Centred Outdoors: What can clouds tell us about weather?
One thing you are always guaranteed to run into when exploring our region is the weather. While we have come a long way from simply looking at the sky to try to predict the weather, there is still a lot you can tell from a quick glance up at the clouds.
Clouds are a key indicator of incoming weather conditions. They can be roughly categorized into four main names based on their formation and function — cirrus, cumulus, stratus and nimbus. While there are far more than these four simple groups, properly identifying a cloud type usually involves a combination of two or more of these names to describe the shape and purpose.
Cirrus clouds are high-altitude clouds that are mostly made of ice crystals. These can appear as hazy clouds in feathery wisps or be seen blanketing the entire sky. These clouds will often arrive a day or two before a prolonged rain system. At night they can create halos around the moon and small rainbow refractions during the day.
The classic, big puffy summer clouds are cumulus clouds. They are generally formed through convective air masses rising and condensing. When they are in their puffy stages these clouds pose little risk, but as convection rates increase, usually due to more and more input from uneven heating of the Earth by the sun, they can transform into a towering thunderstorm flying by on a summer afternoon.
Stratus clouds form the dense, darker blankets that fill the sky for days-to-weeks in the winter. Thankfully less common in the summer due to our region’s climate, these clouds bring fog, light rain and sometimes a flurry of snow.
The major rain-bearing clouds are in the nimbus family. These clouds are almost always dark gray or even black due to the shear amount of water they contain. The nimbus name is never really used on its own, but instead modifies one of the other cloud types to note its likelihood for producing precipitation.
The shape and type of land can contribute to cloud formation and weather. While this region lacks truly massive mountains that drive entire climates like the Cascades in the northwest or the Andes in South America, our ridges trap low-level moisture and often create updrafts that stretch thousands of feet into the air. This region also experiences an effect known as a temperature inversion where a layer of warm air sits on top of cold air trapped in the valley. This is mostly visible in the winter and can be seen when a low-level layer of clouds or pollution sits it the air with a hard line at its upper limit.
There are many nearby places that have expansive views or regularly exhibit an unusual weather phenomenon. A strong western view or otherwise unobstructed view of large swaths of the horizon are hallmarks of great places to watch our changing weather. Of course, potentially dangerous weather such as thunderstorms are best viewed from inside a vehicle or building.
The Barrens to Bald Eagle Wildlife Corridor is exactly one such place to find a great view. Positioned on the mid-valley ridge it is elevated a few hundred feet above most of the valley. If there is a cloud to be seen, it will be visible from the trails in the corridor. This area also exhibits a unique phenomenon due to the presence of the very sandy soils — the surface temperature often falls well below the surrounding regions. This “bubble” of cold can often cause storms to generate intense rainfall over the barrens or for clouds to form as they are forced to rise over the dense air mass close to the surface.
Rhoneymeade Arboretum and Sculpture Garden offers a similar type of view as the corridor through the Nittany ridgeline obscures the true western horizon. It does not stop the wind, however. Intense wind is almost constantly blowing from the west as the ridgeline acts as a giant funnel focusing any ground-level flow to the northeast.
Mount Nittany, while able to generate weather all by itself, offers spectacular vistas facing into oncoming weather. From the westward face you can often see weather just as it begins to peek over the top of the Allegheny Plateau.
Black Moshannon State Park also lies on the Allegheny Plateau, but further north from the Allegheny Front. This front is a significant elevation increase at the edge of the plateau, causing cold air to be trapped on the windward side throughout the year. This has an interesting effect on the weather around us, often causing storms to stall along the front, increasing the likelihood of snow or other freezing precipitation.