Monster winter storm and Arctic blast loom over the U.S.; Boston braces for extreme cold.

A two-part weather setup could merge into a major winter storm and Arctic outbreak across the U.S., bringing a heavy snow swath (about 1–2 feet) for parts of the country and a hazardous ice threat to the South; Boston’s forecast remains uncertain with the potential for limited impact, but the weekend will bring the coldest air of the season as models continue to shift over the next 48–72 hours.