textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Strong winds gusting 40 to 50 mph today across much of western Montana and north-central Idaho.

- 70 percent chance for winds briefly exceeding 50 mph in the Pinesdale area of the western Bitterroot Valley, 85 percent chance in Anaconda later today. Isolated tree damage possible.

- Moderate heat risk in the lower valleys of north-central Idaho as highs could reach upper 90s to low 100s Friday.

- Surge of monsoon moisture could bring showers and thunderstorms capable of heavy rain Friday night into Saturday Lemhi County to southwest Montana.

No significant changes expected today. Strong westerly winds gusting 30 to 45 mph with isolated higher gusts are still on tap across western Montana and Lemhi County. Anticipated impacts include hazardous boating conditions on area lakes, crosswinds affecting high- profile vehicles, and potential tree damage leading to localized power outages. Furthermore, the hot, dry, and windy environment will generate elevated fire weather concerns across southwest Montana.

A weak, dry cold front will advance from north to south across the region this evening, accompanied by broad, modest surface pressure rises after 6 PM MDT. Cold air advection aloft will intensify mid- level, ridge-top winds to near 60 mph across west- central Montana, inducing elevated mountain waves. High-resolution guidance suggests the strongest downward momentum will likely remain above the valley floors, hindered by a developing stable nocturnal layer and a lack of precipitation or virga to facilitate downward momentum transport. However, localized severe gusts remain possible. Concurrently, isolated showers and thunderstorms may initiate over the Continental Divide in Glacier National Park, posing localized threats of lightning, small hail, and gusty outflow winds.

Wednesday will bring temperatures 5 to 10 degrees cooler, returning the region to near-seasonal normals. The departing shortwave will focus scattered showers and thunderstorms across northwest Montana along the Continental Divide, while the remainder of the region stays dry. Upper level ridging will amplify Thursday and Friday, driving temperatures back to or slightly above Tuesday's values. Lower valleys in north-central Idaho are forecast to reach the low 100s by Friday, carrying an 80 percent probability of reaching Moderate HeatRisk and posing a threat to vulnerable populations lacking adequate cooling or hydration.

Another upper-level disturbance will approach late Friday into Saturday, reintroducing wind and precipitation chances. Thunderstorm probabilities will increase by Saturday, particularly along and south of the Interstate 90 corridor.

AVIATION

Strong westerly winds are expected to develop after 16/1800Z/1200MDT today. Sustained winds of 15 to 25 kts and gusts reaching 40kts will be possible in the afternoon, through 17/0000Z/1800MDT. Isolated showers and thunderstorms will be possible in the terrain along the Continental Divide from 16/2200Z/1500MDT to 17/0300Z/2100MDT. The convection will be capable of mixing down strong and erratic winds, and small hail.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Wind Advisory from 1 PM this afternoon to 10 PM MDT this evening for Flathead/Mission Valleys...Kootenai/Cabinet Region... Lower Clark Fork Region...Missoula/Bitterroot Valleys... Potomac/Seeley Lake Region...West Glacier Region.

Wind Advisory from 1 PM this afternoon to midnight MDT tonight for Bitterroot/Sapphire Mountains...Butte/Blackfoot Region.

ID...Wind Advisory from 1 PM this afternoon to 10 PM MDT this evening for Eastern Lemhi County...Western Lemhi County.