"We are having really crazy weather this winter," meteorologist Jeremy Davis told OnTheSnow.

Folks in Florida, London, Paris, and elsewhere would agree.

Davis said a northward flow of warm air into the Arctic appears to be driving a southward flow of cold polar air that is wreaking havoc with the norms across North America and Europe.

He said the current weather is likely a result of La Nina, which acts as an air circulation pump, combined with melting Arctic sea ice, which allows milder air to flow north and colder air to flow south.

The result is great volatility in weather, he said, which on the ground translates to deep snow in the high peaks of the Sierras even in Southern California, cold and snow across the Midwest, cold up and down the East Coast, freezing temperatures in Florida, and snow and cold across Europe.

"A lot of warm air is flowing up toward Arctic by Greenland and Eastern Canada, dislodging the colder air in the Arctic and sending it south. Most of that is occurring in two places: Central and Eastern North America, and Europe. Europe and Siberia have been really cold. They've had snow in England and Paris. That's really something.

"They do get cold outbreaks, but not much. You think of Victorian scenes of England, Currier and Ives prints of snow in London, ice skating, Scrooge walking through snow, but that was all in a colder period in the 1700s and 1800s. The last two years there has been a lot of cold air in Europe and the U.S., and lots of major snowstorms in the Mid Atlantic," Davis said.

We caught up with Davis this week on the slopes of Wachusett Mountain Ski Area in Princeton, where he learned to ski as a boy, along with his brother, Nate.

He made 22 runs in four hours for a total of 17,700 vertical feet. Davis keeps track of such things, and of New England ski history as well. He founded New England Lost Ski Areas Project, a Web site that chronicles regional ski lore and minutiae of ski areas that are no more.

His day job is as a meteorologist in Syracuse, N.Y., and he relishes opportunity to talk about the weather and climate.

"This is a really interesting weather pattern.

"One theory is that a reduction in Arctic sea ice is breaking up the usual temperature gradients we have north to south, allowing milder air to go north and colder air to go south. It's such a recent phenomenon that it hasn't' really been explored as much.

"It's one of those laws of unintended consequences with climate change, we don't always know what's happening.

"How long with this current weather pattern last? Who knows. It's too early to tell. It could warm up later in the winter, or stay cold right through. The next two weeks will be colder, with below normal temperatures and good chance of snow.

"This weekend there's a Nor'easter off the East Coast of North America, but the models are all over the place," he said.

The National Weather Service forecast for Southern New England mid-day Friday, Dec. 17, reflected this uncertainty, in spades: "A winter storm remains possible late Sunday into Monday however storm track and intensity remain uncertain at this time. Latest indications suggest the greatest risk for substantial snowfall and strong winds will be across Eastern Massachusetts and Rhode Island ... Unfortunately there is too much uncertainty at this time to provide details on snow amounts. Stay tuned to later forecasts for updated information."

"I wouldn't be surprised at anything that happened," Davis said, "from plowable snow, to next to nothing. It's really all over the place. I haven't seen this type of uncertainty for awhile, with every single forecast model all over the place. We'll find out soon enough."

He returned to a general discussion of the season's weather.

"The West Coast is getting hit by a lot of weather fronts, driven by La Nina. The Sierras are getting a lot of snow, with the current forecast calling for the high peaks getting up to 10 feet of snow. La Nina has its strongest effect in the Pacific Northwest. It's unusual for La Nina to be so intense farther south in California, but that's what is happening this winter.

"La Nina adds a lot of variability across the continent. The biggest thing we can expect this winter is just that: a lot of variability. Lots of periods of cold and storms, then periods of warm and rain. This winter should be pretty volatile.

"The weather pattern has the big thrust of cold air pulled down across the Midwest, and onto the East Coast. This winter it's moved down to Florida and that's really something. The cold they've had this past week has been outlandish even from them," Davis said.