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Why backs hurt and roofs collapse: Explaining snow weight ahead of the Colorado storm

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Posted at 4:41 PM, Mar 11, 2021
and last updated 2021-03-11 22:37:28-05

DENVER — Ahead of this weekend's snowstorm, we've had a number of questions about the weight of snow. This plays a factor in how much snow will fall during a storm.

The main thing that meteorologists look at to determine how much snow will fall is the ratio between inches of snow and the actual amount of liquid water. The higher the ratio, the lighter and fluffier the snow.

The typical ratio is a 10-to-1, meaning that 10 inches of snow is produced from one inch of liquid precipitation. This weekend, we'll likely see a heavier snow in that range, with forecasts calling for anywhere between 1.7 inches of water to 3 inches of water with this storm.

The "champagne powder" that our ski resorts like to brag about is sometimes a 20-to-1 ratio — really dry and fluffy! In the Midwest and the East, the warm, wet snowstorms can bring a slushy 6-to-1 ratio. That is the stuff that really gives shovelers a sore back.

Wet snow vs. dry snow: Hoping for some 'Colorado classic' this weekend

In the big storm of March 18-20 of 2003, the official Denver total for snow (as measured by the National Weather Service at a site near the old Stapleton Airport) was 31.8 inches of snow. Many other spots around the city had much more — up to nearly double that total in the foothills between 6,500 and 8,500 feet. The melted total for the storm was 2.80 inches for Denver's official total, so a little closer to an 11-to-1 ratio from that storm.

Now let's explain that a little further.

An inch of rain on an acre of land equals 27,000 gallons of water. The 2003 storm total of 2.80 inches means that the 31.8 inches of snow equaled 76,500 gallons of water on an acre. Since a gallon of water weighs about 8.33 lbs, that snowfall would weigh approximately 638,000 pounds per acre.

If you convert that over to tons, the total weight of the snow was about 320 tons per acre. That is for about 32 inches of snow, so for an average ratio of 10-to-1 or 11-to-1 snow/water ratio, the snow weighs about 10 tons per inch, per acre.

That might explain why your back hurt so much from shoveling and why all those roof collapses occurred, as well as the tree damage.

When storms set up just right to dump on Denver and the Front Range, they need to be in southeastern Colorado. A low pressure area stalled over southeastern Colorado will swirl moisture into the high plains all the way from the Gulf of Mexico!

This type of system acts as a funnel to bring all the moist air our way, press it up against the mountains and create a literal "snow machine."

Track Colorado's snowstorm in real time with the Denver7 24/7 weather stream:

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