The 2016 BMW 340i sedan. (BMW/ )

Freshly fallen snow is magical when light and powdery. It supports the romance of a “white Christmas” and is great for TV commercials for all-wheel-drive automobiles.

According to the ads, you can drive through snow in those cars without slipping, sliding or helplessly spinning drive wheels.

They are great pitches for models such as the 2016 BMW 340i xDrive sedan, which is one of the best-built, best-performing midsize sedans sold anywhere.

But the 340i xDrive is no match for Mother Nature when she decides to cover your world with two to 3 1/2 feet of snow. For one thing, the math doesn’t work.

This month’s blizzard dumped as much as 42 inches of snow on parts of the Mid-Atlantic and Northeast. BMW’s 3-series xDrive models (the wagons) are built on platforms with a ground clearance of 8.3 inches. The 340i xDrive sedan has a much lower ground clearance — 5.7 inches. Who has the upper hand in that situation? You or Mother Nature?

So you do what I did — obey authorities and give snowplow crews a chance to reasonably clear roadways, except that your definition of “reasonable” and theirs could be considerably different. No matter. You have a 340i xDrive sedan. You think you can go.

And you can go — on the plowed roads that are more in compliance with your definition of “reasonable.” Unfortunately, two days after the biggest snowstorm in recent regional history, those roads don’t include your street.

But you are grateful for the work your wife and terrific neighbors did freeing your car from massive snow mounds and removing the icy mess from your long driveway. You and your injured back are elated at that good fortune. You are eager to get on the road with the BMW 340i xDrive — “xDrive” being the designation for the manufacturer’s all-wheel-drive products.

Everything goes well at first. You can feel the drive power shifting from slipping wheels to gripping wheels, exactly the way BMW’s “intelligent all-wheel-drive” system was engineered to work. But you become overconfident, buoyed by your initial success and the “go anywhere” message of those TV commercials. You turn right and head uphill, unaware that huge lumps of snow have been shoveled into the middle of the street.

You get stuck. Overnight, Mother Nature has exercised more of her power. The snow, once light and powdery but now frozen mush, has become more problematic with hidden sheets of traction-resistant ice. Forget the automatic changing of drive power from slipping to gripping wheels. Every wheel is slipping. You are going nowhere.

Neighbors emerge and shovel you out. Thank God for them. With their help and advice, you manage to turn the 340i xDrive around and point it downhill, letting gravity and all-wheel drive work with Mother Nature. You roll downhill toward a major road that is truly reasonably plowed.

You learn something from the experience. One: Human arrogance encourages us to embrace themes such as “The Ultimate Driving Machine” and “Don’t just drive. Conquer.” Two: It is important to have and keep good neighbors. Three: TV commercials, no matter how well produced or photographed, are no substitutes for common sense.

There is something else: The 340i xDrive is a very good sedan. It is well crafted, smartly designed and technologically brilliant. The all-wheel-drive system works quite well when intelligently used.

I got stuck on/in ice because I was stupid. The all-wheel-drive competence of the 340i xDrive, used in conjunction with common sense and neighborly help and good advice, got me unstuck.

And this: Automobile manufacturers — and here I’m thinking BMW, Jeep and Ford — need to stop telling consumers that their vehicles are “unstoppable” in dangerous weather, or that they can get through any inclement event because of the power and overall engineering of their vehicles. The truth is, they can’t. Believing that nonsense only leads to trouble.

Nuts & Bolts
BMW 340i xDrive

Bottom line: The 2016 BMW 340i xDrive sedan is part of a family of 3-Series vehicles that have been global bestsellers since their debut in 1975. There is a reason for that. They work extremely well, but they must be driven wisely in the snow.

Ride, acceleration and handling: It gets excellent marks in all three categories on dry or moderately compromised roads. Hint: Get rid of summer performance and run-flat tires often offered as original equipment on 3-series models. The benefits those tires provide in dry weather can turn them into albatrosses in winter.

Body style/layout: There are modest changes for 2016, including a redone front end with LED headlamps. The mid-size, front-engine luxury sedan was formerly sold as the 335i. The name change was occasioned by the installation of a new six-cylinder engine. The 340i is available with rear-wheel drive or all-wheel drive (xDrive).

Engine/transmission: The 340i xDrive comes with a 3-liter, twin-turbocharged (forced air), in-line six-cylinder, 24-valve gasoline engine with variable valve timing. The engine, linked to an eight-speed automatic transmission, delivers a maximum 320 horsepower and 330 pound-feet of torque.

Capacities: Four adults fit comfortably. Cargo space with all seats in place is 13 cubic feet. The fuel tank holds 15.8 gallons (premium gasoline is required).

Mileage: I spent so much energy slipping, sliding and spinning, real-world mileage was hard to pinpoint. The Environmental Protection Agency estimates 22 miles per gallon in the city and 33 on the highway.

Safety: Standard equipment includes four-wheel ventilated disc brakes; four-wheel anti-lock brake protection; automatic emergency service notification; air-bag deployment notification; post-collision safety system; stability and traction control; side and head air bags; and stolen-vehicle tracking.

Pricing: The 2016 BMW 340i xDrive sedan starts at$47,800, with an estimated dealer’s invoice price of $45,300. Price as tested is $59,920, including $9,000 in options (including advanced electronic safety and driver assistance systems) and a $995 factory-to-dealer shipment charge. Estimated dealer’s price as tested is $56,000.