Researching snow levels

Background

As I’m planning to start my hike earlier than usual, I need to do some in-depth research on what kind of weather conditions, especially snow depth, I would encounter. Prime hiking season in the Canadian Rockies is from around early July to mid September, and hardly anyone starts the GDT before late June. When I first asked questions about starting in early June on the Facebook page (which is actually super helpful!), everyone told me my plan is not going to work out. The reason given was always “too much snow”. But what does that mean? What is “too much snow”? Will I need to bring crampons, micro-spikes, ice axes, skis or snowshoes? Or is it impossible to do the trail even with this gear? While I always appreciate input from experienced locals and hikers familiar with the terrain, in this point in my hiking “career” I like to ultimately make my own decision based on assessing the conditions myself. But how do you assess conditions for a region you have never been to?

Available resources

The first order of business is to identify publicly available resources that have historical snow level data available. As always, Andrew Skurka has some great posts describing his process for a variety of different data points (weather, precip, snow) on his website:

• Be Prepared? Absolutely. But against what? Why and how to assess environmental and route conditions.
• Tutorial: How to predict backcountry weather conditions
• Sample: Environmental and Route Condition Assessment

Andrew also covers this extensively either in the planning curriculum if you do a guided trip or in his online planning course. In 2021, I did a trip in the Brooks Range in Alaska with his company, which gave me some great experience prepping for these kinds of trips. As Andrew does most of his trips in the US, some of the resources he mentions in his articles are not available for Canada. For example, I typically rely on SNOTEL to get snow levels in the Sierra Nevada, but I realized that the Canadian stations are not all listed there. Instead, I found a great map for BC and an okay map for AB that much more specific to the Great Divide Trail. The AB map was kinda hard to use, so I was glad I found the same station information provided by the Northwest River Forecast Center.

Once I identified the webpages for the snow sensors, I had to find relevant ones for the Great Divide Trail. Some sensors are either too far away from the trail, or in valleys that might not be applicable at all to the GDT. This is where Caltopo is super useful, as you can add weather stations as a layer and then easily identify stations close to your route. However, there are two drawbacks with this method: a) Again, the sensors I found were quite far from trail and b) Caltopo shows only current conditions, which is not great for long-term planning. I’m not interested in the snow level in November or December (when I did most of my research), but in historical normals for June.

So back to the maps by BC and AB, respectively. With some sleuthing and map comparisons, I found a couple of stations that were much closer to the trail, sometimes even on the trail. Once I’ve identified them, I extracted their location and added them as markers to Caltopo. I added sensors all the way up to the end of the trail, however, I didn’t anticipate those to be particularly relevant because by the time I hit that section, it should be late enough in the season for snow levels to no longer be relevant. However, this was a classic “better safe than sorry” situation.

Getting the data

Once you identified the relevant stations, the next step is to get the actual data for those sensors. Ideally, what I’m looking for is a chart or table with the normals for the last two decades (typically what’s available) and the values for the current year as bonus. Assuming that your stations are available, the NWCC report generator is amazing. As mentioned earlier, not all relevant stations however are available on there. I started with three different sensors that I could easily identify on the report site:

• Flattop Mountain, in Glacier NP south of the Southern Terminus of the GDT
• Morrissey Ridge, in a valley next to the GDT in Section A
• Flow Lake, right on the trail in Section C.

Using these settings for the report will create a nice chart (see below), showing you both the historical values and current year values. The online version is interactive and easier to read than the static image. Now if all your stations are available, you’re done! Create reports however you want them, and bam. In this case, it was a little trickier.

While I managed to find some more stations from BC and AB on the report website, it was missing some values, such as only having one data point per months for the normals, and no current values. Without those values, I didn’t find the data that helpful, especially as I was curious how fast the snow melts in June. Unfortunately, I didn’t find a super convenient way to create similar graphs across multiple stations, but resorted back to creating them individually. On the Rivers Alberta page, you can click the station and select “Yearly Graph”, which results in a nice graph showing exactly what I need. As mentioned earlier, you can get the same graph presented slightly differently by the Northwest River Forecast Center. For the BC stations, you can similarly create nice reports and graphs on their website, for example for Wildcat Creek, or by bookmarking the direct link.

Analyzing the data

Now we got all the necessary stations identified and know how to access the data, you actually need to interpret them correctly. You might have noticed already that the y-axis doesn’t describe snow depth itself, but something called Snow Water Equivalent (SWE), which essentially describes the volume of water the snow would correspond to once melting. It thus ignores other factors like the density of the snow, which will ultimately tell you how deep the snow is. The same SWE can result in a tightly packed low snow level with a nice ice crust on top, or a high level of super powdery snow. I find that the most informative measure is not necessarily the absolute value of SWE, but the relative one compared to what is normal, and/or to other places that you are familiar to (e.g. I could compare it to similar levels in Yosemite or other places in the High Sierra, a place I’m much more familar with than the Rockies).

