Winter weather begins in earnest this week, as a fierce system pushes on a diagonal line from northeast to southwest Iowa carrying 4 to 6 inches of snow, with counties outside it likely to see at least 2 to 4 inches.

The National Weather Service put most of east and central Iowa on a winter storm watch from Monday night to Tuesday night.

The weather service predicts most of the snow will have fallen by Tuesday morning.

Waterloo, Des Moines and Fort Dodge comprise the triangle of heavy weather, which is the first serious storm of the season.

“Definitely in terms of impact, this is the most serious of the season,” said meteorologist Chris Legro of the weather service.

The weather service also warns of wind gusts, which could reach as high as 30 mph in central and eastern Iowa.

Light freezing rain was to begin late Sunday night in eastern Iowa and continue into Monday morning, before it mixed with falling snow.

Legro said the pattern of this system mirrors some of the 2007-2008 season’s nastiest storms.

Monday night, the threat of blowing snow has the weather service warning drivers about limited visibility.

“We’re looking at mixed precipitation, sleet, a wide range of factors hazardous to motorists,” Legro said.

In central Iowa, forecasters warn about snow accumulating to almost 8 inches by Tuesday.

The combination of wind, snow, ice and freezing rain make the oncoming system particularly hazardous, Legro said.

“It’s really quite the range of things,” Legro said.

Temperatures are expected to drop into the single digits statewide with the oncoming weather. By early Tuesday morning, the temperature should climb into the high teens or low 20s, and keep rising until it reaches highs in the low 30s by late Tuesday night.