Update 5:00 a.m.

A tropical storm warning has been issued for Oahu and a watch has been issued for Kauai.

Tropical Storm Darby was 100 miles southeast of Hilo and about 310 miles east-southeast of Honolulu with maximum sustained winds of 50 mph moving west at 9 mph.

Tropical storm force winds extend outward up to 125 miles from the center.

The center of Darby is expected to pass over the Big Island today and Maui tonight, according to the National Weather Service.

Darby is expected to slow slightly today with a turn torward the northwest tonight and Sunday.

Darby is forecast to approach Oahu on Sunday and Kauai on Monday.

Update 2:10 a.m. Saturday

Tropical Storm Darby was 120 miles east-southeast of Hilo and still moving west at 10 mph just before 2 a.m. Saturday.

The storm, which is expected to pass over the Big Island and Maui on Saturday, was 335 miles east-southeast of Honolulu. Maximum sustained winds remained at 60 mph.

Update 11 p.m.

Tropical Storm Darby slowed slightly late Friday night as it continued on a path toward Hawaii island.

Just before 11 p.m., the storm was 150 miles east-southeast of Hilo and 360 miles east-southeast of Honolulu, moving west at 10 mph, down from 12 mph earlier in the day.

Forecasters expect Darby to slow a little more on Saturday before taking a turn to the northwest sometime Saturday night. The center of the storm is expected to pass over the Big Island on Saturday and over Maui on Saturday night.

Maximum sustained winds remained at 60 mph, and tropical storm warnings were still in effect for Hawaii County and Maui County — including the islands of Maui, Molokai, Lanai and Kahoolawe — with a tropical storm warning still in effect for Oahu.

Update 8 p.m.

Tropical Storm Darby was about 180 miles east-southeast of Hilo just before 8 p.m., still moving west at 12 mph with maximum sustained winds of 60 mph.

The storm, which is expected to reach Hawaii island on Saturday, was 390 miles east-southeast of Honolulu.

Tropical storm warnings remain in effect for Hawaii and Maui counties, and a tropical storm warning is in effect for Oahu.

Update 4:55 p.m.

The National Weather Service issued a tropical storm watch for Oahu, in addition to the earlier tropical storm warnings for Hawaii and Maui counties. At 5 p.m., Tropical Storm Darby was about 205 miles east-southeast from Hilo and 415 miles east-southeast of Honolulu, with maximum sustained winds holding steady at 60 mph, and high gusts. It was moving west at 12 mph. Tropical-storm-force winds extend outward up to 125 miles from the center.

“The current forecast has been nudged southward closer … with a landfall on the Big Island, followed by a path over Maui County and near Oahu. The latter part of this path assumes that Darby survives its impact on the Big Island which is not a certainty,” forecasters with the Central Pacific Hurricane Center said.

A warning means that tropical storm winds of 39 mph or more are expected within 36 hours, while a watch means that winds of 39 mph or more are expected in 48 hours.

“Darby’s forward motion is expected to slow slightly Saturday followed by a turn toward the northwest Saturday night. On the forecast track, the center of Darby is forecast to pass over or near the Big Island on Saturday, and Maui on Saturday night,” forecasters said. “The forecast calls for only slow weakening with Darby maintaining tropical storm strength through the weekend. … Interactions with the Big Island may cause significant disruptions to Darby so the intensity forecast confidence is not high at this time.”

Update 3:42 p.m.

Gov. David Ige signed a statewide emergency proclamation today as Tropical Storm Darby bears down on the islands.

The governor’s office said “the proclamation authorizes the expenditure of state monies for quick, easy and efficient relief of disaster-related damages, losses and suffering resulting from the storm.”

“Our top priority is to protect the health, safety and welfare of Hawaii’s residents and visitors. I urge residents and businesses to follow emergency instructions, prepare for the storm and take steps to protect your families, employees and property. The state is standing by to assist the counties — particularly Hawaii and Maui counties— which are expected to be the first to feel the impact of Tropical Storm Darby,” said Gov. Ige.

The disaster emergency relief period begins on July 22 and continues through July 29, 2016.

Update 2:30 p.m.

Tropical storm Darby continued on a westward course that could take it over the Big Island and Maui Saturday.

At 2 p.m., Darby was about 240 miles east-southeast of Hilo and 450 miles east-southeast of Honolulu.

The storm was traveling west at 12 mph and tropical storm force winds extended 125 miles from the center.

Darby is expected to slow slightly and could weaken, but appears to be on course to pass over or near the Big Island Saturday and Maui on Saturday night.

The storm is expected to make a turn to the northwest, but not until Saturday night, after its center passes Hawaii island.

Forecasters said the storm could drop 10 to 15 inches of rain, with locally higher amounts, which could cause life-threatening flash floods and landslides.

Update 1:14 p.m.

Hawaii island Mayor Billy Kenoi has signed an emergency proclamation as Tropical Storm Darby threatens to hit the island today and Saturday.

His office announced today that the proclamation, which is in effect for 60 days, allows easier access to county emergency resources and the suspension of certain laws for emergency purposes.

“We want to make sure we are doing everything possible to protect the public,” Kenoi said in a news release. “This proclamation improves the county’s ability to respond quickly to any potential impacts from the impending storm.”

Update 10:50 a.m.

Tropical Storm Darby is maintaining its strength as it approaches Hawaii island and Maui County.

