textproduct: Western and Central Wyoming

KEY MESSAGES

- A few showers are still possible around Buffalo and around Casper Mountain this evening. Any precip will continue have difficulty even reaching the ground.

- An approaching disturbance looks to bring widespread chances for showers and thunderstorms over the weekend. The best chances for a wetting rain remain over the northern half of the forecast area.

- The first week of summer is looking warm with daily chances for showers and thunderstorms.

UPDATE

Issued at 1212 PM MDT Fri Jun 19 2026

The forecast remains mostly on track for the rest of the day today. The main focus turns to the upcoming weekend where chances for showers and thunderstorms return to the region. As mentioned in the previous discussion, an initial push of showers will work its way across the state Saturday morning. Currently, CAMs are showing this boundary stall over portions of Natrona, Johnson Counties and possibly the eastern Bighorn Basin. Locations ahead of this boundary will see increased moisture with dewpoints reaching the upper 40s to low 50s, while those behind it remain drier. The location of this boundary will be key in determining where the best instability will develop. Another caveat will be how much sunshine can break through lingering cloud cover during the late morning and early afternoon Saturday.

Overall, there looks to be widespread chances (20-40% for southern WY and 30-70% for central and northern WY) for showers and thunderstorms throughout the day Saturday. The first push arrives in the early morning hours Saturday and will likely be in the form of light showers with maybe an isolated rumble of thunder. A brief break is expected by the late morning and early afternoon hours, where some sunshine should be able to break through decreasing cloud cover. The early afternoon will see convection begin to initiate off the higher elevations and gradually spread east/northeast. The main concern for the majority of the forecast area will be strong gusty outflow winds and frequent lightning. Hi-res models do indicate strong outflows possibly in excess of 50 mph spreading across the forecast area through the afternoon hours Saturday. Dry thunderstorms and virga showers will be possible, especially across southern WY where the atmosphere looks to be drier. However, locations ahead of the boundary may see some strong storms develop. The favored locations would be Johnson and Natrona Counties where the greatest instability looks to be. That being said, a strong storm or two cannot be ruled out across portions of the Wind River and the Bighorn Basins. As for Johnson and Natrona Counties, strong gusty outflows in excess of 50 mph, frequent lightning, periods of moderate rain and small hail look to be the main hazards in association with any strong storms that do develop. Storms should weaken or move out of the forecast area by sunset. A few lingering showers will be possible mainly over central and northern WY through the overnight hours into Sunday morning.

DISCUSSION

Issued at 230 AM MDT Fri Jun 19 2026

A ridge will build over the region from the west today, as Pacific moisture begins to enter the region. Highs this afternoon will be in the 70s and 80s, with readings approaching the 90 degree mark over the western half of Sweetwater County. Winds will not be as strong today as the sfc pressure gradient loosens and the ridge axis shifts over the Cowboy State. West winds, with gusts up to 25 mph, will develop over areas west of the Divide by mid-afternoon and decrease in the evening. At the same time, another surge of easterly winds will occur over Natrona County into the Wind River Basin, with gusts of 25 to 35 mph occurring through 08Z. Elevated to critical fire weather conditions will also return across southern portions of the forecast area, due to the aforementioned winds and humidity values as low as 8%. Virga showers will be possible across the CWA through the afternoon into the early evening. Brief gusts of 50 to 60 mph could occur from these showers, due to the large dewpoint spreads that will be present. Another area of virga showers will develop over far western portions after 06Z Saturday, moving east of the Divide by the predawn hours Saturday morning. This will be a precursor to the more widespread convective activity expected during the day Saturday.

Chances for precipitation return for the weekend, as a remnant Pacific low moves over the region. Northern portions of the CWA continue to have the best chances to receive any precipitation, with forecasted rainfall amounts trending downwards again (no surprise). Amounts are now in the 0.20" to 0.40" range Saturday through Monday, with portions of Natrona County trending above 0.10". Locally heavy rain remains possible from these storms, as precipitable water values of 0.60" to 1" are still forecasted. Precipitation chances linger into Monday, as a Canadian cold front moves over areas east of the Divide. Dry conditions return to the region Tuesday, as a strong area of high pressure develops over the Desert Southwest. Models remain split whether shortwaves will move over the PACNW/Northern Rockies from Wednesday to Friday, keeping precipitation chances up and the ridge suppressed to the south. Given the latest CPC outlooks of a 33% chance for above normal precipitation, confidence is low to medium at this time.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 349 PM MDT Fri Jun 19 2026

VFR conditions prevail through the next 24 hours, though showers and thunderstorms Saturday afternoon may bring brief MVFR to possibly IFR conditions if moderate to heavy rain occurs. Gusty winds from this afternoon generally decrease through the evening. An easterly push of wind brings gusts 15 to 25 knots at KCPR and KRIW through about 08z. A passage of very light showers and virga showers occur though 12z tonight, moving from the southwest to northeast during those 12 hours or so. Gusty outflow winds are possible, but generally no impacts are expected; KRKS would be the most likely to see impacts, if any. Showers and thunderstorms become widespread starting around 18z Saturday, with chances through the the end of the TAF period. Variable gusty outflow winds 40 to 50 knots is the most likely hazard, though small hail is also possible, mainly around KCPR.

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.