Historical levels

The first step in analyzing the data is simply looking at the historical normals, ideally both the median and the lower and upper quartile. The median will divide the values into neat halves, where 50% of values are above the median, and 50% below. The range between the lower and upper quartile will describe the “middle” 50% of all values, which I basically interpret as the “normal range”. If the values go above the upper quartile (75%), you know it’s a heavy snow year. Unfortunately, the AB graphs don’t show the median but last year’s values instead.

If you click through the graphs (fun, isn’t it), a clear picture emerges: At the start of June, you can expect about 400-600mm (15" - 23") of SWE across the board, but at the end of June, most if not all the snow will have disappeared. This is quite a rapid snow melt, which will also mean creek crossings might potentially be dangerous towards the end of June and start of July. By looking at the lower quartile of the data, you can also tell easily that there is a really, really low chance there won’t be any snow on the trail in early June. By starting on June 1, you are more or less guaranteed to encounter snow, but if you start in mid June, the snow will have already considerably melted in a normal year.

For my planned itinerary, this basically means that I will encounter snow until the end of Section C, and possibly start of Section D, but that is is very unlikely I’ll hit major snow after that, which matches with my earlier intuition.

Current year levels

Now that we have a baseline identified of what to expect in a “normal” year, it’s important to remember that hardly any year is “normal”. There are always deviations, and it’s of little comfort to know what another year looked like in comparison to the year you’re actually in. And again, a pretty clear picture emerges by looking at the current year’s values: It’s a heavy snow year (yay, lucky me!). But, if you look a little closer, most graphs show a very interesting pattern: A sharp and sudden increase in early/mid November. And in fact, there was a major storm during that time that hit the Rockies. The rate of change since then has mostly paralleled the normals, indicating that most of the snow has dropped during that storm and stayed since.

Predicting the future

Ultimately, the snow levels in early February are also irrelevant, unless you are hiking in February. They can, however, give you some indication of what the levels will be like in June. It’s not quite time to panic yet. A warm spring can melt the snow pack much earlier and quicker than normally, but on the other side, it is also possible another snow storm will dump even more snow. Compare this to what is happening in the Sierra Nevada right now: A record December followed by an incredibly dry January, averaging out to around a normal snow pack (for now),

Supplementing the data

Numbers are numbers, but I like to supplement them with other ways of gathering information. I was lucky that there are some really well documented June trips:

• Dan and T Durston’s June yo-yo, documented in Dan’s blog and T’s blog, as well as a great video series.
• Magpie and Constantine’s June start is also documented in blog and video form.
• The earlier mentioned Facebook page also has some pictures and descriptions from other June starters.

And as I alluded to in the introduction, getting first person accounts and opinions from experienced hikers can be incredibly useful. I was lucky that Dan is a very helpful guy, and has answered a ton of my questions. He is on the GDTA board and knows the trail like probably no other. Another great resource has been Andrew Cotterell, a Canmore local, who set the FKT last year (thanks to Stringbean for putting me in touch). And while not having personal experience on the GDT, Andrew Skurka was helpful in weighing my personal skill level to the expected conditions.

Conclusion

I hope this was a helpful walk-through on how to assess snow levels and conditions, not just for the Great Divide Trail but in general. Ultimately, nobody can make the decision for you, and you have to weigh your experience and comfort level to what you see. From the research I have done, it’s pretty obvious to me that by starting in mid June instead of early June I would have a much easier experience. However, in this case, I’m intentionally seeking out the challenge, and as I’m planning to yo-yo, I’m looking forward to seeing the same sections both in early spring and the middle of summer. For the majority of thru-hikers, a late June to early July start makes a lot more sense if you’re looking for a “typical” three season experience.

The other take-away from this research is my gear selection. I will be 100% bringing snow shoes and if the current situation pertains, an ice axe. Micro-spikes should be not necessary with the snow shoes, as I’m bringing full sized ones compared to the Durstons, who brought more minimal kid’s shoes. As the data shows, I should be able to drop of the snow shoes after Section C, and switch to regular three season gear. Other adjustments I’m making are to bring thicker socks, dedicated sleeping socks, bread bags for camp shoes, and potentially my Apex booties and mittens. I’d be happy to do a deeper dive into my gear selection if there is interest (spoiler: I won’t hit a 10 lbs base weight).