Wednesday, January 04, 2012

The National Snow-Cover Problem

2010: 58.1%
2011: 47.8%
2012: 21.7%

The numbers above represent the percentage of the Lower 48 covered in snow on January 4th of those respective years. I think one thing a lot of people fail to really appreciate about the last couple of winters is just how widespread and significant winter weather was on a national level...not just in the Eastern US or even just the Northeast. Winter came and it hit a LOT of people hard the last two years.

The simplest way to look at this is with temperatures and how different 2011-12 has been from 2009-10 and 2010-11. But the most interesting, in my opinion, is to look at snow depth. In the interest of full disclosure, I got the idea for this from a weather blog in Southern Louisiana at KLFY-TV in Lafayette. 

Three maps are posted below for you...with the snowpack from January 4th in 2010, 2011, and now 2012. While the numbers above are impressive, the maps are even moreso.

2010
Click to enlarge (Image Credit: http://www.nohrsc.noaa.gov/nsa)


In 2010, snow cover was incredibly widespread, with coverage all the way south into Mississippi, Arkansas, and Oklahoma, and plenty of mountain snow in the West...especially California and the Cascades. Almost every location north and east of about Oklahoma City, OK had snowpack on January 4th, 2010. 58% is a strong number for snowpack.

2011

Click to enlarge


In 2011, the map is somewhat deceiving. Had I gone back 3 or 4 days, over 50% of the country would have been covered, but with the melting of the Boxing Day Blizzard, only 47.8% was covered in snow. Still, it's extremely impressive, especially when you look at how much snowpack had been laid down in the Sierra, Northern Rockies, and Cascades out west. They got crushed for awhile last year, and even down south into Arizona and New Mexico saw a very frontloaded winter. The Dakotas and Minnesota saw quite a bit too, and of course, this foretold the story of epic flooding in some of those areas that subsequent spring. So 2010 was great for snow lovers, 2011 was solid, then what of 2012?

2012

Click to enlarge


"Anemic" describes it best. And again, this is on a national level. The snow cover you see in the Great Lakes and Appalachians was barely there as of a few days ago. We're at 21.7% of the country covered in snow now. A couple days ago, we were sub-20%. While the aerial coverage certainly is a stark contrast to the last few winters, note some of the more striking changes....out West. Things are a little better in New Mexico and Arizona than is normal, but it's all mostly confined to the high terrain. It's hit hard in spots out in those areas and further north, but it hasn't really gone widespread. California is hurting terribly this winter. After a great 2010 and an almost Biblical 2011, 2012 has been horrendous for ski resorts an'll d water supply. Thankfully, there was enough in 2011 to carry over into 2012 for water supplies, which is great news. But California snow water equivalent is at 19% of normal, over the entire Sierra! 

The US has been flooded by Pacific air and mild conditions all winter. At best, cold air intrusions have been brief and not with much moisture. Most of the snow has fallen, as you can tell, up in British Columbia, even a little moreso than the last couple winters. Alaska has been frigid, with incredible cold. That's a tell-tale sign of problems getting widespread snow and winter in the Lower 48...and until that breaks down, the snow drought continues. Until that breaks down, I say? As you'll be hearing more about in the coming days I'm sure, that may finally be in the process of actually breaking down. Tom will have more on this possible change for you tomorrow. 


The national snow drought might not last the entirety of winter, but the first half has certainly been something impressive!