textproduct: Western and Central Wyoming

KEY MESSAGES

- A cool and unsettled day today with periods of showers and isolated thunderstorms, with the most numerous in the afternoon and evening.

- Near to below freezing temperatures are looking likely across the Bighorn Basin tonight into Monday morning. Winds will be gusty at times Sunday evening into the morning hours Monday mainly across southern WY and from Rock Springs to Casper.

- The chance of showers lingers through at least Wednesday and possibly through Friday. At this point, Tuesday night or Wednesday look to have the most numerous showers.

- Snow is possible at the higher elevations. Snow levels remain relatively high through Monday. The main concern for snow at pass level will be later Tuesday through Wednesday as snow levels drop.

UPDATE

Issued at 1058 AM MDT Sun Oct 11 2026

For the most part not much to add regarding the near term with the previous discussions forecast seeing little change. As for the rest of today, cooler temperatures have moved into much of the area. Highs are forecast to be in the low to mid 40s across northern WY with highs in the mid to upper 50s for central WY and temperatures in the low 60s for the south. Winds gradually increase this afternoon mainly across southern WY and along the Wind Corridor from Rock Springs to Casper. Winds will be 25 to 35 mph with gusts up to 65 mph possible at times. As a result, High Wind Watches have been upgraded to warnings and the warnings have also been extended west up to the border of Unita County. The timing of these winds have moved up slightly also, so all wind highlights will begin at 21Z (1500 LT) Sunday through 12Z (0600 LT) Monday. The one other slight adjustment to the forecast was the addition of Freeze Warnings for all the low elevation zones of Bighorn Basin. Model guidance shows much of the Bighorn Basin having a 40-70% of seeing low temperatures of 32F or less. There is the possibility for some locations to see lows drop into the upper 20s. Northern Johnson County was borderline for a Freeze Warning but due to gusty winds any highlights have been held off for right now. That being said preparing for a possible freeze might not be a bad idea for those in northern Johnson County. Otherwise, at least in regards to the near term forecast not much else has changed. An unsettled stretch of weather still is looking possible for much of the upcoming week.

DISCUSSION

Issued at 242 AM MDT Sun Oct 11 2026

It still looks like a rather active several days across the area. And like last night, we have some things we are fairly high confidence in and others that have more uncertainty. We will go over these below, that is why you read the discussion, of course.

Areas of showers are moving across portions of the state as I write this after midnight, with the greatest concentration of them largely across the northern half of the state. These will continue through the night as cold air over runs a cold front that has now slid down to around the Continental Divide (it went through Riverton not long ago, our wind switched to the north and the temperature dropped around 10 degrees). We will continue to showers on and off through the day, with the best coverage once again across western Wyoming. Overall, coverage of showers still looks to be the greatest today as we see the maximum impacts of the moisture streaming northward from the remnants of Tropical Storm Rachel. Overall reasoning looks similar to yesterday, with most numerous showers likely later today and into tonight as the deepest moisture moves toward the area. The deepest moisture still looks to remain west of Wyoming over eastern Idaho, but it will get close to the area. We continue to have a marginal risk of excessive rainfall across the area, this looks reasonable as there will be locally heavy rainfall. And, we have another concern this morning. Some subsidence with a possibly dry slot may develop from Sweetwater through Casper. Most models are showing 50 to 60 knots of wind at 700 millibars. The NBM ensemble gives a greater than 1 out of 2 chance of wind gusts past 55 mph across this area as well. With this we have hoisted a high wind watch from eastern Sweetwater County through Natrona County, although the best chance of high wind in Natrona County would be in western Natrona, not near Casper. Wind should decrease as the subsidence decreases toward sunrise. And, there will likely be some snow in the higher elevations, I will discuss this later in the discussion as well as rainfall amounts.

As we head into Monday, this looks to be a bit of a lull as the deeper moisture from Rachel moves away to the north and east. This is when the dominant feature becomes an upper level low that will move out of the Pacific northwest and into the Great Basin. This is where the uncertainty begins to increase. Some deterministic models as well as some ensemble members keep the low further south, dropping it further south toward southern Utah as well as Colorado. This would keep the greatest forcing and moisture further south, and any showers largely confined to southern Wyoming. The European and some other ensemble members are further north, taking the upper level low closer to the Wyoming-Colorado border which would spread better chances of showers further northward. The current forecast is somewhere in the middle, keeping most showers West of the Divide through day, then pushing deeper moisture further northward on Monday night This will be a cool day as well, with below normal temperatures across most of the area.

