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 Monday August 20, 2018 - 6:40 p.m.

* Air Quality Alert until further notice *

Monday night...Areas of smoke and haze. Mostly cloudy this evening then clearing and cool overnight. Patchy frost possible in colder valleys. Patchy valley fog possible after midnight across far southern Sanders County south of Thompson Falls. Lows in the upper 30s to upper 40s except locally lower 30s around Yaak, Trego and McGinnis Meadows. Around 5000 feet lows in the upper 40s. Local east wind 10 to 15 mph along the Kootenai River between Troy and Libby and along the Clark Fork River between Heron and Noxon. Ridge top winds east 10 to 20 mph.

Tuesday...Areas of smoke and haze. Patchy early morning valley fog across southern Sanders County south of Thompson Falls otherwise mostly sunny and warmer. Highs in the mid 70s to mid 80s with upper 60s around 5000 feet. Local east to northeast winds 10 to 15 mph with locally stronger gusts possible in the morning between Troy and Libby and between Heron and Noxon. Ridge top winds east 10 to 20 mph decreasing late in the day.

Tuesday night...Areas of smoke and haze becoming more widespread overnight otherwise fair skies. Lows in the 40s to lower 50s with mid 50s around 5000 feet. Light wind. 

Wednesday...Smoke and haze otherwise mostly sunny and warmer. Highs in the upper 70s to near 90 with lower 70s around 5000 feet. Local southwest winds 5 to 10 mph in the afternoon.

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Extended Outlook(Thursday through Monday)

Thursday through Saturday...Occasional cloudiness, locally breezy with a cooling trend but dry. Lows in the 40s to near 50 with lower 50s around 5000 feet Thursday morning cooling to the mid 40s by Friday and Saturday mornings. Highs in the 80s Thursday cooling to the 70s to near 80 Friday and Saturday. Around 5000 feet highs in the upper 60s Thursday cooling to the upper 50s to near 60 Friday and Saturday.

Sunday and Monday...Mostly cloudy, locally breezy and cooler with a chance of showers. Lows in the 40s to near 50 with lower 40s around 5000 feet. Highs in the mid 60s to lower 70s with mid 50s around 5000 feet.

In-Depth Weather Discussion for Northwest Montana/Rockies

Issued 08/20/2018 6:50 p.m.

    What a difference a day makes. Although a considerable amount of smoke remains across the region things have really cleared out nicely and temperatures were much cooler and well below average with all valley locations except for those in the far northwest corner of Lincoln County remaining in the 60s today! An almost 20 degree drop from temperatures on Sunday thanks to the abundance of cloud cover, a cooler air mass and the smoke. Some locations did receive some rain today with the most widespread rains occurring across southern Sanders County and the heaviest rains falling south of Sanders County near Missoula. Clouds have been rather persistent for areas along and east of the Cabinet Mountains due to easterly low level flow. Once those clouds clear out a bit later this evening valley temperatures will drop quickly from the already cool daytime highs we experienced on Monday to potentially some frosty readings in the typical colder valleys like McGinnis Meadows, Yaak and Trego. It's even possible that some areas around Thompson Lakes and locations south of the Libby airport could also see some light frost so keep an eye on the garden. Some patchy valley fog is also possible across valley locations in southern Sanders County that saw some rain earlier today. Our upper level ridge will rebuild once again into our region on Tuesday causing a significant warm up over Monday's cool readings with plenty of sunshine and lighter winds than those experienced on Monday. All valley areas will warm up into the mid 70s to mid 80s or about 15 to 20 degrees warmer than those experienced on Monday. Winds will still be easterly but mainly in the 10 to 15 mph range. The upper level ridge will peak in strength on Wednesday before beginning to flatten out on Thursday which will start the beginnings of a potential major pattern change. A strong upper level trough will begin to develop off the British Columbia coastline lowering heights and thicknesses across our region which will translate into cooler temperatures and more cloud cover along with locally breezy conditions with perhaps some strong winds at ridge top level. Initially this incoming trough will be dry but as reinforcing shortwaves continue to slide into the trough position the chances of rain will increase. Have not gone as bullish with the chances of precipitation yet as we have seen this happen several times this summer only to be disappointed closer to the actual event. Still both the GFS and EC show some precipitation for our entire region on Sunday and Monday so have included a chance of showers for the entire area for both Sunday and Monday. If the wetter GFS pans out then temperatures will have to be lowered further as an abundance of clouds and showers would likely hold temperatures in the 60s in the valleys. Stay tuned.