Where's Winter?

Where's winter?

As December 2012 begins, many Americans are asking themselves (and us) that question. While we've certainly seen some bona fide snowstorms -- heck, we've named two of them already -- there are parts of the country that haven't seen much snow at all.

(WINTER STORMS: Athena | Brutus)

For instance, Chicago, Milwaukee, and Des Moines have only seen a trace of snow so far this season. Normally snowy Grand Rapids, Mich., and Rochester, N.Y., had 0.3 inch of snow apiece as of Nov. 29, or just 4% of their normal snowfall through this point on the calendar.

(MORE: Chicago's Long Snowless Streak)

And even places that have seen a lot of snow are having trouble holding onto it. For instance, Great Falls, Mont., and Beckley, W.V., received well over a foot of snow from Brutus and Sandy, respectively. In both cases, the snow was all melted and gone within a week in a half.

We also haven't seen a lot of brutally cold weather, either. Yes, there have been the usual cold spells -- but mostly short-lived. Daily record highs outnumbered daily record lows by a 4-to-1 margin in November, according to the National Climatic Data Center.

That's made it tough for widespread snowfall to develop -- and in turn, the lack of widespread snow cover is one factor (among many) keeping temperatures relatively mild in recent weeks.

So what would it take for this pattern to change? Let's start with a recipe for extreme cold.

Recipe for Extreme Cold

If you want snow, you need cold air. And if you want the coldest air possible, you'd like to get some super-frigid air from the Arctic to come screaming south into the U.S.

We took a composite of three major historic Arctic outbreaks -- late December 1983, late December 1989, and early February 1996 -- to come up with a map that shows the optimal atmospheric setup for extreme cold across the United States.

The common thread is that there is always a strong northward bulge in the jet stream over the West Coast or the eastern Pacific Ocean.

On the eastern side of this bulge, the jet stream dives south, helping to drag bitterly cold air from Alaska and the Yukon south and southeast into the Lower 48. In these patterns, temperatures in the 20s below zero can drop into the Central Plains, and readings can flirt with zero even at the Gulf Coast.

(WATCH: What happens to boiling water at -22 degrees?)

Oftentimes this pattern manifests as a strong, brutally cold zone of high pressure at the surface; in fact, the highest barometric pressure on record in the Lower 48 (31.42 inches, or 1064 millibars) was set in Miles City, Mont., on Christmas Eve in 1983.

These extremely cold air masses tend to be shallow and stay close to the ground, so they can slip underneath the jet stream, unaffected by its strong winds, and plunge all the way south past the U.S.-Mexico border in the most extreme cases. The 1983 cold blast sent temperatures into the mid-teens in Monterrey, Mexico, and broke records from Montana to Texas to Florida to Pennsylvania.

But super-cold weather doesn't necessarily mean super-snowy weather -- how do we get that? Let's find out.

Winter Wonderland: An Easy Recipe

To get an idea of what a snowy winter looks like, you needn't look far -- we just had a doozy of a winter two years ago. The winter of 2010-11 put the word "Snowmageddon" on everyone's lips.

Of the many winter storms that winter, one stands out in terms of its geographic breadth. From the Rockies to the East Coast, the Groundhog Day storm was a prolific snow producer.

This snow depth map shows much of the U.S. had snow on the ground on Feb. 10, 2011, after a series of winter storms had swept across the country over the preceding two months.

(NOAA/NOHRSC)

Once again, we had a jet stream screaming south out of western Canada with plenty of cold air in place. (It didn't hurt that previous storm systems had left behind a robust snow pack across most of the northern U.S. already, keeping that air chilled as it spilled south.)

Powerful low pressure spun up along the jet stream, oodles of Gulf moisture streamed north to meet up with it, and bam! A massive swath of heavy snow fell from Texas to the Great Lakes to the Northeast.

(MORE: Blizzard photos | Classic Cantore thundersnow moment)

Tulsa, Okla., had its heaviest 24-hour snowfall on record, and Chicago had its third-heaviest snowstorm. The Groundhog Day blizzard was one of 2011's many billion-dollar disasters.

Deep snow cover often begets more cold weather, and this was a classic example. After this storm and another heavy snowstorm a week later, Nowata, Okla. (north of Tulsa) broke Oklahoma's all-time statewide low temperature record, reaching -31ºF on Feb. 10, 2011.

So now you know what it would take to get widespread frigid, snowy weather across the country. As of this writing, though, we don't see any signs of this pattern developing between now and mid-December, so any wintry weather is likely to remain fleeting and modest in scope.

(MORE: Warm Start to December)