The Coast Mountains are an amazing mountain range. A large part of that is due to it's proximity to the ocean. Mountains, as is their nature, cast a rain shadow. What this creates is a variety of climates in the Coast Mountains as westerly winds hit the mountains and undergo orographic lift, dropping various amounts of precipitation. In this post I talk about the different mountain climates between Bella Coola and the US/Canada border. I describe the different climate's characteristics and how it pertains to the areas overall weather, glaciation, snowpack and vegetation. First of all, I am not a scientist and this information is a generalization that comes from experience in the different climates, and through recognizing a pattern throughout the SW Coast Mountains. As you can imagine you may experience a variety of different climates in different areas due to local weather effect and topography. The nomenclature I'm using is also improper. Let's begin with furthermost left.
The Western Edge: Temperate Rainforest
Marked in Green on the google earth overview map, this amazing zone is special. It's a rare climate known as Temperate Rain forests. At lower elevations you'll see large Devils Club, Sitka Spruce, Hemlock, Red Cedar and lots of moss. This climate is wet and lush. As weather systems from the pacific are blown from the west, these are the first mountains they hit. The result is lots of precipitation. Examples include the mountains surrounding Bella Coola's town site, the North Shore Mountains, Squamish's Tantalus Range, etc. The mountains here in general are rarely higher than 2500m but average 1500-2000m instead. They rise abruptly over the ocean. Fjords cut into these mountains acting as moisture highways.
This snowpack is the characteristic "Coastal Snowpack" everyone thinks of when they think of the coast mountains. The snowpack is simply enormous ranging from 2-5 meters deep. The snow often falls wet, nicknamed "Coastal Concrete" by the sadistically fond. When it falls, watch out! Deep storm slabs will form and rage down the mountain side but once the skies clear it doesn't take much more than 24hrs before things settle and you're left with that bomber snowpack. If you're familiar with this climate you'll have noticed the oxymoron "when the skies clear". It's more of an 'if'. Snow can fall so continuously throughout the winter months that these climates require shelters, huts or going home at the end of the day. This also restricts most exploration to the spring and summer months.
The glaciers form at lower elevations compared to the rest of the range sustained simply by the precipitation despite the mild temperatures. The mountains are rugged and the glaciers often roll off hanging valleys or drop over precipices. Expect most glaciers to be rugged and challenging.
The Icefields: Massive Glaciers and Mountains
Marked in light Blue on the google earth overview this is the most expansive environment in the Coast Mountains. Here the mountains are larger, taller and metamorphic events have created high icefield plateaus which catch huge amounts of precipitation. Mountains range from 2000-3000 meters high on average with the exception of the Waddington Range which climbs from 3000-4000m. In this climate you'll find much of the same ecology as in The Western Edge but with large rivers and lots of glaciation, most vegetation is non existent except at lower elevation. Heather dominates at the alpine/treeline elevations. Although lots of precipitation has been dropped on the Western Edge, the Icefields continue to catch a ton of snow and rain due to their size. They cause even more lift and will receve a similar if not more precipitation. These areas often create their own weather. Sometimes cold air on the icefields will create miniature arctic highs which can keep weather at bay as clouds float around the cold dense air. At other times the high mountains will hold the weather and have their own clouds when everything else is dry. Mount Waddington is a good example, dubbed the "Misty Mountain" in its earlier days for the weather it generates. Other examples include Garibaldi Park, the Lillooet Icefields, the Pemberton Icecap, etc.
Very similar to the snowpack described earlier for The Western Edge. The difference being that at higher elevation in The Icefields the snow doesn't fall as wet. It may take a little longer for storm slabs to settle but the overall large amounts of precipitation make for a stable snowpack. Persistent Weak Layers (PWL's) may start to exist more at times due to surface hoar from low elevation fog bands or high elevation cold clear spells. Again, most high alpine self propelled travel is reserved for the spring and summer. This zone in the coast mountains is what snowmobilers relish in and what makes the best long distance ski traverses.
Glaciation: The glaciers as you can imagine are enormous and widespread. This is the most glaciated climate in proximity to the equator anywhere in the world. That is to say the largest glaciers that you will find so close to the equator. The glaciation rivals Alaska, the Yukon, etc. The higher elevations and colder temperatures combined with huge snowfall amounts and continuous cloud cover make for large flat icefields and rugged glaciation which drains into large river valleys.
Skipping over a zone, it's best to talk about the Chilcotin Climate before going on to the Transitional Climate. The Chilcotins are becoming reputable for their mountain biking now and the zone is marked in Yellow. By the time the clouds have reached the Chilcotins they are riding high and only have a little bit of moisture left to drop. These are essentially the Rocky Mountains of the Coast Mountains and are incredibly special and stunning. The ecology for the most part is quite different with much more alpine meadows and high tundra. Forest fires here are more common and take part in the ecology as more fire resistant vegetation takes root. Pine trees, interior douglas fir and ponderosa pines intermingle with the spruce and mountain hemlock. The mountains are high as they sit on the edge of the Chilcotin Plateau and range from 2000m-2800m. Trees also easily grow to 2200m depending on aspect. Examples of this zone include most of the Stein Valley, Taseko Lake, the Eastern Duffey and Eastern Pantheons. Often pouring rain in Squamish will be a mere drizzle in Lillooet if nothing more than just overhead clouds.
This is a more interior snowpack. Shallower snowpack induces more faceting and more cold dry spells also encourage surface hoar growth. These layers aren't as likely to get squashed out by more snow. At the same time the snow is drier and quality predominates quantity. On average a 1 to 2 meter snowpack is more common. The light dry snow is vulnerable to wind transport so you can expect windward areas to be as shallow as 20-80cm while some pockets might accumulate upwards of 2m. Unlike the Rocky Mountains, the Chilcotin zone won't get as many arctic highs and precipitation often remains continuous in smaller quantities than out west.
Glaciation: At times almost inexistent. Small pocket glaciers on shaded aspects on the higher peaks exist but they are few.
The Transitional Zone:
The Transitional Zone, marked in Red is essentially that magic divide between the Chilcotin and the Icefields Zones. The weather is a mix between coastal and interior and at different intervals gets the best (and worse) of both worlds. What this means is an amazingly varied climate which ranges from dry to wet depending on specific topography or the particular weather system. The ecology is a split as well and you'll see a mix of douglas fir, pine, cedar, etc. The Duffey Lake Road is well known as a great skiing destination near Pemberton and it exhibits that amazing climate well. Other examples include Lizzie Lake near Lillooet Lake, Chilko Lake and Stuie in the Bella Coola Valley. Mountain elevations range from 1800m-2400m on average.
The Duffey Lake road is reputable because it gets both good quantity and great quality of snow. It's a big broad mix of weather which at times will resemble the Chilcotins while at other times the Wet Coast. It varies from 1-3 meters deep.
As you might expect the glaciation is a mixed bag. There is less than in the Icefields Zone but more than the Chilcotins.
Overall I hope you enjoyed this post and have a better understanding of the different climate zones in the Pacific Ranges (SW Coast Mountains.)
Ps: Forgive the mis-spelling of Lillooet on the Map