Flash flood watch in effect

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Flood advisories were issued Tuesday for the Big Island, with rain expected through the weekend as an unstable air mass passes by the state.

Flood advisories were issued Tuesday for the Big Island, with rain expected through the weekend as an unstable air mass passes by the state.

A flash flood watch also is in effect for Hawaii Island through Thursday afternoon, said National Weather Service forecaster Ian Morrison.

“It looks like it’s going to be wet throughout the week,” he said.

Humid deep tropical moisture moving in from the southeast combined with an upper-level atmospheric trough creates the potential for heavy rainfall and thunderstorms.

The localized rainfall also can lead to flash flooding.

In the first part of the week, rain will occur mainly in the afternoons. Trade winds are expected to resume their normal patterns later in the week, but the moisture and trough instability will remain.

As of 2 p.m. Tuesday afternoon, rain in Hilo was falling at the rate of 2 inches per hour, according to a National Weather Service forecast advisory.

Eastern Maui is expected to receive the brunt of the heavy rainfall. Flash flood warnings were issued for that area, meaning flooding is “imminent or occurring.”

Email Ivy Ashe at iashe@hawaiitribune-herald.com.