A major winter storm is set to spread heavy snow and damaging ice across a large portion of the United States over the coming days. Dangerously cold temperatures will only worsen the storm and increase its danger.

In the Northeast, forecasts have called for 12 to 18 inches, though totals will vary locally and may be lower along the immediate coast. Mr. Lamers noted the potential for a “slowly pivoting snow band” to set up over the region; on the high end, localized areas could see two feet or more.

Weather maps show what you can expect for dangerous cold and heavy snow in the forecast for Boston this weekend.