It was notable but unnoticed during Washington’s in­cred­ibly snowy winter of 2010: People got used to snow.

By the time the third big snowfall threatened on Feb. 11 — after earlier snows of 17.8 inches and 16.4 inches — the panic to buy milk, bread and toilet paper subsided. People came to accept snow as a winter fact of life, much as they do in Chicago or Buffalo or Boston. They just got out there and shoveled.

But memory is as fleeting as a butterfly, and with the first significant snowfall this winter likely to fall Tuesday — perhaps as much as six inches, maybe more — the region embraced the fear and loathing common when winter weather gets nasty.

After a temperature tease near 60 degrees Monday, it seemed implausible that frigid, snowy weather might arrive by Tuesday afternoon, but the Post’s Capital Weather Gang explained the pattern.

“An arctic front is advancing south and east, and temperatures will steadily drop to below freezing by dawn,” the gang’s forecasters said. “If temperatures end up a little warmer than forecast or are a bit slow to cool, we might lose a little accumulation to melting early on in the storm, but we’ve factored that into our forecast and feel confident that enough cold air and enough moisture will arrive to overcome [Monday’s] warmth.”

The National Weather Service issued a winter storm warning for the region.

What that means for schoolchildren is anybody’s guess, except for students in Arlington and Montgomery counties, who already have the day off for what educators call a “professional day.” Other school officials consulted with their weather experts, in the seasonal quandary posed by the risk of putting school buses on the road with snow in the air.

Throughout the region, crews spent Monday treating major roads with the briny mix intended to slow the buildup of ice when snow begins to fall.

In the District, Department of Public Works Director William O. Howland Jr. said he planned to have 200 plows prowling the roadways by 8 a.m. Tuesday, with plans to keep them in snow-assault mode until the flakes stop falling Tuesday night.

“We expect to work at least two 12-hour shifts, possibly longer, since the forecast is for temperatures well below freezing,” Howland said. “The operation began Monday when crews applied a solution of brine and beet juice to bridges, other elevated structures and challenging streets to reduce the possibility of ice forming.”

He said that once the snow starts, crews will spread salt until enough snow accumulates to require plowing.

In Maryland, state officials planned to direct their forces from the state operations center near Baltimore-Washington International Marshall Airport.

“Please put safety first by planning now for driving conditions tomorrow,” said Melinda B. Peters, head of the State Highway Administration. “We expect this storm to affect travel for most of the day, including both the morning and evening commutes. Please allow extra time and reduce speeds, especially while precipitation is still falling.”

Drivers were urged by AAA to keep an emergency kit in their cars.

“The warning does extend from 7 a.m. to 11 p.m.,” said Lon Anderson of AAA. “Drivers who must venture out should make sure their vehicles are prepared and to drive cautiously and defensively.”