Welcome to Weather Math 101.
1 Strong La Niña + 1 Insane Arctic Oscillation
= 1 giant blizzard for 100 million people
Groundhog Day arrived and instead of a photogenic rodent, we got a 2,100-mile-long blizzard. One third of the nation is being slammed by a huge storm that stretches from New Mexico to Maine.
Click to enlarge photo  and find the hidden nation!
The Groundhog Day Blizzard buries the USA
If you live in a city, you are being buried in snow and traffic is paralyzed. If you are in the country, you are desperately trying to protect your livestock and worrying about your winter wheat crop. You probably don’t care if a dozen groundhogs saw their shadow.
Eastern groundhogs tend to be more likely to see their shadows during an El Niño and as several readers of the last blog noted, this is a La Niña year. Poor Punxsutawney Phil probably needed a snow shovel to get out of his burrow. When he did, there was no shadow.
So what do La Niñas do – besides creating wretched woodchucks? Typically La Niñas are cold weather events. Over a million square miles of abnormally cool water develops in the Tropical Pacific. This cools the tropical air mass overhead which in turn changes air pressure patterns and winds. With that much cooler air, wind and weather patterns are changed all over the globe.
Here in North America, cold weather builds up over the Northwest. As winter progresses, the cold expands eastward. In a strong La Niña, like the one we have this winter, the cold reaches the Northeast by mid-winter AKA February 2.
Typical January–March Weather Anomalies and Atmospheric Circulation During Moderate-to-Strong La Niña.
Unfortunately, we are not just dealing with La Niña; we also have a wildly fluctuating Arctic Oscillation. In December, it was dramatically negative, allowing cold polar air to plunge to Florida. Now it is sharply positive (over +2.0), allowing warm air from the Gulf of Mexico to waft north. The cold air in the north, with wind chill, may be below zero, but parts of the Gulf are in the 70°s.
The La Niña weather pattern is allowing the cold air to smash into the warm, wet air. Think of a car crash – it’s not pretty. Two giant air masses crashed and we are in the middle. Ugh!
And the groundhogs don’t like it either.
Tell us about what the storm is doing in your area. I have 18 inches of snow and I live 300 miles from the Mexican border!
Evelyn Browning Garriss, historical climatologist, is a longtime writer for The Old Farmer's Almanac. She is also editor of The Browning World Climate Bulletin  and has advised farmers, businesses, and investors worldwide on upcoming climate events and their economic and social impact for the past 21 years.