ISSUED 01/19/2025 2:55 P.M. MST/1:55 P.M. PST

SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY):

The ever present upper level ridge that has remained either over the Western US or off the coast for what seems like an eternity will remain in place throughout the short-term forecast period. It will retrograde a bit offshore, enough to allow the large and very cold Hudson Bay low to spread further to the west but will not allow any upper level disturbances rotating around this polar low to make it west of the Continental Divide so the forecast remains dry and chilly. Minimal amounts of freezing fog and low clouds will be present the next couple of days with a much drier boundary layer in place now. Will still see some localized areas of freezing fog and low clouds mainly around Priest Lake, Libby, Lake Koocanusa and the other typical fog and stratus valleys during the winter months. Whatever stratus and freezing fog does develop will scatter out fairly quickly. Elsewhere will see hard frosts and freezes which will likely require some significant scraping of windshields if a vehicle is parked outside overnight. Temperatures will drop some on Monday with all locations remaining below freezing and likely remaining there through at least Tuesday and likely beyond. Northeast winds blowing along portions of Lake Koocanusa, through portions of the Clark Fork River Valley, through the Purcell Trench and across higher terrain on Sunday will likely decrease and remain under 10 mph by nightfall which will allow for minimal impacts from wind chills.

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY):

Quiet conditions dominated by the positive phase of the PNA pattern(Western US ridge, Central and Eastern US Hudson Bay low) will remain in place throughout the rest of this forecast period. The only changes of note will be the approach of a shortwave that will help deamplify the overall flow pattern across the North Pacific and North America. While the region will remain in the positive phase of the PNA pattern the Hudson Bay low will begin to flushed out and elongated further east as a stronger subtropical jet merges with the polar jet diving down the backside of it and helping to spin up a strong surface low over the Atlantic. The combined jet on the south side of the Hudson Bay low will be the feature that helps “pull” this feature further east and loose amplitude which in turn helps the Western US ridge loose amplitude aided further by previously mentioned shortwave moving across the North Pacific. This feature looks to begin pushing into the Washington Coast later Thursday into Friday and will bring our region the next best chance of snowfall. This time the event will be all snow as the primary lifting mechanism will be cold air advection instead of our more typical warm air advection ensuring that all precipitation that falls will be snow. Still too early for snowfall amounts at this time but this does not appear to be a large snowmaker for our region but a few inches especially in the typically wetter areas (Bonner County in North Idaho, Priest Lake, Bull Lake, Yaak, Heron) are likely. This system looks to dive south of our region over the weekend with a reinforcing shot of colder air moving south as the Hudson Bay low is showing signs of re-loading once again. Still a lot going on and much can change so will continue to watch. In addition will have to see what the MJO is doing as it appears to be stalled out in Phase Space 1 at this time with only very slow eastward propagation as evidenced by a strong tropical cyclone that has developed off the Northwest Coast of Australia. Stay tuned.

ISSUED 01/12/2025 8:15 P.M. MST/7:15 P.M. PST

SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY):

Quiet weather anticipated for this portion of the forecast. Upper level ridging remains along the West coast with a large and cold Hudson Bay low centered over Manitoba in Central Canada giving North America the positive phase of the PNA (Pacific North America) pattern which is very common this time of year. The upper level steering flow between these two features is northerly across our region with only very weak shortwaves dropping down from British Columbia. The very weak nature of these features is resulting in an overall lack of lift and vertical motion through the atmosphere so mostly clouds with a few flurries or very light snow showers is about all we can anticipate and this will be more favored across Northwest Montana mountain ranges such as the Cabinets, Purcells and White Fish Range. In the lower elevations, varying amounts of stratus and freezing fog will continue in what has been a very dull and drab winter thus far with very little in the way of snowfall and snow cover below around 4000 feet for the most part. This pattern will continue throughout the foreseeable future but some much colder changes are on the way. Read below for more details.

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY):

