Chance of heavy rain, thunder to start the work week

A trough moving over the islands from the south will bring the potential for locally heavy rainfall and a slight chance of thunderstorms Monday, with a flood watch posted for all main Hawaiian islands through Monday afternoon.

Winds will be blowing from the south and southeast, bringing showers and possible heavy rainfall to normally dry leeward areas, where downpours can have a higher impact.

The trough will linger west of Kauai through Wednesday, keeping moist and unstable conditions over the islands. The current forecast calls for moisture diminishing over Hawaii Island by late Monday, but lingering near Kauai and Oahu, so the flood watch may be adjusted accordingly.

There’s also a winter weather advisory posted for the summit areas of Mauna Kea and Mauna Loa, with periods of snow and freezing fog overnight.

In surf, wave heights for north and east shores have fallen below advisory levels. A new, long-period west-northwest swell is expected to build Monday night, peaking close to advisory levels. A slightly larger swell is possible Thursday and Friday. Surf on south shores will remain small through the forecast period.

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