Northwest Montana Regional Forecast

Includes Lincoln and Sanders Counties (cities of Libby, Troy, Eureka, Yaak, Bull Lake, Noxon, Heron, Trout Creek, Thompson Falls, and The Cabinet Mountains)

Issued Sunday August 19, 2018 - 4:40 p.m.

* Air Quality Alert until further notice *

Sunday night...Smoke and haze otherwise becoming mostly cloudy with a chance of showers and thunderstorms developing. Locally dense smoke with visibility down to 1 mile in places. Lows in the mid 40s to lower 50s with near 50 around 5000 feet. Northeast wind 5 to 10 mph except east winds 10 to 20 mph developing along the Kootenai River between Libby and Troy and along the Clark Fork River between Noxon and Heron. Ridge top winds east 15 to 25 mph.

Monday...Smoke and haze otherwise mostly cloudy in the morning with a chance of showers and thunderstorms becoming partly cloudy with isolated showers and thunderstorms in the afternoon, mainly across southern Sanders County. Cooler with highs in the 70s with lower 60s around 5000 feet. Northeast winds 10 to 20 mph with local gusts to 30 mph. Ridge top winds east 15 to 30 mph with local gusts to 40 mph in the morning.

Monday night...Smoke and haze. Partly cloudy in the evening then fair skies and cooler. Patchy frost possible in colder valleys. Lows in the upper 30s to upper 40s with near 50 around 5000 feet. Evening northeast wind 5 to 15 mph becoming light except locally gusty east winds along the Kootenai River between Libby and Troy and along the Clark Fork River between Noxon and Heron along with higher elevations.

Tuesday...Smoke and haze. Mostly sunny and warmer. Patchy early morning frost possible in colder valleys. Highs in the mid 70s to mid 80s with upper 60s around 5000 feet. Northeast wind 5 to 10 mph. 


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Extended Outlook(Wednesday through Sunday)

Wednesday through Saturday...No precipitation. Becoming a little cooler and locally breezy by Friday and Saturday. Lows in the upper 30s to near 50 with mid 50s Wednesday and Thursday cooling to the upper 40s Friday and Saturday around 5000 feet. Highs in the 80s Wednesday and Thursday cooling to the 70s Friday and Saturday. Around 5000 feet highs in the lower 70s Wednesday and Thursday cooling to the upper 50s to near 60 Friday and Saturday.

Sunday...Locally breezy with a slight chance of showers near the Canadian border otherwise dry. Lows in the 40s with upper 40s around 5000 feet. Highs in the 70s to near 80 with near 60 around 5000 feet.


In-Depth Weather Discussion for Northwest Montana/Rockies

Issued 08/19/2018 4:55 p.m.

    Dense smoke moved into much of the region overnight on Saturday and has persisted for much of the day on Sunday which has also helped to keep temperatures down so far to more seasonal readings. Some rather significant changes are beginning to take place in the overall pattern across North America and even the North Pacific which resemble more of an early autumn pattern. The persistent upper level ridge that has once again been incredibly dominant across much of the Western US this summer is showing signs of retrograding a bit off the coast of Washington. This is in response to a shortwave that is dropping southward along the British Columbia and Alberta borders as of this writing. As this shortwave continues to drop southward models indicate that it will strengthen somewhat and provide some additional lift and instability to trigger a few showers and thunderstorms later tonight into Monday morning across our region. There is the outside chance that some more widespread showers could develop especially along the Cabinet Mountains and the Coeur d' Alene Mountains in Sanders County if lift and instability is plentiful enough. This system will also tighten up the easterly gradient across our region which will produce some gusty easterly winds across the higher elevations along with those areas prone to east winds such as along Highway 2 between Troy and Libby along the Kootenai River and along Highway 200 along the Clark Fork River between Noxon and Heron. Smoke may also continue to be rather dense so have included the possibility of dense smoke in the forecast with visibility down to 1 mile or possibly even less. It's not clear yet what effect the gusty winds will have on the smoke but we should see some temporary improvement later tonight into Monday with the east winds. The chance of showers and thunderstorms will clear most of Lincoln County in the morning on Monday but will likely linger across central and southern Sanders County until mid to late afternoon on Monday. These areas have the best shot at possibly seeing some more wetting rains and improved air quality. Winds will calm down some Monday night although higher elevations and those east/west canyons will hold on to locally gusty east winds. Valley temperatures will cool substantially Monday night into Tuesday morning, enough so that some of our colder valleys such as near McGinnis Meadows, around Yaak, Trego and perhaps even Thompson Lakes and the south end of the valley near Libby may see some frost early Tuesday morning so if you live in these areas be prepared to cover your garden if need be. The upper level ridge will shift eastward once again on Tuesday bringing calmer winds and warmer temperatures but also likely more smoke from regional wild fires. The upper level ridge does show signs of being progressive though as a stronger upper level trough begins to slide down the British Columbia coast and Northeast Pacific towards the end of the week which will bring some locally breezy conditions and cooler temperatures by Friday into next weekend. For now conditions look to remain on the drier side with chances of showers being confined mainly to our north which should greatly help with fires in Canada. By Sunday there are some more consistent signs that some added upper level dynamics and lift may begin to approach our side of the border so have introduced a slight chance of showers for far northern Lincoln County near Yaak and Eureka for next Sunday. Hopefully this will be the beginnings of a more widespread and significant change towards cooler and more unsettled conditions to lessen fire danger and improve air quality. Keep checking back often.