Forecast Discussion

Issued 10/12/2026 7:45 p.m. MDT / 6:45 p.m. PDT

SHORT TERM (MONDAY NIGHT THROUGH WEDNESDAY):       

     After a chilly, unsettled, and in some locations especially across the Purcell Trench in North Idaho very windy second half of the weekend along with all of our mountains seeing their first accumulating snow of the season things have settled down as the surface high responsible for the gusty northeast winds and upslope light snow showers on Sunday in Northwest Montana has shifted further south. This has allowed clear skies and light winds to prevail and will be setting our region up for the coldest night of the season since last March at least across valley locations. Thermal belts on slopes, hillsides and across higher elevations saw their coldest night Sunday night into early Monday morning. Many of our colder Northwest Montana valleys will see temperatures drop into the teens with all other valley locations away from the immediate shorelines of Pend Oreille Lake seeing temperatures well down into the 20s. Pend Oreille Lake's water temperature in hovering in the mid 50s and this will tend to keep areas right along the shoreline near 209 to 30 degrees, still cold just not as cold as areas even a quarter of a mile or more inland. Many lakes and rivers will likely see steam fog develop for a couple of hours either side of sunrise with the cold temperatures and relatively warm water sources and the contrast of the two promoting shallow, localized instability. Can't rule out some patchy freezing fog and low clouds each night and morning especially around Priest Lake and the Kootenai Valley near Libby either as these areas are often the first to develop fog and low clouds under a stable atmosphere. Temperatures will be near seasonal averages on Tuesday before rising a few degrees above average by Wednesday. Will also perhaps see a light southwest breeze pick up Wednesday afternoon with a weak shortwave passage but whether those light breezes surface outside of the highest ridge tops appears unlikely.                                      

LONG TERM (WEDNESDAY NIGHT THROUGH MONDAY): 

     Our next weather maker is already spinning out in the West Pacific as what is now typhoon Koguma is currently sitting well of the coast of Japan and really is not being steered in any direction at the moment. Models appear to be slowly drifting Koguma slowly to the northwest and eventually to the north but unlike it's predecessor Choi-Wan which constructively phased with an upper level trough pushing off the coast of Japan and produced our recent cold and rainy/snowy weather Koguma is expected to destructively phase with the westerlies by around Thursday or possibly even Friday. This will result in the flattening out of the North Pacific jet with models showing a strong east to west zonal North Pacific jet strengthening by next weekend and beginning to plow multiple shortwaves into the Northwest and Northern Rockies. The first one looks to move through around Saturday and exits by early Sunday. This will likely produce only some clouds and increased west to southwesterly breezes. The next system which will be the surface low and associated upper level trough from what was Koguma by this time will move in by Monday bringing more winds from the southwest along with much better chances for valley rain and snow. This time the precipitation will tend to favor North Idaho and those areas of Northwest Montana west of the Cabinet Mountains which is often the case with systems pushing in off the Pacific. A bit too early to say how much precipitation will fall but it looks overall wetter than this weekend's system at least for North Idaho. Further systems are lined up in the zonal jet to follow next week so more typical October-like weather may finally be arriving in the Northern Rockies. 

Issued 10/06/2026 5:50 p.m. MDT / 4:50 p.m. PDT

SHORT TERM (TUESDAY NIGHT THROUGH THURSDAY):       

     Not much going on in the short-term with a fairly strong and persistent upper level ridge continuing to dominate much of the Western US apart from a weak upper level low that brought some showers and thunderstorms to the Sierra and Western Nevada on Monday and has now pushed into Utah and Colorado giving them some showers and thunderstorms as well. For our region the zonal jet remains to our north across Central British Columbia and Alberta with a weak surface high residing across our region bringing us mostly clear skies and light winds with patches of night and morning valley fog and low clouds. This will continue through the remainder of the short-term period. Overnight lows will be near to a touch above seasonal averages except across higher elevations and those locations that are in and above the inversion where overnight lows will be well above average. Daytime high temperatures will continue to run 10 to 15 degrees above average through Thursday. Enjoy this while it lasts as big changes are ahead. Read on for more information.                                 

LONG TERM (THURSDAY NIGHT THROUGH TUESDAY): 

