All week, designers here have been enamored of special-effect snow. They've been churning up fake blizzards on the runway, hoping not only to create dramatic theater but also to give a sense of reality to the presentation. Here are winter clothes in winter weather!

But the garments here typically are based on fantasy and intellectual musings. They do not hold up well in a whiteout. Alexander McQueen, for example, had a model fighting a snowy windstorm dressed only in a blown-open kimono and white underpants. Karl Lagerfeld at Chanel used snow as a backdrop for his finale, in which the veteran model Pat Cleveland and her children paraded out in Chanel skiwear, followed by other models in miniskirts and short tweed jackets. But once the puffy flakes landed on the runway, they transformed into slick puddles of foam with an odor that hung in the back of one's throat like an itch.

The intent was to give folks a sense of how the clothes might work in the real world, where they also will be accosted by rain, sweat and a host of other indignities. Usually, however, the fake snowstorms made the clothes look like costumes in a middling stage production -- except at Y-3. Y-3 is designer Yohji Yamamoto's collaboration with the sneaker manufacturer Adidas. During his runway presentation last week, a wind machine was not only spewing flakes of snow onto the runway; it was also shooting white feathers into the air. But these clothes looked as though they could handle whatever nastiness the environment offered. The collection is founded on the basics of performance sportswear, on the idea that occasionally heels, makeup and a good tweed jacket are not enough to protect a woman from winter strife.

The collection accepts the fact that most women dashing through errands on a Saturday afternoon are wearing a pair of sweat pants, a turtleneck and a parka, rather than a box-pleated miniskirt, over-the-knee boots and a cropped shearling overcoat. In Y-3, Yamamoto deals in an often banal reality and attempts to give it a bit of polish.

He offers pull-on trousers with a slightly more structured shape and clean -- rather than droopy -- lines, butterscotch-colored parkas, heavy fleece hoodies, wool and leather letterman jackets and sneakers in metallic gold and silver. They are the clothes that folks wear despite their best intentions to look a little nicer during their non-work hours.

This sort of clothing is rare on the runways here. Most designers in Paris believe that their mission is not to enable the woman who styles her hair by putting on a baseball cap, but to elevate her aesthetic sensibility by showing her the beauty of, say, a mink-trimmed business suit. When designers have put track suits on the runway in the past, they felt compelled to jazz them up by trimming a hooded sweat shirt in fur or by stitching the pants out of gold lame{acute}, transforming them into an ensemble more complicated and rigorous than what one might be inclined to wear to the farmer's market.

Rarely do designers in Paris talk about the reality of how women dress when left alone to confront the contents of their closets. Designers here do not mix mink jackets with faded bluejeans. Bike messengers have inspired New York designers. Designers in Milan have looked to homemakers, fruit vendors and uniformed bureaucrats. That occurs infrequently in Paris, where inspiration typically derives from intellectualizing fashion history or popular culture. Rarely is the explanation for a design as mundane as: I noticed that women like to wear their cardigans hanging loose, so I didn't put any buttons on my sweaters.

The simplicity of Y-3 loudly contradicts that tradition. It validates casualness in both theory and practice. It celebrates the dirty secret that French women -- despite their reputation for relentless chic -- do wear sneakers with their pants.

Lanvin Designer Alber Elbaz works from the more traditional school of thought. Birds inspired his collection for Lanvin. While he may not be thinking about the most mundane aspects of a woman's life, he is respectful of her curves and her desire to be comfortable. His signature pieces for fall are dresses pleated all around, but in contrasting colors from front to back and belted with satin ribbons.

They are gentle, fluid clothes. They did not need the feather flourishes that were added to underscore the bird theme but that ultimately played like heavy-handed silliness. Elbaz has an enviable light touch. He excels at unfinished edges, the sweet placement of a ribbon or the sly angling of a brass zipper. He appears to be less comfortable with glittering sequins, such as those forming the pattern of a bird on the back of a dress. His wonderfully delicate dress is weighed down by a silver and bronze bird perched between the shoulder blades.

Elbaz does not make declarations from the atelier. But he embraces the notion that the designer should elevate the taste of a client. He should provide her with something that she has not considered. She may be welcome to break the rules and to go her own way, but it is the designer's job to set the tone of the aesthetic conversation.

Stella McCartney Stella McCartney's collection is distinguished by its keen understanding of the way in which young women dress, with their desire to mix a pair of jeans with a vintage blouse, to toss on a tailored suit with a T-shirt or to slip into a sexy satin skirt with a jacket that takes its inspiration from a sporty windbreaker. She advocates for making her "chick style" part of the formal fashion vocabulary.

But on the runway, McCartney's collection looks disjointed. For fall, there are some splendid pieces such as corset tops with carefully detailed decoration. But they are paired with satin skirts that often do not fit the models well -- they tend to bunch up around the hips as the women walk. But when the skirts fit, one can appreciate the intricate seams and the inside-out illusion created with opposing textures.

The pencil-slim silhouette below the waist is contrasted with filmy blousons that have a way of looking sloppy on the runway. They never look as nonchalantly hip as when McCartney herself comes onto the runway wearing one to take her bows. These tops, if they are to be worn to maximum effect, require a certain individual cool. Her models, unfortunately, lacked that. McCartney is her own best advertisement for laissez-faire chic. And her collection is evidence that real-life style can be more challenging than fantasies.

Previous stories and photo galleries from the fall fashion shows are available online at www.washingtonpost.com/wp-srv/style/fashionshows.html

Practically perfect: Yohji Yamamoto's Y-3 line, heralded with special-effect snow and feathers, features clothes to suit real weather.Stella McCartney's designs require a certain cool to pull off; alas, her models lacked her signature nonchalance.Pleats, thank you: Alber Elbaz's designs for Lanvin revealed his light touch with gentle, fluid shapes, and his attention to comfort as well.