Northwest Montana Regional Forecast

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

Issued Monday June 24, 2019 - 10:35 p.m.

Monday night…Variable clouds in the evening with a slight chance of showers or thunderstorms north and west of Troy then clearing overnight. Patchy valley fog and low clouds developing towards morning. Lows in the mid 30s to mid 40s with lower 40s around 5000 feet. Light wind.

Tuesday…Patchy early morning valley fog and low clouds otherwise mostly sunny in the morning. Partly cloudy and a little warmer in the afternoon. Highs in the 70s to near 80 with mid 50s around 5000 feet. Afternoon southwest wind 5 to 15 mph.

Tuesday night…Partly cloudy. A slight chance of showers overnight south of Noxon to Happys Inn and west of the Cabinet Mountains. Lows in the 40s to near 50 with mid 40s around 5000 feet. Light wind.

Wednesday…Variable cloudiness. A chance of afternoon and evening showers and thunderstorms. Some thunderstorms may be strong in the late afternoon and evening with very heavy rain, frequent lightning, hail and strong gusty winds. Highs in the lower 70s to lower 80s with upper 50s around 5000 feet. Local east to northeast wind 5 to 15 mph except strong gusty winds near thunderstorms.

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Extended Outlook (Thursday through Monday)

Thursday…Cooler with showers likely and a chance of thunderstorms. Lows in the upper 40s to mid 50s with lower 40s around 5000 feet. Highs in the lower 60s to lower 70s with upper 40s around 5000 feet.

Friday…A chance of showers and thunderstorms. Lows in the 40s all elevations. Highs in the lower 60s to lower 70s with upper 40s around 5000 feet.

Saturday through Monday…Dry and warmer. Lows in the lower 40s to lower 50s. Highs in the 70s Saturday warming to the mid 70s to mid 80s by Monday. Around 5000 feet lows in the lower 40s Saturday morning warming to near 50 by Monday morning. Highs near 50 Saturday warming to near 60 Monday.

In-Depth Weather Discussion for Northwest Montana/Rockies

Issued 06/24/2019 10:55 p.m.

Short term (Monday night through Wednesday):

A little early morning rain gave way to a very pleasant late June day with temperatures running a little below average for late June. After the early morning showers passed through the region along with the shortwave that triggered them conditions became much more stable as the day went on. Even though a few showers and thunderstorms developed this afternoon across the mountains of Northern Washington and North Idaho they rapidly fell apart upon entering far northwest Lincoln County. Conditions will remain too stable on Tuesday for anything more than some fair weather cumulus clouds as warming temperatures at 500 mb (18,000 feet) will cap any vertical development to the cumulus. Heights and thicknesses will continue to rise on Tuesday which will help temperatures rise about 5 degrees over those seen today with warmer valleys likely to see 80 degrees or a degree or two higher. Another cold upper level low will continue to drop south along the west coast from Central BC today to off the Oregon coast on Wednesday before beginning to slowly move inland. This will turn our upper level flow more southerly and more importantly more diffluent. Instability will increase as we go into the late afternoon hours with our region in the favorable northeast quadrant of the upper level low. Shear will also become increasingly favorable along with the low level instability and upper level diffluence which, when combined with ejecting vort maxes or shortwaves in the late afternoon hours will help trigger some significant and organized heavy showers and thunderstorms. Some of these thunderstorms as we go into the evening hours may be strong to locally severe with strong, possibly damaging winds, significant hail, very heavy rainfall and frequent lightning. These showers and storms will move at a good clip to the north so flash flooding is not likely although if storms stall or slow down or possibly train across the same locations, flooding will be possible. the instability looks to last for much of the night especially across Lincoln County so thunderstorms may continue for much of the night with several rounds of thunder and heavy rain possible. At this point, any rain will be very welcome as our region remains unusually dry by Northwest Montana June standards.

Long term (Thursday through Tuesday):

The cold upper level low will slowly begin to move across the region on Thursday with cooler temperatures, high elevation snow showers and lower elevation rains and at least a slight chance of thunder although any thunder on Thursday will be much weaker than that we see on Wednesday night. Friday still looks unstable as the upper low and it’s associated cold air will linger across the region with at least a chance of showers nd slight risk of thunder. There is some speculation about the weekend with the GFS showing lingering instability especially over the northern and western mountains for a chance of afternoon and evening showers while the EC and Canadian show much more stable conditions and therefore dry conditions. For now have gone with the EC and Canadian although if the GFS is right will have to add the chances of showers and thunder back in the outlook. Temperatures will begin to warm once again over the weekend and into the following week with temperatures likely to return to above average levels for late June into early July by early next week.