BOSTON -- A deep freeze will turn into deep snow as a massive storm moves across New England starting Saturday afternoon.

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The National Weather Services says that by sundown, the storm is expected to track southeast of Nantucket, with snow starting across western Rhode Island and Southern Worcester Country this afternoon.

It is forecast to bring blizzard conditions from the Interstate 495 corridor and the Massachusetts Turnpike to the south coasts of Massachusetts and Rhode Island.

A blizzard warning will be in effect from 5 p.m. Saturday afternoon to 6 p.m. Sunday.

Forecasters say a powerful nor'easter will deliver a one-two punch of heavy snow and strong winds lasting into Sunday morning. The storm has the potential to produce near-blizzard conditions from the Route 95 corridor to the Cape and Islands.

At the height of the storm, snow may be falling at rates of 3 inches an hour.

Motorists across southern New England are being urged to complete their travel plans by Saturday morning, or postpone travel until Sunday afternoon.

Six to 12 inches are expected in Boston and points west, with upward of 1 to 2 feet south of the city and across southeastern Massachusetts, Cape Cod and the Islands.

Clouds will increase across the region and snow will develop across southwestern New England by late Saturday afternoon and then spread throughout the rest of southern New England during the early evening. The snow will become heavy quickly.

Blizzard or near blizzard conditions will affect all of Connecticut, Rhode Island and much of Massachusetts Saturday night into Sunday.

Snow will fall at a rate of 2 to 3 inches per hour at times Saturday night and be accompanied by winds gusting to 50 mph in the interior and to 60 mph or more along the immediate coast.

Travel is likely to become downright dangerous across southern New England Saturday evening and remain so into Sunday morning. Anyone with plans that include travel should ensure that they are completed by dark Saturday.

Accompanying wind chills well below zero can mean life-threatening conditions for anyone who becomes stranded Saturday night or Sunday morning.

In addition, a storm surge of around 3 feet and waves of 20 to 30 feet just off the east coast will result in coastal flooding along the Massachusetts east coast around the Sunday morning high tide. A number of shore roads will likely become impassable for a time Sunday morning.

The powerful storm will develop off the mid-Atlantic coast late Saturday and pass just southeast of Nantucket Sunday morning.

Despite the recent cold snap, state officials are still warning about the dangers of thin ice on area lakes and ponds.

Massachusetts Emergency Management Director Cristine McCombs said fluctuating temperatures make ice conditions uncertain for skating, ice fishing and other winter sports.

Instead, people are urged to use recreational skating areas provided by various cities and towns.

If you do venture out onto pond and lake ice, MEMA is issuing the following tips: Never go out on the ice alone, keep pets on a leash and beware of ice covered with snow.

The snow can insulate the ice from fully freezing.

Officials also say that ice forming over flowing waters like lakes and rivers is generally 15 percent weaker.