Area Forecast Discussion

KEY MESSAGES

- Isolated to widely scattered showers and thunderstorms become more common between by 2 PM Sunday. The best chance for the showers and storms remains over the north-half of the state where a few storms could be strong (wind gusts around 50 mph). - Sunday stays unseasonably hot with daytime highs in the 90s to lower 100s. A Heat Advisory continues through 9 PM Sunday for lower elevations east of the Continental Divide.

- Moisture from the southwest continues to stream northward into Wyoming through at least Wednesday, allowing for little change in the cadence of afternoon and evening showers and thunderstorms. Temperatures remain above normal.

UPDATE

Issued at 1222 PM MDT Sun Jul 26 2026

Moisture continues to spread northward across Wyoming as it rotates around high pressure anchored over the southern Rockies. There is little, if any, change in this pattern over the next several days. A shortwave within this southwest flow aloft will track across southern Montana Sunday afternoon and evening. Scattered showers and thunderstorms erupt across mainly northern Wyoming by 2 PM Sunday and progress east through the afternoon. Many locations will see a downturn in convective coverage by 7 PM Sunday, while locations over north-central Wyoming see the convection linger until 9-10 PM Sunday. Latest 18Z KRIW sounding shows 0.81" of precipitable water, well-above average, but much of it is concentrated above 550mb. Therefore, as we saw Saturday, brief downpours are possible with the thunderstorms. However, again given high-based convection and a dry sub-cloud layer, the primary hazard will be gusty outflow wind 40 to 50 mph. SPC has our northern-tier of counties highlighted within a marginal risk for severe wind gusts. A secondary shortwave works its way north from Utah Sunday evening and overnight leading to intermittent light showers across the far south and eventually western portions of the forecast area through sunrise Monday. Increased mid/high-level cloud cover associated with this wave should help drop Monday highs a few degrees, while possibly delaying the onset of scattered showers and thunderstorms until closer to mid-afternoon Monday.

DISCUSSION

Issued at 249 AM MDT Sun Jul 26 2026

The overall pattern across the western US remains relatively unchanged today, with the H5 ridge centered over the Four Corners, and WY along the northern periphery of the ridge. Above normal temperatures remain in place across the state under the ridge, with record to near-record highs again expected today. The Heat Advisory remains in place for the lower elevations of central and northern WY for the continued heat and the very warm overnight temperatures. Monsoon moisture continues to wrap around the northern edge of the ridge into NW WY, which will bring another round of showers and thunderstorms. Storms again will initially form on the higher elevations of the western mountains and move to the northeast. Storms will have good forward motion again, so this will minimize the overall flooding threat. Strong Inverted-V profile indicates main thunderstorm threat will be gusty winds, possibly gusting above 50 mph, especially across northern WY where the T-Td spread will be greatest.

Longer term models show nearly no change in this pattern the entire week, with the H5 ridge holding fast across the Southern Rockies. This will keep the heat in place, with the daytime thunderstorms each afternoon for NW WY. An embedded shortwave races around the northern edge of the ridge on Wednesday, which could bring an enhancement of the thunderstorms for more of the state.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 525 PM MDT Sun Jul 26 2026

A shortwave moving through southern Montana late Sunday afternoon has allowed for scattered showers and thunderstorms, mainly across northern Wyoming. Convective outflow wind gusts 35-45kts remain the primary hazard with almost any shower or thunderstorm before the shortwave moves east by mid-evening. Precipitable water also favors brief heavy downpours and the potential for reduced visibility over a less than 30-minute period. Expect almost all northern convection to wane by 04Z-06Z/Monday. However, areas around KRKS and eventually the other terminals west of the Continental Divide see the moist, southwest flow bring another moisture surge northward Sunday evening and overnight. Scattered light showers with gusty outflow wind around 35kts will be possible into Monday morning in these areas. This moisture then serves as the fuel for another round of diurnal convection beginning around mid- afternoon Monday.

Westerly surface wind 10-20kts at the western terminals fades around 01Z-02Z/Monday. Many terminals see wind less than 10kts, outside of convection, until late Monday afternoon when convective outflows occur.

Please see the Aviation Weather Center and/or CWSU ZLC and ZDV for the latest information on smoke, icing, and turbulence forecasts.

RIW WATCHES / WARNINGS / ADVISORIES

Heat Advisory until 9 PM MDT this evening for WYZ003>006-010- 011-017-018-020.