Nimbstratus clouds can cover hundreds of miles(Sara Beasley / Unsplash)This week on Science Behind the Forecast, learn about nimbostratus clouds and how they create gloomy days. LPM’s Bill Burton talks about clouds with meteorologist Tawana Andrew.This transcript was edited for clarity and lengt h.Tawana Andrew: Today begins our series on clouds. We're getting to the nitty gritty of what's happening above our heads.Bill Burton: There's so many types of clouds to talk about. Where do we start?TA: We're starting with nimbostratus clouds, and these are the ones that are notable for their association with gloomy, dreary, damp days. Kind of like what we've seen recently.BB: Sounds familiar.TA: The clouds in general are classified based on their altitude and their appearance. The term nimbo refers to rain or precipitation in general, while strato or stratus relates to a horizontal layer of clouds. Together you get nimbostratus, and stratus clouds are pretty common in the Ohio Valley, especially during the fall and the winter months when a storm system is moving eastward away from us. These stratus clouds are a dense, thick layer that often produce precipitation.It's the precipitation that makes the nimbostratus clouds a little bit more special. These clouds can typically form in our area between 6,000 feet and 25,000 feet in altitude. If it's raining, then the cloud bases can be a little bit lower, and they overall can extend up to 13,000 feet high in the atmosphere.BB: What do these clouds look like?TA: They are gray and dark, and they have these uneven bases because of the precipitation that's falling out, whether that may be rain or snow, and because of that consistent precipitation that comes along with a nimbostratus cloud. In some cases, the cloud bases may look a little bit more diffused, or may not even be visible at all.The funky thing about nimbostratus clouds is they can stretch for thousands of miles to just a blanket of gray just covering the sky.BB: How far?TA: For thousands of miles I've seen situations where nimbostratus clouds have covered the entire Ohio Valley.BB: That is pretty widespread.TA: From the ground, they look gray and dark overall. But it's important to note that nimbostratus clouds are one of only two types of clouds that consistently produce precipitation. The other kind is cumulonimbus or thunderstorm clouds. Nimbostratus clouds can be incredibly stubborn. They usually don't like to leave an area once they settle in, so they can last for hours or even days. In some cases, some unique cases, when you have some precipitation falling from a nimbostratus, it will fall into a layer of dry air below the cloud. The precipitation may never reach the ground.But if you're flying, let's say you're dry, then you fly into a layer of rain, and then the cloud, and then you fly above it. It's a very wacky thing to experience, but it's cool. While aircraft fly within this deck, they can get very low visibility, often less than 160 feet. Pilots are entirely using just their instruments in those situations, and you can experience some moderate turbulence. But once you get above that deck of nimbostratus clouds, if you're flying, you will see crisp blue skies above it and a layer of gray below you. Honestly, I think it's one of the coolest things that you can possibly experience weatherwise. ...read more read less