Weather Terms You Should Know...

October 8, 2021 // Article by: Bobby Bianco

In the weather world, we have plenty of terms that we use in our forecasts such as Alberta Clipper and Virga but what exactly do they mean? Thankfully, Mike Mihalik, Brad Miller and Mike Priante helped us out on an episode of "The Weather Lounge". 

First we'll start with virga. This is a weather phenomenon which occurs mainly in winter (but can occur year-round). This is when snow or rain begins to move into a region, but the airmass that it's moving into is so dry that the precipitation falls from the cloud and evaporates or sublimates before it reaches the ground. During a snowstorm, typically the storm moves into a dry, arctic airmass and as the snow falls from the clouds, it is saturating the air. It saturates the air by evaporating which releases moisture. Once the flakes begin to make it to the ground, the air from the cloud to the surface is saturated and precipitation can fall freely. 

A term that goes along with virga (like milk and cookies) is an Alberta Clipper. These quick moving snow producers are from Alberta, Canada (where the name comes from) and are accompanied with a lot of dry, arctic air. Most of the time, if there is a clipper moving in, you can probably look at the radar on whatever app you use and it will look like it's snowing at the onset, but it may not start for a few hours...this is virga. To be clear, a radar shoots out a beam of radiation on an angle. The farther away the beam is from the radar, the higher the beam is, so while it might be picking up snow at 5000 feet, if the beam was lower, it would not show it snowing since it is evaporating on its way down. Nonetheless, since Alberta Clippers come with arctic air, they can produce high ratio snow. On average, the "typical" rain to snow ratio is 10:1.  In other words, for every 1" of liquid precipitation that falls, it would equate to 10" of snow.  Snow associated with an Alberta clipper is usually "high ratio" snow.  So, if there is 0.10" of liquid that falls from one of these clippers it could easily add up to 2 or 3 inches of snow. This is a very light and fluffy snow that can be blown off a car, or the ground very easily. 

Moving into the warmer season, do you know what a microburst is? Here's how it begins. A thunderstorm with a strong updraft forms and holds precipitation in the cloud. When the updraft weakens and can no longer hold the precipitation, it is released and all of the precipitation falls to the ground very quickly with strong winds. Microbursts produce straight-line winds, and while it may look like a tornado went through, but damage surveys can determine the actual source. If there is a lot of damage in a straight line (Downed trees facing the same direction) then it was straight-line winds and likely a microburst. However, if there is damage in multiple directions (typically cyclonic or counter clockwise), then it was most likely a tornado. 

This is a gif of how a microburst looks as the air from high aloft in a storm crashes to the surface. Courtesy NWS Birmingham.

There are plenty of other terms that were defined in this podcast with so much to learn! Definitely a good listen, so head to the website and check it out! .

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