HONOLULU (HawaiiNewsNow) – Your HNN First Alert Weather Team has declared Friday as a First Alert Weather Day for all islands except Hawaii island due to the threat of heavy showers that could cause flooding.

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The National Weather Service in Honolulu has also issued a Flood Watch for Oahu, Molokai, Lanai, Maui, and Hawaii Island through 8 a.m. Saturday.

A flash flood warning was up for most of the evening for Oahu which is now under an advisory for until 8:45 p.m.

Radar indicated thunderstorms producing heavy rain over portions of the Koolau mountains, central Oahu, and along the shoreline in leeward Oahu. The heaviest showers were over the higher terrain between Wahiawa and Hauula, and near Nanakuli and Makaha. Rain was falling at a rate of up to 2 inches per hour.

Kamehameha Highway at Waiahole Valley Road was closed, and the highway at Waikane Stream was also closed around 3 pm. Flooding was reported in a residential area near Kunia earlier as well.

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Flash flooding is ongoing or expected to begin shortly. Some locations that will experience flash flooding include Waipio, Wahiawa, Wheeler Field, Mililani, Schofield Barracks, Kunia, Waikele, Pearl City, Waipahu, Waialua, Aiea, Haleiwa, Waikane, Waiahole, Halawa, Makakilo, Punaluu, Hauula, Nanakuli and Waianae.

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Low pressure system to bring flood threat

An unseasonably cold upper level low pressure system will move in over the islands from the north, producing periods of heavy showers that could cause flooding. So far, it has brought 2 to 5 inches on Kauai, which is no longer under a flood watch. The rest of the island chain has received a trace to 2.3 inches of rain.

The weather service says the center of the low is forecast to move over Kauai at around noon and then slowly head northward into the weekend. It is then expected to weaken and slowly drift eastward.

Periods of thunderstorms, heavy showers possible

Unstable conditions within the system can produce periods of thunderstorms and heavy showers that could lead to flooding.

Flood-prone roads and other low-lying areas may be closed due to runoff and overflowing streams from the heavy showers. Urban areas could get more property damage due to rapid runoff.

The flood watch has been extended for Oahu, Maui County and Hawaii Island until 6 a.m. on Saturday.

View the latest weather conditions here.

Download the HNN Weather app from the Apple App Store or Google Play for the latest updates from your First Alert Weather Team: chief meteorologist Jennifer Robbins, meteorologist Drew Davis, and weather anchors Guy Hagi, Ben Gutierrez, and Billy V.

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