The National Weather Service issued a flash flood watch for most parts of Oahu set to take effect this evening through late Tuesday night and warned of heavy snow on Hawaii island summits tonight.

A slow-moving cold front is expected to move down the island chain tonight through Wednesday, bringing abundant moisture ahead of it that may develop into heavy showers and thunderstorms, forecasters say.

The flash flood watch is in effect for Oahu’s south shore, Waianae coast, North Shore, Koolaus, Olomana and Waianae mountains.

A winter weather warning is also set to go into effect from 6 p.m. today until 6 a.m. Thursday, with heavy snow expected at Mauna Kea and Mauna Loa summits.

Total snowfall of between 1 to 2 feet, with higher localized amounts, is expected above the 12,000-foot elevation level on the Hawaii island summits. Strengthening winds could lead to blizzard conditions, weather officials said.

Expect heavy snow accompanied by strong, gusty winds at times, reducing visibility. Travel to the summits will be extremely hazardous or impossible.