Issued Wednesday April 23, 2025 8:35 P.M. MDT
Tonight…Fair skies. Lows in the lower 20s to lower 30s except mid to upper 30s in thermal belts on slopes and hillsides with mid 30s around 5000 feet. Light wind except local east to northeast winds 10 to 15 mph developing after midnight through favored canyons, along portions of Lake Koocanusa and across ridge tops.
Thursday…Mostly sunny and warm. Highs in the lower 60s to lower 70s with lower 50s around 5000 feet. East to northeast winds 5 to 15 mph except local east to northeast winds 10 to 20 mph with gusts to 25 mph through favored canyons, along portions of Lake Koocanusa and across ridge tops.
Thursday night…Fair skies and not as cold. Lows in the upper 20s to upper 30s except lower 40s breezy areas and in thermal belts on slopes and hillsides with upper 30s around 5000 feet. Light wind except local east to northeast winds 10 to 20 mph with gusts to 25 mph through favored canyons, along portions of Lake Koocanusa and across ridge tops.
Friday…Occasional high cloudiness otherwise mostly sunny and warm. Highs in the mid 60s to mid 70s with mid 50s around 5000 feet. Northeast winds 5 to 15 mph except gusty east to northeast winds 15 to 25 mph through favored canyons, along portions of Lake Koocanusa and across ridge tops decreasing in the afternoon.
EXTENDED OUTLOOK (SATURDAY THROUGH WEDNESDAY):
Saturday…Increasing clouds and continued warm. Lows in the mid 30s to mid 40s with mid 40s around 5000 feet. Highs in the mid 60s to mid 70s with upper 50s around 5000 feet.
Sunday through Wednesday…Cooler with a chance of showers and a slight chance of thunderstorms. Lows in the 40s with near 40 around 5000 feet. Highs in the upper 50s to mid 60s with upper 40s around 5000 feet.
In-Depth Weather Discussion for Northwest Montana/North Idaho/Northern Rockies
ISSUED 04/23/2025 9:00 P.M. MDT/8:00 P.M. PDT
SHORT TERM (WEDNESDAY NIGHT THROUGH FRIDAY):
Upper level ridging will remain in place across the region throughout the short-term forecast period. This will mean another night of widespread frost and freezes across valley locations throughout the region for at least one more night. Surface high pressure will begin to slide southeast from British Columbia into southern Alberta and North Central to Northwest Montana. This will create a tightening northeast surface pressure gradient across the region late tonight and peak in strength on Thursday night into early Friday before weakening by Friday afternoon. Winds for most locations will be light northeast but the typical favored regions through the Purcell Trench in North Idaho as well as along portions of Lake Koocanusa, the Highway 2 corridor between Troy and Libby and the Clark Fork River Valley between Noxon and Heron will see the strongest winds and there could be gusts up to 25 mph in these locations as well as across higher elevations especially Thursday night into around noon on Friday. Winds will quickly decrease on Friday afternoon as surface high pressure weakens and slips south. Other than a few high clouds on Friday afternoon skies will remain mainly clear and high temperatures will run around 10 degrees above late April seasonal averages with plenty of upper 60s to mid 70s away from the larger cold lake bodies of Pend Oreille and Priest Lakes. The wind will keep frost restricted Thursday night to the wind sheltered valleys while breezy locations will see low temperatures fairly mild and near 40 degrees.
LONG TERM (FRIDAY NIGHT THROUGH WEDNESDAY):
Not much to talk about in the extended forecast period. Originally it appeared that a colder upper level trough would move into the region this weekend but that system now looks to dive southeast into Northern California and Southern Oregon taking the best lift, dynamics and instability with it. A bit of an inverted trough may stretch northwest from the trough by Sunday which could provide just enough low level convergence at the surface and upper level instability for a few showers but nothing terribly exciting. A new upper level trough looks to approach from the North Pacific by Monday and lasting through Wednesday which will spread cooler temperatures and chances for mainly rain showers with any snow remaining confined to the highest elevations above 7000 feet. With our warmer temperatures mountain snow melt will increase with area creeks and streams as well as larger rivers running fast, swift and cold so be sure to be very careful if traveling outdoors to enjoy the Spring-like weather.