(This article, initially published Wednesday midday, was updated in the evening and at night to reflect the latest information from the Central Pacific Hurricane Center.)

The extremely powerful Hurricane Lane is closing in on Hawaii, where torrential rain, strong winds and dangerous surf are expected Thursday into the weekend. The entire island chain may face serious effects from the storm.

Packing sustained winds of up to 145 mph, Lane is a Category 4 hurricane. It briefly attained Category 5 intensity Tuesday night and early Wednesday before stepping back modestly in strength. The Central Pacific Hurricane Center, based in Honolulu, said it remained a “very impressive hurricane” Wednesday afternoon.

Gradual weakening is expected Thursday and Friday, but “Lane is forecast to remain a dangerous hurricane as it draws closer to the Hawaiian Islands,” the hurricane center said.

The storm may maintain peak winds of 100 mph into Friday, when it is projected to be just south of Maui and Oahu, before weakening to tropical-storm intensity over the weekend.

The hurricane center has posted hurricane warnings for the Big Island and Maui, where tropical-storm-force winds may begin between Wednesday night and Thursday morning. Over the Big Island, rainbands were already beginning to move ashore Wednesday afternoon.

On Wednesday evening, the hurricane warning was extended to cover Oahu, where conditions should deteriorate by Thursday afternoon or night.

A hurricane watch is in effect for Kauai, which the storm is likely to begin affecting Thursday night into Friday. The storm should pull away from the islands by Sunday.

Most computer models do not predict the storm to make a direct hit on the islands. However, a small percentage of them suggest the storm could make landfall in Maui or even Oahu, which would be a worst-case scenario. The general forecast idea is that the storm will run parallel to the entire island chain, potentially sideswiping it with a formidable blow from both water and wind. Exactly how close the storm center tracks to the coastline will determine the severity of its effects.

It’s possible that the center will track close enough for the storm’s core of violent thunderstorms to hammer the islands, especially their south sides, with tremendous rainfall and destructive winds, reaching hurricane force.

In this scenario, 10 to 15 inches of rain would be possible over the island chain, with 20 inches or more possible in the mountains. Especially in this high terrain, such rainfall could lead to devastating flash flooding and mudslides.

“You do not need a landfall for a hurricane to be a deadly — billion dollar disaster,” tweeted Bill Karins, meteorologist for MSNBC. “#HurricaneLane will likely be proof of that because extreme rainfall over mountainous terrain = catastrophic flooding.”

Should hurricane-force winds materialize, they would result in “considerable roof damage to sturdy buildings,” severe damage to mobile homes, “many large trees snapped or uprooted,” “impassable” roads and power outages, the National Weather Service said.

The hurricane center added winds would intensify “over and downslope from higher terrain, and higher in high rise buildings.”

If the storm stays far enough south some or most of the islands would witness more of a glancing blow, with relatively minor effects from the wind.

Regardless of Lane’s exact track, “excessive” rainfall is expected in some areas and the storm is likely to push “large and potentially damaging surf along exposed west, south and east facing shorelines,” according to the hurricane center. The relatively slow motion of the storm will prolong these effects. Towering waves could exceed 20 feet.

The Weather Service is calling for potentially “extreme” effects from this high water, especially for low-lying areas at high tide. “Expect ocean water surging and sweeping over beaches, coastal benches, lava flows, and roadways, creating the potential for significant damage to coastal properties and infrastructure, including roadways,” it said. “Coastal evacuations and road closures are possible. Large breaking waves may affect harbor entrances and channels with significant damage possible to docks, piers, ramps, and boats.”

While tropical storms and hurricanes regularly roam in the waters nearby Hawaii, direct effects from storms as intense as Lane are unusual, and the island chain’s population is not accustomed to them.

Given the multiple hazards posed by the storm and Hawaii’s vulnerability, emergency management and local officials have pleaded with residents to prepare.

“If you’re in the path of #HurricaneLane, get ready now and make sure your family and neighbors do as well,” the Federal Emergency Management Agency tweeted Tuesday.

“Everyone on O‘ahu should take Hurricane #Lane seriously,” tweeted Honolulu Mayor Kirk Caldwell. “Please get your 14-day hurricane kits ready and speak to your family and neighbors to make sure everyone knows what to do.”

In response to the calls to action, residents have been hoarding supplies, with reports of long lines and emptying shelves at grocery stores and other retailers.

The American Red Cross of Hawaii tweeted that it is “seeking volunteers who are willing to be on-call to potentially assist in staffing shelters or assessing damage.”

Gov. David Ige (D), who issued an emergency proclamation for the islands, said he will allow nonessential state employees to go on administrative leave through Friday.

Hawaii’s education department announced all public schools will be closed Thursday and Friday.

To reduce the risk of storm damage, the Navy is moving ships from Pearl Harbor out to sea, Axios reported.

Lane: A historic hurricane in the Central Pacific

As it moved within 300 miles of the islands, Hurricane Lane became the closest Category 5 storm on record to approach Hawaii before it began to weaken. The next closest storm of such strength to approach the islands was John in 1994.

It is only the sixth storm to reach Category 5 intensity in the Central Pacific on record, joining Patsy (1959), Emilia (1994), Gilma (1994), John (1994) and Ioke (2006).

The storm’s central pressure dropped as low as 929 millibars, making it the most intense hurricane (as measured by pressure) since Patricia in 2015 in the eastern half of the North Pacific Ocean.