Update: Waipiʻo Valley Road to be closed

Update at 5:45 p.m. Jan. 29: Hawai‘i County Civil Defense says Hawai‘i Police Department reports Waipiʻo Valley Road in Hāmākua on the east side of the Big Island will be closed at 6 a.m. Thursday (Jan. 30) because of the flood watch in effect for the island. 

Waipiʻo Valley residents and farmers are authorized to access the valley.

The public will be informed as conditions change.

Update at 3:01 p.m. Jan. 29: National Weather Service forecasters in Honolulu have changed the parameters for the high wind watch that goes into effect for lower elevations of much of the state, including the Big Island, as a significant winter storm approaches from the northwest.

The high wind watch will now be in effect from 6 a.m. Thursday (Jan. 30) through 6 a.m. Friday (Jan. 31). It was previously issued for 6 p.m. today (Jan. 29) through 4 a.m. Friday.

Southwest winds of 20 to 40 mph, with localized gusts of more than 60 mph, are possible during the watch period.

A flood watch also goes into effect later tonight for the island, except the summits of Mauna Kea and Mauna Loa, which will be under a winter storm watch. They were put under a high wind warning at noon today.

Update at 8:11 a.m. Jan. 29: The National Weather Service forecast office in Honolulu has already extended a flood watch in effect for the entire state, including all of the Big Island except the summits of Mauna Kea and Mauna Loa, as a major winter storm draws closer to the islands.

It also upped the ante for high winds associated with the storm atop the tallest summits on the Big Island.

The flood watch was originally set to run from 6 p.m. today (Jan. 29) through noon Friday (Jan. 31); however, it will now be in effect all day Friday, through 6 p.m.

Meanwhile, a high wind warning also will be in effect from noon today through 6 a.m. Friday for the summit areas of Mauna Kea and Mauna Loa.

That’s a step up from the previous high wind watch issued for the summits and a longer time period.

Southwest winds of 40 to 50 mph with gusts up to 90 mph are expected atop the mountains, which could lead to property damage, including roof damage; power outages; and downed trees and power lines.

Forecasters also warn that winds that strong will create hazardous driving conditions as powerful cross winds will pose a serious risk for drivers, especially for lightweight and high-profile vehicles.

Loose outdoor items should be brought inside or secured properly.

A high wind watch will also be in effect from 6 p.m. today through 4 a.m. Friday for lower elevations of all islands as southwest winds associated with the storm are forecast at 20 to 35 mph, with gusts up to 55 mph possible.

And the summits of Mauna Kea and Mauna Loa as well as Haleakalā on Maui will be under a winter weather watch from midnight Thursday (Jan. 30) until noon Friday.

Forecasters in Honolulu expect cool and pleasant conditions to linger this morning before quickly transitioning through the day as winds shift out of the south-southeast ahead of the strengthening winter storm approaching from the northwest.

The low pressure system will pass just north of Kaua‘i on Thursday, with a cold front advancing down the island chain Thursday through Friday.

Guidance remains in good agreement and depicts an active weather pattern unfolding beginning late tonight through early Friday, with forecast models continuing to support a potential significant event evolving across the state.

Impacts will range from flash flooding and strong to severe thunderstorms to damaging south to southwest winds, which will downslope into north through windward sections of the state.

Additionally, deep convection will support the potential for periods of heavy snow late Thursday through Friday atop Mauna Kea and Mauna Loa.

The area forecast discussion for the state from early this morning says conditions will fortunately improve quickly behind the front Friday night into the weekend, continuing through early next week.

Original post from 1 a.m. Jan. 29: National Weather Service forecasters in Honolulu have issued several watches in advance of a major winter storm expected to strike the state later this week.

A flash flood watch will be in effect from 6 p.m. Jan. 29 until noon Jan. 31 for all Hawaiian islands, including the Big Island, because of the threat of flash flooding caused by excessive rainfall from the coming storm.

A strong winter low pressure system will develop Wednesday west of the state and pass by Thursday just north of Kaua‘i, with an associated cold front moving eastward across the state Thursday into Friday.

Conditions will become increasingly favorable for the development of heavy showers and possibly thunderstorms over the western end of the state starting Wednesday evening, then progressing east on Thursday and continuing through Friday morning.

Flood-prone roads and other low-lying areas could be closed because of elevated runoff and overflowing streams. Urban areas also might see more significant flooding and property damage because of rapid runoff.

The public should monitor later forecasts and be prepared to take action if flash flood warnings are issued.

A high wind watch will be in effect from 6 p.m. Jan. 29 through 4 a.m. Jan. 31 for lower elevations of all islands, as southwest winds associated with the storm are forecast at 20 to 35 mph, with gusts up to 55 mph possible.

Strongest winds will likely be across windward and mauka (toward the mountain) areas of O’ahu and Kaua’i. However, portions of Maui County and the Big Island could also see periods of strong winds.

Damaging winds could blow down trees and power lines, and widespread power outages are possible. Travel also could be difficult, especially for high-profile vehicles.

The public is advised to take precautions now to protect property, including tying down or moving loose objects to a sheltered location.

Big Island summits of Mauna Kea and Mauna Loa and the summit of Haleakalā on Maui also will be under a high wind watch during the same time period, as southwest winds of 40 to 50 mph are expected, with gusts up to 80 mph possible.

Winds this strong can make driving and even walking dangerous. They can even forcefully open doors and damage hinges or slam doors shut, possibly causing injuries.

All three summits will be under a winter weather watch from midnight Jan. 30 to noon Jan. 31.

Periods of snow and mixed precipitation are in the forecast atop the mountains, with snow accumulations up to 4 to 8 inches possible. A light glaze of ice is also possible on wet surfaces as temperatures drop below freezing.

Travel could be very difficult to impossible. Blowing snow will significantly reduce visibility at times, with periods of zero visibility.

Anyone planning travel to the summits, including hikers and campers, should monitor the latest forecasts and consider postponing their trip until weather improves.