Nor'easter to bring chilly rain, snow to parts of New England

Snowfall in the mountains of the Northeast could accumulate to 5 inches.

A dip in the jet stream will direct colder air across the region Monday through Tuesday, as a slow-moving storm system that has caused widespread flash flooding across southern states finally reaches the East Coast and combines with another system coming out of the Midwest.

The developing system will gain strength off the East Coast and form into a weak nor'easter on Monday.

By Tuesday morning, the coastal storm will have strengthened further, bringing more rain, gusty winds and some high-terrain snow to parts of New England.

Parts of Pennsylvania, New Jersey, New York and Massachusetts could see another 2 inches of rain locally over the next 48 hours.

Meanwhile, snowfall in the mountains and higher terrain of the Northeast could accumulate to 5 inches.

ABC News' Morgan Winsor contributed to this report.