Issued Sunday May 11, 2025 7:55 P.M. MDT

* STRONG TO LOCALLY SEVERE THUNDERSTORMS POSSIBLE SUNDAY EVENING *

Tonight…Showers and thunderstorms likely this evening then showers and isolated thunderstorms overnight. Some thunderstorms may be severe with large hail, damaging winds and frequent lightning. Areas of fog developing towards dawn. Lows in the 40s with upper 30s around 5000 feet. Light wind except strong gusty winds possible near thunderstorms. Ridge top winds west 15 to 25 mph with gusts to 30 mph developing after midnight.

Monday…Areas of fog and low clouds through mid morning otherwise variable cloudiness with scattered to numerous showers and thunderstorms in the afternoon. Snow level lowering to near 6000 feet. Local snow accumulations of 1 to 3 inches possible above 6500 feet. Thunderstorms may contain heavy rain, small hail and gusty winds. Highs in the upper 50s to mid 60s with lower 40s around 5000 feet. Southwest winds 10 to 20 mph with ridge top winds west to southwest 15 to 30 mph. Stronger gusts possible near thunderstorms.

Monday night…Variable cloudiness with isolated to widely scattered showers developing overnight. Snow level near 5500 to 6000 feet. Lows in the mid 30s to mid 40s with upper 30s around 5000 feet. Light wind except local gusty west to southwest winds 10 to 20 mph through favored canyons and along portions of Lake Koocanusa. Ridge top winds southwest 15 to 25 mph.

Tuesday…Rain and mountain snow showers likely from Trout Creek to Happys Inn north with scattered showers and isolated afternoon thunderstorms south of Trout Creek to Happys Inn. Snow level near 6000 feet. Snow accumulations of 1 to 2 inches possible above 6500 feet. Highs in the mid 50s to mid 60s with lower 40s around 5000 feet. West to southwest winds 5 to 15 mph.

EXTENDED OUTLOOK (WEDNESDAY THROUGH SUNDAY):

Wednesday…A chance of showers and thunderstorms with a chance of mountain snow showers. Lows in the mid 30s to mid 40s with upper 30s around 5000 feet. Highs in the mid 50s to mid 60s with lower 40s around 5000 feet.

Thursday…Mainly dry except for a slight chance of late day showers along the Idaho border. Lows in the mid 30s to mid 40s with upper 30s around 5000 feet. Highs in the upper 50s to upper 60s with upper 40s around 5000 feet.

Friday through Sunday…Unsettled and cool with a chance of valley rain showers and mountain snow showers. A slight chance of thunderstorms. Lows in the upper 30s to mid 40s with upper 30s around 5000 feet. Highs in the 60s with mid 40s around 5000 feet.

In-Depth Weather Discussion for Northwest Montana/North Idaho/Northern Rockies

ISSUED 05/11/2025 8:20 P.M. MDT/7:20 P.M. PDT

SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY):

After a good rainfall in the morning across North Idaho another shortwave is rotating into the region as of this writing on Sunday evening. This feature is associated with some good upper level jet dynamics as well as a good convergence/divergence couplet located across Northwest Montana. As of 8:00 pm.m MDT/7:00 p.m. PDT there was a radar indicated severe thunderstorm that moved across northwest Sanders County with reflectivity showing ping pong ball sized hail and 60 mph wind gusts. Have not heard of any reports of damage but the most intense part of this storm appeared to located over very rural parts of Sanders County west of Noxon and south of Heron along the Idaho line and up in the Coeur d’ Alene Mountains. Instability will remain present throughout the evening hours as the incoming shortwave helps to provide the needed lift or vertical motion through the atmosphere to generate precipitation, some of which will be locally intense. Largely this will be beneficial rainfall and even some high elevation snowfall as well with our region coming off a largely dry April. The shortwave will lift north into southern Canada with a trowal feature developing around the system which looks to provide another round of beneficial rains and high elevation snowfall into Tuesday for at least parts of the region although the exact location continues to change with each model run. Outside of this feature will be a smattering of showers and thunderstorms but thunderstorms will not be strong to severe outside of Sunday evenings potential. Instability will be present and any passing shortwave within the flow will help provide additional support to generate convection. Temperatures will actually remain below average for a few days and potentially the entire week as a progressive and fairly flat flow remains in place across our region with cooler atmospheric height and thickness values remaining in place. With the upcoming weekend featuring several notable events weather will be playing a large role. Read below for more details.

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY):

Lingering instability and another passing shortwave disturbance on Wednesday will provide for additional sunshine and scattered heavy, possibly thundery downpours. There is decent confidence that a transitory shortwave upper level ridge will pass overhead sometime late Wednesday night into late Thursday afternoon offering up a stable airmass with more sunshine but an active North Pacific jet stream associated with a negative height anomaly in the Gulf of Alaska will be directing yet another strong shortwave passage into the region on Friday and lasting through the weekend. This feature will also have some decent jet support for this time of year so it looks like at least periodic rounds of rain and high elevation snowfall from Friday and lasting through the weekend. The Lost in the 50s event in Sandpoint is next weekend and it looks wet for that event as well as cool. In addition there is the annual Eagle Valley Auction over by the Libby airport which also looks a bit damp and cool. Finally and not to be missed is the “Fishmas” opener in Northwest Montana as the stream fishing opener takes place. If planning on casting a line in the water for this take the jacket and rain coat as it will likely be very cool and damp especially Saturday morning. The overall trend is for the active North Pacific jet to remain focused across our region bringing typical May weather to the Northern Rockies with periodic rounds of valley rain showers and higher elevation snow showers. After the dry April the precipitation will definitely be welcome to gardeners and farmers alike although the timing may not be the best.