At 11 a.m., Darby was about 280 miles east-southeast of Hilo and about 490 miles east-southeast of Honolulu with maximum sustained winds of 60 mph. Tropical storm force winds of more than 39 mph extend 125 miles from the center of the storm.

The storm was moving west at 12 mph.

Its current track takes it over or near the northeast coasts of Hawaii island and Maui. But the track could change over the next several hours.

“A direct impact on the Big Island and Maui is a distinct possibility this weekend,” forecasters at the Central Pacific Hurricane Center said.

Forecasters estimate that there is a 63 percent chance of tropical storm winds hitting Hilo. Kahului has a 51 percent chance of seeing damaging winds. There’s a 55 percent chance in Hana; 42 percent in Lanai City and 43 percent in Kaunakakai. Honolulu has a 33 percent chance of winds greater than 39 mph and Lihue has a 23 percent chance.

Previous coverage:

Tropical Storm Darby continued on a course that could take it over or near the Big Island and Maui and the rest of the state this weekend, bringing dangerous surf, damaging winds and heavy rain that could cause “life-threatening flash floods.”

A tropical storm warning posted for Hawaii County is extended to Maui County, meaning tropical storm conditions of winds of more than 39 mph and heavy rains are expected within 36 hours.

A high surf warning is in effect for east shores of Hawaii island and Maui, where surf of 12 to 20 feet, with higher sets is beginning to come ashore. A high surf advisory is in effect for east shores of other islands. Surf on Oahu, Molokai and Kauai could reach heights of 8 to 12 feet through tonight.

At 8 a.m., Darby was 390 miles east of Hilo and about 595 miles east-southeast of Honolulu with sustained winds of 60 mph, moving west at 12 mph.

Based on the lastest forecasts, Darby could bring its strongest winds and rains to the Big Island from late tonight or Saturday until Sunday; on Maui from Saturday until Sunday; Lanai from Saturday until Sunday night; Molokai from Saturday until Sunday night; Oahu from Saturday night until Sunday night; Kauai from Sunday night until Monday.

The National Weather Service posted a flash flood watch for Hawaii and Maui counties starting late tonight through Sunday afternoon. Forecasters said rainfall amounts of 10 to 15 inches are possible over the weekend.

There is still some uncertainty about the exact path of Darby, its intensity and its timing. However, as of this morning, the probabilities that damaging tropical storm conditions will hit Hilo and Kailua-Kona were 51 percent and 36 percent, respectively, according to forecasters at the Central Pacific Hurricane Center. The probabilities for Kahului and Hana were 45 percent and 49 percent, respectively.

Tropical storm-force winds over 39 mph are expected to begin early Saturday. In some areas, winds will be as high as 50 to 60 mph, with gusts to 70 mph.

The strongest gusts will be over mountains, through passes, and where winds blow downslope. Winds affecting the upper floors of high-rise buildings will be significantly stronger than those near ground level.

Homes may see damage to roofs, siding, gutters and windows, especially if these items are not properly secured. Loose outdoor items will become airborne, causing additional damage and possible injury, the weather service said.

Some power lines will be knocked down by falling trees, resulting in scattered power outages. Many large branches of trees will be snapped, and a few trees will be uprooted, forecasters said.

Surf generated by Darby can cause significant wave run up or damage on some windward coastal roads, forecasters said. In Hilo, this includes Bayfront Highway.

The weather service said rains ahead of Darby are already starting to arrive on the windward side of Hawaii island. Heavier rains are expected tonight.

Thunderstorms associated with Darby have rain rates of 2 to 3 inches an hour, forecasters said.

Darby’s heavy rains could result in road closures, damage to roads, and landslides.

Darby is still projected to take a turn to the north, away from the main Hawaiian islands, but the exact timing and the sharpness of that turn is uncertain.

The current path has the turn happening after it gets close to the islands. But if Darby moves north earlier or later or continues straight west, it could significantly change the storm’s impacts.

It’s also unclear how the storm will behave if it makes landfall on the Big Island and Maui. The tall mountains on those islands could cause it to break up.

The last tropical storm to hit the Big Island, Iselle in 2014, was torn apart when it ran against Mauna Kea and Mauna Loa.

Iselle hit the Puna area hard, but the mountains protected the rest of the state from the worst of the storm.

Darby however, could come ashore north of Puna or miss the Big Island.

If it comes ashore on Maui, forecasters said Haleakala would likely weaken it, but it’s not clear by how much.

A path north of Maui would mean the storm will likely maintain its winds and rains, but because the strongest winds and rains are to the north of the center, the impacts may be less depending on how far north Darby passes.

“The heavy rain threat and the high surf threat will persist regardless (of the path of the storm), said Tom Birchard, a meteorologist with the Honolulu office of the National Weather Service.

Forecasters and emergency management officials urge residents in the watch and warning areas to use the relative calm before the storm to prepare by securing loose outdoor items, trimming trees, filling sandbags in areas prone to flooding, and reviewing emergency supplies and plans.

Hawaii County will open emergency shelters on the Big Island today at Hilo High, Waiakea High, Kalanianaole Elementary, Keaau High, Pahoa High, Laupahoehoe Community Charter School, Honokaa High and Intermediate, Kohala High and Elementary, Waikoloa Elementary, Kealakehe High, Konawaena High, Kau High and Mountain View Elementary schools in anticipation of the storm.

In addition, all camping and pavilion reservations are canceled at county parks from today to Sunday.

County swimming pools and the Honolulu Complex will be closed, and the lava viewing area in Kalapana is also closed from today until Sunday.