(EDITOR'S NOTE: The National Weather Service increased the predicted amount of snow to 6 to 10 inches. WHDH Ch. 7, WCVB Ch. 5 and WBZ Ch. 4 are predicting up to 12 inches.)

Get ready, Sudbury ... this snowstorm means business.

The National Weather Service upgraded the winter storm watch to a warning earlier Saturday, and warned residents in the Metrowest area, including Sudbury, of wet, heavy snow that could accumulate anywhere from 6 to 10 inches.

"Rain is breaking out now and will soon transition to rain and snow," meteorologist Charlie Foley told Sudbury Patch at 3 p.m. "There will likely be higher totals just west in the higher elevations."

Gov. Deval Patrick has declared a State of Emergency in response to the impacts of the storm. Heavy wet snow combined with significant wind conditions has caused significant power outages throughout the state.

Snowfall rates could reach 1 to 2 inches per hour during the overnight hours.

The combination of heavy snow on top of branches that still have leaves on them could pose another problem.

"There could be some widespread power outages," Foley said. "The winds will be robust and we have concerns with leaves on trees. The snow on top of that could pull branches down on power lines."

Winds will shift to the north at 15 to 25 mph, with gusts up to 50 mph. Visibility will be anywhere from 1/4 to 1/2 mile. Traveling will likely be slow on well-treated surfaces, and quite difficult on any unplowed or untreated surfaces, according to the National Weather Service.

"It's unusual to have this type of snowstorm now," Foley said. "But we've seen it coming for a few days now."