SEATTLE — YOU could chalk it up to ''Northern Exposure,'' the boom of Seattle ''grunge'' rock music, or even the proverbial livability factor.
But more likely, it comes down to money.
Seattle is playing host to Hollywood productions at an increasing rate. This spring, the buzz is about Sylvester Stallone, who is in town for two months filming ''Assassins,'' a futuristic thriller. The pectoid-pumped star, known for his macho roles as ''Rocky'' and ''Rambo,'' describes his latest character as ''very cerebral.''
Though a popular grouse among residents of the region is about being overrun by Californians moving north, folks have greeted the film crews mostly with open arms. And Seattle, Portland, Ore. and Vancouver, British Columbia, are gearing up to see who can best woo Hollywood's movie-making dollars.
''It's rather exciting, ... especially in the downtown where it's been kind of lonely,'' says Louise Avery, concierge at the US Bank Center. ''We all think we're best friends with the guy,'' she says of Mr. Stallone.
The visitors from Hollywood feel just as warmly. ''I would live here in a second,'' says John O'Connor, part of the camera crew.
''I miss the smog,'' comments his colleague Vince Mata. Other than that, he says, the area is great.
Prior to the 1970s, Washington State was a backdrop in a handful of films, including ''Call of the Wild.'' Also shot here in 1989, 'The Fabulous Baker Boys'' and last year, ''Disclosure.''
The latest spurt in Hollywood interest is fueled by the opening a film office and the success of television productions such as ''Northern Exposure.'' When a TV series, with its tighter profit margins, finds a hospitable home here, movies follow, says Richard Woltjer, publisher of local film industry guide.
Joel Silver, producer of ''Assassins,'' says the region is an attractive because of its blend of relatively low costs, proximity to Los Angeles, and variety of scenery, from big-city to the wilderness. The city also has a top-quality film-processing lab and sound stages in former Navy air-base hangars.
Seattle Mayor Norm Rice hopes that luring film companies here regularly could help revitalize an urban center that has seen jobs and retail business flowing to the suburbs. The Hollywood crowd not only spends money on everything from hotels to lumberyards, but movies also lure tourists.
''When you get a picture post-card [film] like 'Sleepless in Seattle,' '' the promotion impact is greater than any tourism office could conjure up, Mr. Woltjer explains.
Rice and the private Washington Motion Picture Council share a goal of seeing out-of-state film spending here grow from $55 million last year to $200 million by 2000. Getting there will be a competitive process.
Almost all states have film offices, and ''we are located between these two guys who have a phenomenal competitive advantage,'' Woltjer says, referring to the cities of Vancouver and Portland, Ore. Portland has outspent Seattle on marketing, and Oregon has no sales tax, while Vancouver has benefited from exchange-rate shifts between the US and Canada.
The local film industry is lobbying the Washington State Legislature for a targeted sales-tax break that would exempt film-industry spending (but not food and lodging costs) from the 8-percent local sales tax.
While some locals worry about explosions rigged for ''Assassins'' action scenes, others are not so concerned. One suggests demolishing the notorious Alaska Way viaduct, which blocks many city buildings from a waterfront view.