The National Weather Service has ramped up its weather alerts today as a large north-northeast swell approaches the islands.

While many residents remain under a flood watch today, the focus is shifting toward the shoreline, where surf heights are expected to reach dangerous levels.

A new high surf warning will take effect at noon today for the north and east shores of Niihau, Kauai, Oahu, Molokai, Maui and Hawaii island. This warning is scheduled to remain in place through Tuesday afternoon. Forecasters expect waves along north shores to build to 10 to 16 feet today before peaking at 20 to 25 feet late tonight and Tuesday. East shores should see surf of 7 to 10 feet this afternoon, building to 12 to 16 feet tonight and Tuesday.

The impact for these coastal areas is expected to be “very high” with weather officials warning that “ocean water surging and sweeping across beaches” could create “the potential for impacts to coastal roads and infrastructure.” Swimmers and boaters should also be aware that “powerful longshore and rip currents will be present at most beaches.”

Starting at 6 p.m., a high surf advisory will also go into effect for several other coastlines. West shores of Hawaii island in the Kohala districts will see surf building to 6 to 10 feet. On Maui, west shores will see waves between 8 and 15 feet. The west shores of Molokai and the north shores of Lanai are expected to see the biggest surf at 10 to 16 feet.

Inland conditions remain unsettled as the flood watch remains in effect through this afternoon for most of the state except Hawaii island. This is a continuation of the watch issued on Sunday. Because the ground is already saturated from previous heavy rain, there is a lingering risk of flash flooding, forecasters said.

Runoff from additional showers could cause problems quickly. The weather service notes that “flood-prone roads and other low-lying areas may be closed due to elevated runoff and overflowing streams.” They also caution that “urban areas may receive more significant flooding and property damage due to rapid runoff.”

On Hawaii island, conditions at the summits are changing. A previously issued high wind warning for Mauna Kea and Mauna Loa has been canceled and replaced with a wind advisory in effect until noon today. Sustained winds are blowing between 40 and 50 mph with gusts reaching 60 mph today.

The summit conditions present physical risks for anyone in the area. The weather service said that “winds this strong can make driving and walking dangerous” and noted that “the winds can forcefully open doors and damage hinges or slam doors shut, possibly causing injuries.”

A cooling trend is expected to follow this unstable weather. As a drier air mass moves in tonight, temperatures will drop into the 50s and 60s for many areas. This pattern of breezy tradewinds and cooler nights is expected to persist through Thursday.

The weather on Tuesday will be mostly cloudy and breezy with northeast winds between 15 and 25 mph, according to the NWS. Windward and mauka areas can expect scattered showers during the day, followed by isolated showers at night. Highs should stay between 73 and 78 degrees.

Conditions on Wednesday are expected remain mostly cloudy with isolated showers for windward and mauka areas. Highs will again range from 73 to 78 degrees while lows drop to between 62 and 67. Tradewinds will continue at 15 to 20 mph.

On Thursday the islands are forecast stay mostly cloudy with isolated windward showers. Highs will climb slightly to between 75 and 80 degrees. Trades will hold steady at around 15 mph as the drier air mass remains in place.

On Friday cloudy skies are forecast for windward areas with isolated showers continuing. Winds will begin to shift from the east as a new front starts to approach the state from the west. Highs will reach between 76 and 81 degrees.