Tuesday looks similar, as we may be somewhat of a lull in the showers, with most activity confined to southern Wyoming. By Tuesday night, details become more uncertain. Like yesterday, the GFS remains the faster model, with the low being moved to the east, with all precipitation ending by Wednesday night. The European and some other ensemble members continue to show the upper level low cutting off the upper level low and keeping unsettled weather around through most of the week. There will likely (greater than a 2 out of 3 chance) of an area of steady precipitation across central Wyoming as a period of east to northeasterly upslope flow develops. There are still differences on exactly when this will occur (anytime from Tuesday night through Wednesday night) and the exact position of the heaviest precipitation. The chance is definitely there though. Some, we continue to be confident of a cooler and unsettled pattern. However, confidence in the details remains rather low, especially from Tuesday and beyond.

PRECIPITATION AMOUNTS...I will divide this into two periods. This first through tonight with the moisture from Rachel, and then in the period following that. Most ensemble guidance continues to show the heaviest rain across the western mountains and higher elevations, with lesser amounts further south and east. The area generally north and west of a Kemmerer to Buffalo line has at least a 1 out of 2 chance of a quarter inch of QPF or more, with most falling this afternoon and evening. The chance of an inch or more is largely restricted to the western mountains and a few adjacent valleys. The two areas with the heaviest precipitation (a greater than 1 in 2 chance of an inch and a half or more) are largely across the Wind River Range and western Yellowstone. From Monday morning through Wednesday morning, there is a north to south gradient, with the highest amounts in southern Wyoming, with lesser amounts further north and west. The 1 in 2 chance line of a quarter inch of rain or greater runs south of a Buffalo to Worland to Jackson line. The chance of inch or greater is largely in two locations, far southwestern Wyoming as well as the Wind River Range and also the southern Wind River Basin where there could be that upslope component I talked about earlier in the discussion. Additional precipitation will fall after this, but there is more uncertainty at this time.

SNOWFALL AMOUNTS...We will also talk about two different periods here. For the next 24 hours or so, two areas have the concern. One is over the Absarokas, where 700 millibar temperatures falling to around minus 2 or so, snow levels could fall down to 7000 to 7500 feet. The main concern here is that this may occur after the best moisture has moved away. The chance of 3 inches or more is generally less than 1 out of 3. The exception is near the Beartooth Highway but that is closed for the season. The other is in the Wind River Range. There is decent area of at least a 1 out of 2 chance of 6 inches or more. However, this is only at the higher elevations (above 10000 feet), so impacts will be minimal. The highest peaks may see more than a foot of new snow, but with limited impacts we decided not to issue any highlights. The second period is from Monday morning through Thursday morning. There are more concerns here. Cooler air will move on this day, with 700 millibar temperatures falling to minus 2 to minus 3 across a decent portion of the area, which would drop snow levels to 7000 to 7500 feet. This would put snow levels to pass level, especially on Tuesday night into Wednesday. There is around 1 in 3 chance of 3 inches or more of snow over some passes, like South Pass, Togwotee Pass and South Pass. There is also a much more widespread area of 6 inches of more across the Wind River Range. This looks to be the best chance of highlights, especially for the Wind River Range from Tuesday night to Wednesday. The lower elevations still look to see little or no snow. The areas of main concern are places like Cody tonight and Dubois Tuesday and into Wednesday. There could be a quick accumulation if there is enough dynamic cooling, but the chance is small, generally less than 1 out of 3.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1121 AM MDT Sun Oct 11 2026

Precipitation continue to sweep across western WY this afternoon, with low cigs and vis for all sites except KCPR and KRKS. Except cigs to hover around 1000 feet for northwestern sites, and between 2000 and 3000 or KLND/KRIW. KCPR and KRKS will see some drying this afternoon, with some lifting through the afternoon. Showers will taper off this evening for sites east of the Divide, while another round of light rain returns for western sites tonight into Monday.

Most northern sites will see light winds continue tonight into the day Monday. KBPI/KPNA/KRKS/KCPR will see strong winds develop later this afternoon. Expect gusts of 20 to 25kts at KBPI/KPNA and 40kts at KRKS/KCPR. Winds will taper off Monday morning, except for KCPR, which will see the gusty winds likely continue through 18Z.

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

Freeze Warning from 11 PM this evening to 9 AM MDT Monday for WYZ003>006.

High Wind Warning from 3 PM this afternoon to 6 AM MDT Monday for WYZ019-020-028>030.