The pattern for this portion of the forecast will be dominated by a continuation of and likely reinforcement of the positive PNA pattern as the Hudson Bay low reloads itself and gets added reinforcement from additional cold air across Northern Greenland that will rotate its way southwest into Canada and then eventually south into Central and Eastern Canada. Meanwhile the upper level ridge that so far this winter has never really gone away and simply remained anchored across the Intermountain West has recently shifted its axis further west which is where it will remain throughout this forecast period. The ridge will amplify some heading into next weekend as a shortwave zips across the Gulf of Alaska and gets some added jet support with a speed max on the features backside which will help this system intensify a bit and develop a surface low across British Columbia as it traverses the region. This system will bring an increase in winds, initially to the higher terrain on Thursday as it approaches and then as it interacts with a strengthening Hudson Bay low will make a sharp right turn and drop south southeast into Central Montana by Friday. There appears to be enough lift and dynamics with this feature to bring at least scattered snow showers to the region as it passes through especially on Friday. Models may be under-doing this feature especially given this winter season and models tending to over forecast snowfall amounts. These types of patterns in the past have, on some occasions, brought some decent snows to our region. For now will simply introduce chances for snow showers along with locally windy conditions and eventually some much colder temperatures. The biggest impact this feature will have on our region is forcing the Hudson Bay low to become even colder and undergo amplification which will force the ridge to our west to amplify as well. The center of the Hudson Bay low is showing thickness values dropping to near 476 to 480 with corresponding 850 mb temperatures (5000 feet) dropping down to a bone chilling -36 degrees celsius (-33 fahrenheit) across Northeastern Montana. This cold, arctic air will not likely make it over the Continental Divide but our region will experience cold polar air rotating into the region with the upper level flow coming straight down from the north and near Baffin Island in far Northern Canada. 850mb temperatures across our region look to drop to between -6 to -12 degrees celsius (10 to 20 degrees fahrenheit). This will likely result in the regions first sub-zero temperatures of this relatively mild winter season thus far but unfortunately, with the lack of snow on the ground across most valleys, this will also likely lead to the ground freezing and an increased potential of bursting pipes so keep this in mind. Overall confidence in a much colder weekend is rather high as is an overall relatively dry pattern remaining unfortunately. The good news is that it appears that the MJO (Madden Julian Oscillation) is beginning to amplify in Phase Space 2 which corresponds to the upcoming pattern. It will likely then progress into Phase Spaces 3 and 4 which corresponds to a much wetter (and hopefully snowier) pattern as we head into the end of January and into February. Stay tuned!

ISSUED 01/07/2025 7:00 P.M. MST/6:00 P.M. PST

SHORT TERM (TUESDAY NIGHT THROUGH THURSDAY):

Rather dull and dreary day across the region with clouds covering the entire region except for the very highest peaks above 7000 feet which were above the stratus and stratocumulus deck that is entrenched across the region. Not likely to see much if any sunshine at least in the valleys over the next several days and possibly longer as our overall pattern favors strong inversions remaining locked in place as no strong storm systems or strong surface highs east of the Continental Divide are showing up to produce much in the way of mixing. A very weak shortwave will push through the region overnight and may produce just enough lift through the cloud deck to squeeze out a couple of snow showers but any accumulations will be extremely localized at best and generally confined to locations above 4000 feet where, in the best case scenarios might see up to an inch of snow and even that is really stretching things. The shortwave will exit east of Northwest Montana by early Tuesday afternoon with upper level ridging amplifying behind the departing shortwave. The ridge never really leaves the area but the shortwave will help flatten the ridge somewhat as it passes by which is why we may see a few flurries or light snow showers from the shortwave. As the ridge amplifies back across the region will see a lowering of the cloud deck back down to the valleys with elevations above 4000 feet in North Idaho and above 4500 to 5000 feet in Northwest Montana likely to see a fair amount of sunshine by Thursday. This will be wonderful news for those of you headed up to the local ski areas as Schweitzer and Big Mountain should see plenty of bluebird conditions on Thursday. Turner Mountain is closed Thursday but the summit will likely see some sun as well as it should be just above the stratus deck.

LONG TERM (THURSDAY NIGHT THROUGH TUESDAY):

Ridging will deamplify once again on Friday as a slightly stronger and more robust shortwave trough dives in from the northwest. This feature is showing better upper level jet support, vertical motion and surface convergence to help generate a bit more snow out of it but amounts do not look anything to be excited about. Preliminary estimates are for at the very most 1 to 2 inches in the valleys and 2 to 4 inches in the mountains above 4000 feet but the way this winter has gone thus far, I wouldn’t count on it. Thereafter some realignment of the overall placement of the upper level ridge will take place with a bit of retrogression of the axis to offshore which will place our region in a colder, northerly upper level steering flow but it looks like we will remain on the anticyclonic side of the jet stream which simply means that our region is more likely to be influenced by the ridge and its sinking motion rather than the cold upper level trough on the cyclonic side of the jet which generates vertical motion and precipitation. Still a couple of weak shortwaves look to drop south from Canada in close enough proximity to our region to support a slight chance of snow showers at times. What is more likely is that valley locations will continue to be plagued by the never ending sea of stratus and freezing fog. With the mild and largely snowless winter in the lower elevations below 4000 feet, a saturated ground that is not frozen, despite not having any snowcover inversions persist and the saturated boundary layer and lack of low level mixing will keep low clouds in the valley locations until a couple of things happen. 1. The pattern changes to an active one with colder temperatures, more snowfall and more wind to mix out the stratus. 2. A polar or arctic airmass descends out of Canada bringing bitter cold temperatures and winds. 3. The sun angle gets high enough in the sky to help warm the surface and cause the stratus to mix out. This last scenario however is not likely to occur before the middle to end of February which is when the sun angle is high enough in the sky to begin to cause the stratus to break up in the afternoon. Looking way out into Fantasy Land there are signs that we may finally begin to see a more winter-like pattern beyond 10 days. Not going to elaborate too much yet but it is something that is starting to become more consistent in the long range models so confidence is very very slowly increasing that a break in this “lack of winter” pattern may settle in. Stay tuned.