One thing you are almost 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 the harbingers of all manner of 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 or even small rainbow refractions during the day.
The classic puffy summer clouds are cumulus and are generally formed through convective air masses rising and condensing. When they are in their puffy stages these clouds pose little risk other than a sore neck from staring up at their beauty. As the convection rates increase, though, usually due to more and more input from uneven heating of the earth by the sun, cumulus clouds can transform into a towering thunderstorm flying by on a summer afternoon.
The bleak stratus clouds form the dense blanket that fills 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 the sometimes a flurry of snow.
Nimbostratus clouds producing rain
The major rain-bearing clouds are in the nimbus family. These clouds are almost always dark grey 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 denoting its likelihood for producing precipitation.
The shape and type of land can contribute to weather formation. 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 can often create updrafts that stretch thousands of feet into the air. We can also experience 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.
Scale reference for weather systems
Category 4 Hurricane over the Gulf of Mexico and Mid-latitude cyclone from Bermuda to Greenland
Source: NOAA August 26, 2020 7:00 PM EDT
Once these formation forces begin, they are swept along by the balancing of large-scale differences in pressure across the planet, also known as wind. This is how weather systems form and is the main driver in weather changes from day to day. These weather systems often take the form of a front, or a place where there is a significant change in the quality of the air on either side of an imaginary line. Most commonly this is a difference in temperature, hence the “warm” and “cold” names often affixed to them. The temperature difference causes all kinds of interactions that require intense computer modeling to even begin to predict their motions. There is one type of motion that is well documented and is the classic source of our weather patterns, the mid-latitude cyclone.
Mid-latitude cyclones are much larger than hurricanes and form through a much different process than their more famous sub-tropical cousins. These continent-sized systems are characterized by a circulating flow of air that brings a combination of long rainy days followed by thunderstorms, heavy winds, or intense snowfall and cold temperatures. They are usually referred to by other names such as bomb cyclones, Nor'easters, Alberta Clippers, or other regional “lows.”
Observing the weather can be done in most places simply by looking up. However, there are many 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 seen 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 airmass 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.
Mt. 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 also lies on the Allegheny Plateau, but further north from the Allegheny Front. This front has nothing to do with the weather types previously mentioned, but rather is a significant elevation increase at the edge of the plateau. This lip causes cold air to be trapped on the windward side throughout the year. This has an interesting effect on the weather, often causing storms to stall along the front, increasing the likelihood of snow or other freezing precipitation.