Tuesday promised to be the worst travel day yet from a late-season winter storm that’s forced the cancelation of nearly 8,000 flights since Sunday.

Sea-Tac Airport reported at least two-dozen flights canceled as of 6 a.m. Tuesday. Check flights at Sea-Tac

Airlines moved quickly to pare their Tuesday schedules ahead of the storm, which had been forecast to bring crippling conditions to much of the Northeast. Airlines preemptively axed 5,300 flights for the day, all before midnight Monday, according to flight-tracking service FlightAware. More than 100 additional Tuesday flights been canceled as of 6 a.m. ET, a figure that was likely to keep growing even though snow totals were falling short of initial estimates in Philadelphia and Washington.

Nearly all flights were canceled at the three big airports serving New York City, which remained under a blizzard warning for much of Tuesday. Few flights were expected to operate at JFK, LaGuardia and Newark Liberty airports, and similar problems were likely at smaller airports across parts of New York state and New England.

It was a similar story at Boston and Baltimore, where most of Tuesday’s flights had already been canceled before the day even began. Three of the region’s other major airports – Philadelphia, Washington Dulles and Washington Reagan National – also saw major disruptions, with between 30% and 50% of the day’s schedule preemptively canceled, according to FlightAware. Even Chicago was seeing storm-related cancellations continue for a second consecutive day, with about 320 at O'Hare as of 6:40 a.m. ET and another 100 across town at Midway Airport.

Wednesday was expected to see some recovery, but carriers were already canceling flights. More than 635 flights were grounded before the end of Monday and more were likely as airlines tried to restart their operations.

“We expect this number to rise considerably for Wednesday morning as airlines get their operations back online,” FlightAware CEO Daniel Baker said in a Monday evening statement.

The speed of the recovery could depend on whether the storm is as bad as forecast. While up to 18 inches were forecast across much of the region, some forecasts began to suggest rain may mix in and depress snow totals – as was the case in Washington and Philadelphia.

Still, winds of up to 50 mph across New York and New England were likely to compound flight problems created by the snow.

KING 5's Travis Pittman contributed to this report.