     Super typhoon Choi-Wan is completing its merger with a strong trough moving off the coast of Japan and is constructively phasing as was expected. This system will develop now into a powerful mid latitude extra-tropical cyclone with significant ramifications into the Bering Sea and Western Alaska. Following hovmoller's effect of Choi-Wan constructively phasing with the jet stream late Tuesday into Wednesday we should begin to see the effects of the downstream amplification of this system by late Friday into Saturday. Sure enough the GFS, Canadian and EC all show a cut-off upper level low dropping south to around Hawaii while amplifying the ridge across our region before energy from Choi-Wan moves across the Gulf of Alaska and begins to carve out a deep and cold upper level trough across British Columbia by Friday. This system looks to push a cold front into our region later in the day on Friday with gusty winds and a few showers along the surface convergence boundary. Precipitation is not anticipated to be much with initial boundary as it is moving quickly and the vertical motion associated with the convergence is not terribly strong. Cold air will begin to flood into the region from the north by Saturday and will see snow levels begin to rapidly drop from near 7,000 feet on Friday to around 4,000 feet by Saturday. Here is where things begin to get interesting. The models are all now showing the cold trough to drop south into Washington State and form a closed, cut-off upper level low with an abundance of cold air flooding into Montana especially east of the Continental Divide. With all the cold air flooding in east of the Divide a strong surface high also will follow suite which will create a strong north to northeast surface pressure gradient across higher elevations and across the typical areas of favored canyons in North Montana and Lake Koocanusa as well as through the Purcell Trench in North Idaho. Typically northeast winds are not favorable for most of our area to see good precipitation amounts and certainly not for North Idaho as down sloping off both the Divide and the Cabinet Mountains causes drying and stable conditions. This same set up is true across the Tobacco Valley up in northern Lincoln County and across much of the Clark Fork River Valley. This is often, however a good set-up for upslope flow into the east slopes of the Cabinet Mountains and around Libby and McGinnis Meadows. Where the uncertainty lies is often as a cold closed upper level low drops into the region it will develop a surface trough on the east and northeast side of the upper level low and this surface trough is often a focal point of strong vertical motion and convergence producing some good precipitation bands although areas outside of this feature see little in the way of precipitation. This is something we will need to watch carefully as if a surface trough does develop and a deformation band sets up then the mountains could see some impressive snowfall and even some valleys could see some impressive snowfall as well for early in the season. And yes, temperatures will be turning even colder with many valleys likely not rising out of the 40s by Sunday with snow levels down to near 2500 feet. By next week shortwave upper level ridging will build back across the region but there appears to be another shortwave disturbance set to move across the region by Wednesday of next week that could bring another round of valley rain and mountain snowfall. The bottom line is get out and enjoy the fall colors over the next few days as many of them will be gone by the strong winds that will be developing this weekend. In addition, hard freezes will occur across all locations probably by Monday morning as the surface high begins to weaken and slip further south and east following the progress of the upper level low.     

Issued 10/01/2026 8:40 p.m. MDT / 7:40 p.m. PDT

SHORT TERM (THURSDAY NIGHT THROUGH SATURDAY):       

      Fairly quiet conditions remain across the Northern Rockies with flat upper level ridging prevailing across our region with the jet stream directed to our north across Southern British Columbia and Southern Alberta. Passing mid and high level cloudiness will continue to move across our skies but without any lift or vertical motion in the atmosphere to generate precipitation our forecast will remain dry. The mid and high level cloudiness will help prevent valley fog and stratus from developing as well as prevent most valleys from seeing any frost although this is now typical at this time of year. Could still see a few patches of fog and low clouds during the late night and early morning hours in favored valleys, especially across Northwest Montana in Lincoln County but overall fog and stratus will be very limited. Temperatures will rise a couple of degrees each day but have continued to stay below MOS as it appears to be running a bit too warm without any type of wind or mixing. The lower sun angle and rapidly decreasing daylight is working in tandem to prevent temperatures from warming as much as they would in late August or even early to mid September. Still seasonal average high temperatures for our valleys in early October is in the mid 60s and drops into the upper 50s to lower 60s by the middle of next week.                                 

LONG TERM (SATURDAY NIGHT THROUGH THURSDAY): 

     Not much going on in the extended forecast period at least through Thursday. Will be paying attention to typhoon Choi-Wan in the West Pacific as this system is what the models have been having some trouble in resolving its integration into the westerlies by the middle to end of next week. Both the GFS and EC models are showing this system eventually constructively phasing with an upper level trough moving off the coast of Japan but they differ as to where this trough picks up Choi-Wan. This is having some significant differences in the potential outcome in our forecast. The GFS merges Choi-Wan much further off the coast of Japan and closer to Kamchatka as the typhoon becomes extra-tropical. The downstream effect of this produces a weaker digging trough into our region by next weekend with a bit of rain and perhaps some high elevation snowfall. The EC model constructively phases Choi-Wan further to the west and off the coast of Japan into powerful mid latitude system which causes more amplification over the Northwest and consequently brings in a much colder, wetter system by next weekend into our region. This is still beyond the extended forecast period but suffice to say while both models are showing some potential for cooler and unsettled weather by next weekend, they do agree that through next Thursday we will be seeing a dry and stable pattern with broad upper level ridging along with above seasonal average temperatures. Again without much mixing high temperatures will likely not achieve their full potential and have continued to hold temperatures below MOS although it is likely to catch on over the next couple of days. If planning a hike or hunting trip next weekend it will be wise to continue to pay attention to the latest forecast as conditions do look to change by the end of next week. For what it's worth, a MJO signal is evident in the West Pacific which is favorable for further development of Choi-Wan as well as additional typhoon development in this region which has downstream effects on our weather.