The National Weather Service in Honolulu at 3:07 on Sept. 10, 2018, issued a Flash Flood Watch for all Islands in effect from Tuesday through late Thursday night, Sept. 10 to 12.

Moisture from Tropical Storm Olivia is expected to move over the state starting Tuesday evening. Intense rainfall will be possible, especially along the east-facing slopes.

Olivia is forecast to produce total rainfall amounts of 10 to 15 inches. Isolated maximum amounts of 20 inches may occur along the windward sections of the Big Island and Maui County.

Rain events of this size can cause widespread flooding and can affect areas that do not usually flood. Low spots in roads will become dangerous and impassable due to severe runoff. Debris in streams and gulches may clog bridges and culverts resulting in dangerous flooding. Numerous landslides are expected, especially along the Hana Highway on Maui and the Māmalahoa Highway on the Big Island.

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PRECAUTIONARY/PREPAREDNESS ACTIONS

A Flash Flood Watch means that conditions may develop that lead to flash flooding. Flash flooding is LIFE-THREATENING. Do not cross fast flowing water in your vehicle or on foot.

Monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. If you experience heavy rain or rising water, head to higher ground immediately.