We use satellite imagery every day to talk about cloud cover, but we can see a lot more than clouds with satellites! A practiced eye will notice certain variations that indicate what looks like cloud cover may in fact be fog, smoke, or snow cover.
A great example of this can be seen on Visible Satellite Images from Wednesday afternoon. You can see what looks like a large swath of cloud cover over the Plains and Midwest region. If you put the imagery on a loop though, you’ll notice that part of that swath of ‘cloud cover’ isn’t moving. That part of the imagery is still because it’s actually thick snow cover on the ground!
It’s well pronounced on Visible Satellite because Visible Satellite works by essential taking photos of the Earth below. That means large features that are colored the same as clouds (some variation of white/gray) will appear similarly to the cloud cover itself.
Infrared Satellite imagery on the other hand measures the temperature of whatever it ‘looks’ at and then colors it accordingly. That makes it easier to tinker with the image’s appearance, by making features below a certain temperature transparent. Here’s an edited view, where the snow cover has been made transparent:
This image is nice, because it more clearly shows where we have cloud cover, but this technique also takes away a lot of detail. Low clouds aren’t as cold as high clouds, which means you could end up taking out some cloud cover while taking out the snow cover. How easily we can make a map appear as (almost) only cloud cover will depend on the types of clouds present and the condition of the snow cover present (any vegetation popping through, melting, and how much sun is reflecting off of the snow can all impact the temperature measured by the satellite).