Winter 2019/2020 Outlook for Northwest Montana

Here it is the end of November and the most common question I have been receiving over the past month or so has been “What kind of a winter will we have?” My apologies that I have taken so long to get this winter outlook written. This year is proving to be more complicated than in years past as overall there is no clear signal one way or another to determine with high confidence how this winter will play out. A lot of important factors such as ENSO (El Nino Southern Oscillation), the PNA (Pacific North American) set up, the MJO (Madden Julian Oscillation) are all showing rather weak signals thus far with no clear trend in one direction or the other. In addition, snow cover has been quite variable thus far this fall which often signals where the Hudson Bay low will set up along with unusually warm waters not just in the Northeast Pacific but also across Hudson Bay in Canada which is showing limited ice growth thus far although during the past few weeks ice cover has expanded a bit more rapidly across western Hudson Bay but largely the region is ice free. All of these factors have combined produce a highly uncertain winter outlook. At this time here is what the Climate Prediction Center is showing for the upcoming winter.

The above graphic shows the 3 month temperature outlook for the US with our region falling in the 33% range for odds favoring above average temperatures for the months of December, January and February as of November 21, 2019. The next graphic shows the 3 month precipitation outlook for the same time period for the US.

For our region the Climate Prediction Center is showing our region falling in the 33% range of odds favoring above average precipitation . So in summary, if we were going by what is being shown here our region could expect better chances for a milder winter temperature wise and potentially a wetter (or whiter) winter concerning precipitation. This outlook does not mean that the Climate Prediction Center is saying we will have a warm or mild and wet winter but the overall odds favor the winter being milder and wetter than average. We still could have cold air outbreaks as well as significant snows. While I don’t really see any fault in this prediction given how much uncertainty there is, narrowing things down a bit and focusing more on Lincoln and Sanders Counties here is what I have found for our region. Take a look at this next picture which shows snow cover across North America as of November 29, 2019.

As you can see from this picture much of Canada is currently covered in snow with the central part of British Columbia largely snow free. Much of the Western US is snow covered simply the result of the Thanksgiving storm that was unseasonably cold and produced large amounts of snow over much of the Western US. The other area of note is the lack of ice over Hudson Bay and the Labrador Sea between Canada and Greenland. This lack of ice, specifically across Hudson Bay is very important for our region as Hudson Bay’s ice or lack thereof will often foretell where the Hudson Bay low will set up it’s winter residence. The Hudson Bay low is simply a large and cold upper level low that is generally a permanent feature across much of Canada but is more pronounced during the winter months and is often the driver of the very cold polar and sometimes arctic air mass outbreaks that sweep down into the Midwest and Eastern US and sometimes even into our part of Northwest Montana. The corresponding feature along the Western US is the East Pacific upper level ridge which is simply a large and “warm area of high pressure aloft that simply acts to block Pacific weather systems into our region but also helps feed cold air from Alaska and the Yukon in Canada into the Hudson Bay low. The two features work together across North America and where they set up as well as their amplification or lack thereof are very important to weather across North America. Unfortunately I do not have a map of one other very important feature that may help determine our winter and that is the “blob” of unusually warm water that is currently located some 1,500 miles west of the British Columbia coastline. This is important for our weather as the East Pacific upper level ridge will more than likely establish nearer this relatively warm body of water.

Based on the information I have described above here is my 2019/2020 Winter Outlook for Lincoln and Sanders Counties. I believe in a nutshell that our region will see below average temperatures (colder than normal) with near to above normal precipitation (mix of rain and snow on valley floors with slightly better odds for more snow than rain in the valleys). This prediction is based on the Eastern Pacific upper level ridge setting up well offshore thus keeping our region in a general Northwest upper level flow which would allow colder weather systems to drop down from the northwest. If the Eastern Pacific upper level ridge does indeed set up well offshore then the corresponding Hudson Bay low will also likely set up farther west, perhaps over Manitoba or even Saskatchewan and not over Hudson Bay. This seems a bit more likely at this time with Hudson Bay not frozen over yet and the relatively “warm” waters serving to deter the establishment of the Hudson Bay low over that part of Canada. With the rather persistent snow cover across Manitoba and Saskatchewan this has a bit of the “refrigerator effect” thus causing the Hudson Bay low to become established more over this region. This of course then places Northwest Montana in a sort of battleground region between the warmer bias of the East Pacific ridge and the colder bias of the Hudson Bay low. The Climate Prediction Center is basing their forecast more on the East Pacific Ridge being closer to the West Coast giving us the milder temperatures but with the jet stream in close enough proximity to give us more storminess. As I have said before this outlook has proven to be rather difficult this year as there are really no other years that I have been able to analog and compare things with to get any ideas as to how this winter looks for us. One other note, however that leads me to believe we will end up a bit colder than average is simply a more recent development along the West Coast. With the warm water “blob” having shifted further west in the past couple of months, colder than average water temperatures have begun to surface along the southern British Columbia, Washington, Oregon and California coastlines and have actually begun to expand farther offshore. This also favors more upper level troughing over the Western US verses warmer waters which favor upper level ridging. Finally for those of you who are new to our region or simply don’t really know what an “average” year brings temperature and precipitation wise to our region here is some data. Typically valley locations in Lincoln and Sanders Counties for December, January and February see high temperatures in the lower to mid 30s depending on your locations with colder highs typically found in Libby and Eureka and warmer highs found around Thompson Falls, Trout Creek and Heron. Valley snowfalls average between 55 and 85 inches with the lower end of that typically found around Eureka and the higher end of that range around Heron and Trout Creek, two of the snowiest towns in all of Montana (Libby’s average annual snowfall is 65 inches). Of course the mountains typically see much more snowfall, closer to the 250 to 300 inch mark in the Cabinets around 6000 to 7000 feet but no one lives up there. So there you have it, in summary I think prepare for a decent winter that is likely to have it’s fair share of cold air outbreaks as we have already seen several times this fall. This winter outlook also carries a very high bust potential but have given this much research and my best guess. Hopefully we won’t have any record setting cold this winter but I would love to see some record setting snowfalls, just saying…. Bottom line is, this is Montana so be prepared for anything! Please feel free to share your thoughts and comments!