GRAY – The National Weather Service issued a winter storm watch calling for extreme wind chills through this morning and the possibility of significant snow Wednesday and Thursday.

A nor’easter was expected to bring the biggest snowstorm of the season to Maine, with 6 to 18 inches or more of snow predicted across the state.

Snow was expected to start falling Tuesday night in southern and western sections. Depending on the storm’s track, 6 to 18 inches could fall by the time it wraps up Wednesday night, said Butch Roberts, a forecaster in the weather service’s Gray office.

The storm will hit northern and eastern Maine on Wednesday afternoon and continue into Thursday afternoon, said Vic Nouhan, a forecaster in the Caribou office.

Depending on the storm track, those areas could receive 9 to 15 of inches of snow, with upward of 20 inches possible in localized spots, he said.

The weather service also issued wind chill warnings and advisories from Monday night through this morning across most of Maine.

The combination of cold temperatures and high winds is expected to drive wind chills to 35 to 40 below zero in far northern Maine and to 20 to 35 below in southern, central and western portions of the state.

Meanwhile, the cold snap continued across Maine on Monday, with temperatures failing to rise above the freezing mark in Portland for the 19th consecutive day.

The temperature hit 32 degrees in the early afternoon, but failed to go any higher.