(CNN) — Hilary strengthened into a hurricane in the Pacific Ocean southwest of Mexico on Thursday and is on track to pass along Mexico's Baja Peninsula. It threatens possible impacts in parts of the West as a weaker system.

Hilary is forecast to rapidly intensify through the end of the week into a Category 4 hurricane with winds of at least 130 mph, forecasters at the National Hurricane Center warned.

Thursday morning, the hurricane was about 320 miles south of Manzanillo, Mexico, whipping maximum sustained winds of 75 mph.

Hilary is expected to weaken significantly before it reaches Southern California and parts of the Southwest, but could potentially bring significant impacts to these areas in the form of heavy rain and flooding.

Daniel Swain, a climate scientist at the University of California at Los Angeles, said on Wednesday "multiple years' worth of precipitation" could potentially fall in some of California's driest areas.

With an uncertain forecast, a wide range of outcomes is still possible as Hilary will be moving parallel to the Baja Peninsula. Small deviations in the track will lead to significant shifts in rainfall amounts and impacts.

"This does have the potential to be a very high impact event for portions of Southern California," the San Diego National Weather Service said. "There is still a degree of uncertainty in the forecast and more details will come on exact timing, location, and magnitude of impacts in the coming days."