Bill Burton: It's time for us to take a look at the Science Behind the Forecast as I'm joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.
Tawana Andrew: Good morning. Today's topic is pretty timely, because we could see some of these going on as we head into the weekend.
BB: There's snow in the forecast again this evening, and we're talking today about snow squalls. Tell us about snow squalls.
TA: We usually end up, whenever there's snow squalls, there tends to be a lot of really terrible crashes and a lot of issues on the roads, because they're just not the most fun to deal with at all. The National Weather Service defines a snow squall as an intense, short lived burst of heavy snowfall that can lead to a quick reduction in visibility and is often accompanied by gusty winds.
BB: A clear definition, I like that.
TA: We love to see it. Snow squalls usually occur during the day, but they can happen at any time. There are two types of snow squalls. You have lake effect snow squalls, so when they come off of the Great Lakes, that's usually when we see it. Or with a cold front. Most of the time, snow squalls are associated with cold fronts, and they can move through an area in less than an hour, causing temperatures to plummet, creating white-out conditions that can turn roads icy within minutes.
For things like this to happen, you need a significant temperature drop from the ground up into the mid-levels of the atmosphere around 5,000 feet. This kind of temperature difference creates an unstable atmosphere, which is absolutely perfect for a snow squall to form. You have a cold front that moves into a region like this, and it acts like a convective trigger. Kind of like what we see with springlike thunderstorms. This can lead to snow showers that can pull strong wind gusts. Let's say around 46-plus miles per hour, down from the upper levels of the atmosphere, and you end up with that blowing snow and lower visibility. If you end up with colder temperatures, let's say you have surface temperatures below five degrees Fahrenheit, that can help to enhance the potential for blowing snow and reduce visibility even more. The colder temperatures do make things a little bit worse in many cases.
BB: Colder temperatures generally make everything worse.
TA: That is very true. The fun thing, or I should say, the not-so-fun thing, depending on your view of a snow squall, is the impacts can be very localized. They can happen when there's no ongoing, significant winter storm. You can end up with a situation with one half of a neighborhood getting walloped by a snow squall, and the other half of the neighborhood just seeing sunshine. That is how drastic things can be.
Frontal snow squalls can dissipate under three conditions. One, when the front itself weakens. Two, when they move over uneven or more rough terrain, or three, when they move into a more stable atmosphere. The weakening of that front is actually helping to stabilize the atmosphere, because it reduces the temperature difference between the ground and the mid-levels of the atmosphere. That helps to really just weaken that basically snow thunderstorm. You can think of it that way.
BB: There's a lot to learn about snow squalls, and at least they come and go in a hurry. I guess that's one good thing you could say for them. We have a better understanding of snow squalls now, thanks to this edition of Science Behind the Forecast with WAVE 3 meteorologist Tawana Andrew. Thanks for the knowledge, Tawana.
TA: Of course.
