5:29 PM EST, January 27, 2013
Extremely cold temperatures settled in over the Tri-State region last week, and with it came a couple small snowstorms that deposited several inches of accumulation.
But did you notice how the snow was very fluffy and “drier” compared to snowfalls earlier this winter?
Snow shovels were not needed in most cases for clearing off cars and driveways — a simple household broom or even a small leaf blower seemed to do the trick quite easily for most people around Hagerstown.
And it’s especially not good snow for snowball fights or making snowmen, according to HMTV 6 Meteorologist Brittany Beggs, who on Friday explained what was taking place high in the atmosphere to create the lightweight snowfalls last week.
“This stuff ... if you walk in it, this is going to be a little more light and a little more fluffy,” she said. “If it’s warmer, it’s going to be that wet stuff. And it makes it more slick when you’re traveling.”
Beggs said the fluffy snow is caused by frigid temperatures, which are due to an arctic air mass, called a “trough,” that settles over a region thanks to a shift in the jet stream high in the atmosphere.
“Usually it’s up in Canada, and that trough allows that cold air to come southern, so that’s when it reaches the United States,” she said.
With such cold temperatures, Beggs said very little moisture is needed for sizable snow accumulations, like the several inches that Washington County and the surrounding areas received.
“It’s called a snow-to-liquid ratio,” she said.
Generally, 1 inch of rainfall tends to yield about 10 inches of snow, which equates to a 10-1 snow-to-liquid ratio. Breaking it down further, one-tenth of an inch of water would produce about 1 inch of snow.
The below-freezing conditions, however, make it possible for 2 or more inches of snow to be produced with the same one-tenth of an inch of rain.
Friday’s high temperature in Hagerstown was 19.2 degrees, according to local weather observer Greg Keefer’s website, http://i4weather.net. The website showed that a total of 0.11 inch of liquid precipitation fell Friday, resulting in about 1.5 inches of snow.
“What ends up happening is ... a certain temperature, it creates what we call dendritic snow,” Beggs explained, saying that the snow crystals end up with air pockets between them rather than moisture, which makes them lighter and fluffy rather than wet, packable and dense. “It’s due to these temperatures aloft.”
Less overall moisture is needed to create significant snowfall accumulations in colder conditions, and it happens more quickly with temperatures below freezing, Beggs added.
Temperatures would need to be a bit warmer, usually in the 32-to-35-degree range on the ground, in order to produce the wet snow needed for making snowmen and hurling snowballs, Beggs said.
“So if temperatures were a few degrees warmer, that snow-to-liquid ratio would actually be lower and we wouldn’t be getting the higher amounts that we are in such a fast amount of time,” she said.
— Compiled by C.J. Lovelace
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