Blend of Models Ensemble shows at least a 2 out of 3 chance of an inch or snow across most of the area for the 48 hours ending at 6 pm Monday, with the exception of the Bighorn Basin. As snowfall amounts go up, things become very elevation dependent, as would be expected in mid May. The greater than 1 in 2 chance of 3 inches of snow or more is largely restricted to locations above 5500 feet or so. The greater than 1 in 2 chance of 6 inches or more is largely restricted to the mountains. There is a greater than 1 in 2 chance of over a foot of snow across the higher elevations of the Wind River Range and Bighorns though. One thing to note, the official snow will probably not be what people see in their yards. The warm ground will melt some of the snow on contact and a lot of the snow that falls during the day on Monday will have trouble sticking with the very high mid May sun angle. Temperatures will be below normal starting Sunday and especially into Monday.

On Tuesday a second system may impact the area, especially the west, but this one has less moisture to work with. Cyclonic curvature will linger over the area into Wednesday, keeping temperatures below normal and a few showers in the forecast. More zonal flow returns for the end of next week, bringing a drier and warmer pattern.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1145 AM MDT Fri May 15 2026

VFR conditions are forecast over the next 24 hours. Winds are likely to be the most impactful aviation-related weather today with many sites seeing gusts in the 20 to 30 kt range. No precipitation is in the forecast for TAF sites, but COD could see a few isolated late afternoon showers to the northwest, while RKS could see scattered showers to the southeast. Apart from these two TAF sites, western and central Wyoming will see mostly clear skies, save for a few thin high cirrus clouds.

Winds decrease quickly around sunset. Saturday will bring increased high and mid-level cloud cover ahead of the next weather system, with a 10 to 20% chance of brief afternoon showers for most airports.

FIRE WEATHER

Issued at 219 AM MDT Fri May 15 2026

It will be another warm day today with humidity falling under 15 percent for many locations. Wind will be somewhat lighter than yesterday. However, with a greater than 1 out of 2 chance of wind gusts over 25 mph across much of the area, elevated to critical fire weather will occur this afternoon. There should be some improvement Saturday with somewhat higher humidity and less wind. Much cooler and potentially wetter weather moves in for Sunday and continues into early next week.

RIW WATCHES/WARNINGS/ADVISORIES

None.