Skiers and snowboarders searching for snow have a number of free tools available to them via the internet. The trick is learning enough about each piece of data to know when it can help you find snow and when to ignore it. This article will talk about the visible satellite image and how you can use it to find snow.
Satellite weather data comes from a piece of equipment that sits about 22,500 miles above the earth. Most of these satellites are stationary above a particular point on earth, so they always show the same view of the earth, 24 hours a day, 365 days a year.
Each satellite has numerous sensors that view the earth in slightly different ways. While some sensors are complicated, the visible sensor—what produces the visible satellite image—is the simplest sensor of all. This sensor simply looks down and produces an image from the natural sunlight that falls on the earth. The best way to think about this sensor is that it captures exactly what your eye would see if you were riding on the satellite looking down at the earth.
The visible satellite image helps skiers in two ways. First, it shows the locations of clouds and how thick these clouds are. Areas of cloudiness that appear brighter on the image mean that these clouds are thicker, and thicker, beefier clouds usually produce heavier precipitation compared to thin clouds. Second, it shows areas of snow cover on the ground. When there are no clouds, the satellite can see down to the ground, and if the ground is covered in snow, the ground shows up as white areas that don’t move when you animate the satellite image. While you can’t get specific on-the-ground data about snow from this type of satellite image, it’s still fun and helpful to see where recent storms have produced snowfall.
Unfortunately there are some limitations with visible satellite images. The first drawback is the most obvious—they don’t work at night. When the sun is below the horizon between sunset and sunrise, the visible satellite image shows a dark black screen because there is no light for it to capture. In these cases, it’s best to look at an infrared satellite image, which uses temperature to show areas of clouds.
The second drawback is that a satellite image cannot tell you if it is snowing right now. Because snow falls from beneath the cloud and satellites are looking down on top of the cloud, the best it can do is show that there are clouds and where the thicker clouds are located (remember that thicker clouds often produce heavier precipitation). To find areas where it’s currently snow, you should use radar, though this has limitations as well.
You can now use this quick primer to view visible satellite images with a well-trained eye, but keep in mind that these images are only one tool you should use to look for powder.
Meteorologist Joel Gratz is the creator of opensnow.com and is based in Boulder, Colo.