What's that brown layer in the snow?

by Kyle Cooke • Published on March 15, 2021

DENVER — Over the weekend, Denver received just over 27 inches of snow, making it the fourth largest snowstorm in the city’s history, dating back to 1881.

The airport closed, buses and trains stopped running, and Denver students were rewarded with a snow day. On Monday came one of the not-so-fun parts: people digging their way out of the snow.

Shovels in hand, they may have noticed, under all those inches of snow, a thin brown layer at the base of their patio furniture, tree branch, or whatever other object they were using as a reference point.

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I’m seeing some dust/aerosol deposits in the snow here in Fort Collins. Any idea where this is coming from @russ_schumacher @NWSBoulder? Location is one mile SE of Old Town FC. pic.twitter.com/ox7ADui1RV
— Tom Cram (@ThomasCram) March 14, 2021

According to the National Weather Service (NWS), that brown layer of snow isn’t actually snow at all. It’s dust, and it traveled all the way from Mexico.

Check it out! We received a few comments that people saw a brownish layer in the snow and we were able to capture a picture of it here at the office. This is actually a layer of dust transported from Mexico! @NWSAlbuquerque pointed it out on satellite last night. #COwx https://t.co/XOTm74f87c pic.twitter.com/c5rdlyMRiR
— NWS Boulder (@NWSBoulder) March 15, 2021

As the NWS Albuquerque branch pointed out, the dust traveled from playas, or beaches, in Mexico.

Epic dust storm from northern Chihuahua, west Texas, and southeast NM this afternoon (Mar 13). Wind gusts 55 mph in Artesia. Interesting dust plume trajectories too. #duststorm #AirQuality #drought pic.twitter.com/HkfwYujZOS
— Dave DuBois (@NMClimate) March 14, 2021

The dust even showed up in the NWS Boulder office's snow sample after it melted.

Thankfully, the dust traveled high enough not to affect visibility on its way through New Mexico and into Colorado.