Colorado is known for big scary avalanches. But some seasons are worse than others. How do we tell if a season is going to be a scary one or a moderate one. A good way to understand it is through the idea of snow climates.
Colorado’s mountains tend to follow the characteristics of a continental snow climate. The continental regime is characterized by a relatively thin snowpack and cold temperatures. This regime leads to a weak, faceted snowpack that’s prone to creating the real killers—the big persistent slab.
For more info on the three climates: Continental Climate, Intermountain Climate, Maritime Climate. See the bottom of the post.
Snow Climates
To understand snow climates/snow regimes, we don’t want to get stuck thinking a specific range is that climate. From season to season, a range tends to produce the characteristics associated with a regime, but that range is not fixed in that regime.
In Colorado, some years we can have a much more “intermountain season” or “maritime storm cycle.” Even though the Colorado rockies are generally accepted as a continental snow climate a Colorado doesn’t always present with that climates characteristics and certain parts of the state has more or less continental characteristics. The characteristics of the individual snow season define the regime—and, more importantly, how we interact with it—not the region it exists in.
Maritime vs Intermountain and Continental. The warm vs the cold
In many ways, we can understand intermountain and continental regimes as shades of the same color, while maritime regimes are a different color altogether. The key difference is temperature.
Intermountain and continental climates are characterized by cold temperatures, with the amount of snow differentiating them. Maritime areas are characterized by notably warmer temperatures.
The big difference between the two colder regimes is the amount of snow—but not just the total at the end of the season. It all comes down to how quickly the snowpack can get to a depth that begins to resist faceting, given the common temperatures associated with that region in the early half of the snow season.
The Continental Snow Climate. The race to 150cm
In broad strokes, faceting will happen in the snowpack given a temperature gradient across it that exceeds 1°C/10 cm. So, if the snowpack is a meter deep:100 cm, a gradient of 10°C is required to cause faceting. This means when the free air above the snowpack is -10°C or 14°F, we will see faceting. Remember, the air under the snowpack stays insulated at around 0°C or 32°F the whole season.
If we reverse engineer that to fit Colorado’s winter weather—where we regularly see temperatures at or below 0°F or -17°C—we need a snowpack at least 170 cm deep before it begins to resist faceting. Anecdotally speaking, it seems when a snowpack gets to be about 150 cm deep, it starts to resist faceting pretty effectively.
The big question at this point is: how bad did the faceting get in the early season. Those layers than now compose the lower portion of the snowpack midwinter snowpack–that rotted out basal layer.
It becomes a race to 150 cm. How quickly can we get a snowpack that resists faceting with temperatures at and below 0°F. Even if it doesn’t get to 150cm right away the more quickly it can get some depth the better. Seasons where we get closer to that 150cm number quickly tend to present more of a intermountain climate and when its high and dry we fit more cleanly into the continental.
Continental Climate
- Location: Typically found in the interiors of continents, away from large bodies of water.
- Temperature: Experiences large temperature fluctuations, with hot summers and cold winters.
- Precipitation: Moderate to low.
- Snowpack: Shallow, weak, faceted, upside down
2. Intermountain Climate
- Location: Found in regions between major mountain ranges, such as the Intermountain West in the U.S.
- Temperature: Moderate compared to continental climates, but still can have extremes due to altitude and topographic effects.
- Precipitation: Moderate to High
- Snowpack: Regularly gains strength early in the snow season
3. Maritime Climate
- Location: Found near large bodies of water, particularly oceans, like in the Pacific Northwest of the U.S.
- Temperature: Mild with smaller temperature ranges; winters are cool, and summers are moderate.
- Precipitation: High
- Snowpack: Deep, humid, strong, rightside up