Update: Flood watch extended through early Monday morning

Update at 3:40 p.m. Oct. 27: The National Weather Service has extended the flood watch in effect for all main Hawaiian islands until 6 a.m. Monday as flash flooding caused by excessive rainfall continues to be possible.

An upper low remains near the islands and is producing unstable conditions within a very moist atmosphere. This will result in periods of moderate to locally heavy showers statewide through tonight.

Rain that occurs over already saturated grounds could quickly lead to runoff and flash flooding.

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

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

Update at 8:10 p.m. Oct. 26: A flood watch continues for all of the main Hawaiian Islands through Sunday afternoon.

The National Weather Service forecast office in Honolulu reported a low aloft will move over the islands through Sunday, resulting in an unstable atmosphere.

That unstable atmosphere is what led to the heavy rainfall that fell Saturday afternoon over West Hawaiʻi that resulted in a flood advisory that had to be extended.

Flood-prone roads and other low-lying areas might be closed because of elevated runoff and overflowing streams.

Urban areas could also experience more significant flooding and property damage because of rapid runoff.

Update at 4:45 p.m. Oct. 26: The flood advisory for leeward portions of the Big Island has been extended until 7:30 p.m. as minor flooding continues to be expected on roads and in poor drainage areas and streams because of excesive rainfall, including in areas where the annual Ironman triathlon is taking place in Kona.

National Weather Service radar indicated heavy rain at 4:15 p.m. over several areas in West Hawaiʻi, with especially heavy rain from near Waikōloa to Hōnaunau, falling at 1 to 2 inches per hour.

Some locations that will continue to experience flooding include Kailua-Kona, Captain Cook, Waikōloa Village, Hōnaunau, Kealakekua, Kainaliu, Honalo, Kahaluʻu-Keauhou, Hōlualoa, Pōhakuloa Training Area, Kalaoa, Puʻuanahulu, Ocean View, Puakō, Waimea, Miloliʻi, and Waikiʻi.

New areas that will experience flooding include Ellison Onizuka Kona International Airport, Hawaiʻi Volcanoes National Park Kahuku Unit and Waikōloa Beach.

Update at 1:57 p.m. Oct. 26: A flood advisory is in effect until 4:30 p.m. for leeward portions of the Big Island — including areas where the 2024 VinFast Ironman World Championship is taking place — as minor flooding is expected on roads and in poor drainage areas and streams because of excessive rainfall.

National Weather Service radar indicated heavy rain at 1:23 p.m. over several areas on the west side of the island, with rainfall especially heavy over mountain slopes. Rain was falling at a rate of 1 to 2 inches per hour.

Some locations that will experience flooding include Kailua-Kona, Captain Cook, Waikōloa Village, Hōnaunau, Kealakekua, Kainaliu, Honalo, Kahaluʻu-Keauhou, Hōlualoa, Pōhakuloa Training Area, Kalaoa, Puʻuanahulu, Ocean View, Puakō, Waimea, Miloliʻi, and Waikiʻi.

The public is advised to stay away from streams, drainage ditches and low-lying areas prone to flooding.

Original post at 8:40 a.m. Oct. 26: A flood watch is in effect for all of the main Hawaiian Islands through Sunday afternoon.

According to the National Weather Service forecast office in Honolulu, a low aloft will move over the islands today through Sunday, resulting in an unstable atmosphere.

Conditions will be increasingly favorable for the development of heavy showers and thunderstorms, especially over windward areas.

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

A high surf advisory also remains in effect until 6 p.m. today for east-facing shores of a good portion of the state, including those of the Big Island, as a moderate to large, medium period swell continues to slowly decline through the weekend.

Large breaking waves of 7 to 10 feet are forecast this afternoon along eastern shorelines.

Strong breaking waves and strong currents will make swimming dangerous in the advisory areas. The public is advised to heed all advice from ocean safety officials — when in doubt, don`t go out.

The Hawai‘i Department of Transportation reports that both lanes of Bayfront Highway in Hilo are closed through today because of high surf and debris on the roadway.