Hurricane Lee continues to churn north as a large and powerful storm over the open ocean. The forecast track has shifted west over the past two days, increasing the risk of tropical storm and hurricane conditions in eastern New England late Friday into the weekend.

On Wednesday evening, the National Hurricane Center issued a hurricane watch from near Bar Harbor, Maine, to the Canadian border and a tropical storm watch along the New England coast south to near the Rhode Island-Connecticut border.

"Tropical storm conditions are possible over a large portion of coastal New England, including Cape Cod, Nantucket, Martha's Vineyard, and Block Island," the National Hurricane Center wrote.

The Hurricane Center also warned that "life-threatening storm surge flooding" could occur in southeastern Massachusetts, including Cape Cod and Nantucket, late Friday and Saturday, where it issued a storm surge watch. The surge is the wind-driven rise in ocean water above normally dry land.

Currently, the storm is set to mostly spare the southeast and Mid-Atlantic adverse impact, although dangerous surf and rip currents are expected at the coast.

Ahead of any impact in the Northeast and Atlantic Canada, a tropical storm warning has been issued in Bermuda, where Lee will deliver gusty winds of 40 to 50 mph and squally weather Wednesday night into Thursday. From there, it becomes a question of how closely Lee will hit New England.

There are three main scenarios that appear on the table at this point. Here, we break them down and outline different outcomes.

The overarching weather pattern

While Lee has begun to weaken, it is an usually large and dangerous storm. Its peak winds dropped from 115 to 105 mph Wednesday evening, but its wind field was becoming larger. Think of an ice skater outstretching their arms while spinning - they would slow down, since they're tracing bigger circles. Same thing with Lee. It's now a bigger storm, but maximum sustained winds are diminishing some.

That expansion of Lee's wind field will churn up cooler waters from below the sea surface, hastening the weakening of its winds. By Friday, it will also begin to transition into a nontropical storm, tapping into jet stream energy and changing its structure.

That, however, means an even farther expansion of the storm's wind field. That's why areas from southern New England to Halifax, Nova Scotia, are expected to face rough conditions. The bigger storm, moreover, will pile more water against the coast, leading to a bigger storm surge.

The biggest wild card at this point is how far west Lee gets tugged by an approaching upper-level trough, or pocket of high-altitude cold air, low pressure and spin. Recent computer model guidance has indicated a farther westward bend of the track. We discuss that scenario below.

Scenario 1: Close to the 'official' National Hurricane Center cone

Assuming Lee takes a track close to the National Hurricane Center's projections, conditions in southeastern Massachusetts, the Cape and the islands, as well as Rhode Island, will deteriorate Friday night. The worst will come Saturday morning when winds on outer Cape Cod could gust 55 to 65 mph, with 30 to 40 mph winds along the Massachusetts east coast and a few gusts to 50 mph on Cape Anne.

Most of coastal Maine and the New Hampshire Seacoast would see gusts of 40 to 50 mph, with a few 55-to-70-mph gusts in Downeast Maine.

All those areas, on the west side of the system, will see an offshore wind - other than the inside of Cape Cod, where a 2-to-4-foot storm surge would be possible in Barnstable and toward the Mid-Cape.

On the right side of the system's center, onshore winds would bring a 3-to-5-foot surge in Nova Scotia. Winds could gust upward of 75 mph at the coast.

Regarding rainfall, an inch or two would be possible in coastal New England, with 3 to 4 inches in Downeast Maine and 4 to 8 in Nova Scotia.

Scenario 2: What happens if Lee tracks more offshore?

A farther offshore track would relegate tropical storm conditions to the immediate coastline in southern New England, with a few gusts of 45 to 50 mph on Cape Cod. Boston and Providence wouldn't see much. Rainfall amounts would walk a tight gradient and taper off quickly inland.

In the Gulf of Maine, gusts up to 35 or 40 mph would be possible, with a few gusts to 45 mph in Downeast Maine. A more direct hit in Nova Scotia or even farther east would bring stronger winds there, but surge impacts would depend on where the storm's center tracked.

Most of interior southern New England would be mostly dry.

Scenario 3: The storm could hit Gulf of Maine/Downeast Maine.

If the storm swings even farther west than anticipated and makes landfall in the Gulf of Maine, winds of 70 to 85 mph would occur near the landfall zone. Most of coastal southern New England and Nova Scotia would see gusts of 65 mph or greater, with gusts over 75 mph on Cape Cod and in Downeast Maine.

A general 4 to 8 inches of rainfall would occur close to and just west of the center's track, affecting Maine.