UPDATE 4:05 a.m.

There could be a few more scattered showers today, especially over interior and mauka areas this afternoon. But forecasters expect drier weather after heavy rains overnight on Oahu that caused flash flooding and closed the Pali Highway until about 1 a.m.

The forecast for Honolulu and south shores of Oahu today calls for partly sunny skies with scattered showers this morning and isolated showers this afternoon.

Winds will shift to the southeast, bringing humid conditions. Highs will be between 78 and 87 degrees.

Winds will shift again tonight to the northeast under partly cloudy skies with lows between 63 and 72 degrees.

UPDATE 1:25 a.m.

The National Weather Service downgraded the flash flood warning for Oahu to an advisory until 4:15 a.m. today.

Doppler radar at 1:08 a.m. indicated heavy rainfall across southern portions of the Waianae mountains near Makakilo, officials said.

Locations of the advisory include but are not limited to Ewa, Kunia, Kapolei, Ewa Gentry, Makakilo, Ewa Beach and Waikele.

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Heavy rains tonight raised stream levels in Maunawili, trapping 16 hikers, and caused a small rockslide and flooding on the Pali Highway in Kailua.

The rain prompted a flash flood warning for Oahu, in effect until 1 a.m. Thursday, after radar just after 10 p.m. indicated heavy rain over the Koolau mountains in East Oahu, forcing the Punaluu stream above flood stage. The heavy rainfall was nearly stationary, and flash flooding is expected to begin shortly.

Locations in the warning include, but are not limited to, Maunawili, Kahaluu, Hauula, Kaneohe, Waikane, Waiahole and Laie.

A flood advisory for Oahu is also in effect until 12:30 a.m. Thursday for Honolulu, Waimanalo, Kaneohe and Waimanalo Beach.

Flooding forced the second closure of a Kailua-bound lane on the Pali Highway tonight just outside of the tunnel.

Police reported the closure about 9:15 p.m. and said the lane is closed to the first runaway truck ramp.

About 7 p.m., a small rockslide closed one Kailua-bound lane just after the tunnel, but firefighters quickly cleared the rubble, which consisted of about a half-dozen boulders, said Honolulu Fire Department Capt. David Jenkins. The lane was reopened about 30 minutes later.

Rising streams from heavy rainfall also trapped 16 people on Maunawili Trail about 6 p.m. today.

Two adults and three children called for help about 5:30 p.m. when the weather became poor and the streams began to rise, Jenkins said.

They were able to make it back to the trail head, but soon after a second party of four called firefighters for help because they were trapped by rising streams. Firefighters hiked to the party and escorted them out.

About the same time a third party that was highest on the trail called for help because they were trapped by flooding. A fire helicopter reached the group of seven where they were stranded above the waterfall and transported them to a safer area where firefighters hiked to them and escorted them out of the trail, Jenkins said.

None of the 16 people was hurt. Jenkins said firefighters helped the last hikers out by 7:30 p.m.

Forecasters say more rain, thunderstorms and even snow on Mauna Kea and Mauna Loa are possible tonight as unstable and moist air moves over the state.

The National Weather Service said radar at 6:58 p.m. indicated an area of heavy rainfall with rates near 2 inches per hour across already soggy areas of the Koolau Mountains in East Oahu.

A flood advisory for Maui expired at 4:30 p.m. after radar indicated heavy rain with rates of at least an inch an hour over windward Maui.

The advisory included Kahului, Kihei, Lahaina, Pauwela, Waikapu, Kaupo, Haiku, Hana and Makawao.

Forecasters expect a mix of light tradewinds and afternoon sea breezes for the rest of the state today that could bring showers, some locally heavy, to windward slopes and isolated heavy showers to mauka and interior sections in the afternoon.

The unstable weather could also cause thunderstorms to develop and there’s a slight chance of snow on Big Island summits.

The chance of showers remains, but shouldn’t be as heavy on Thursday.

“The weak trade winds will bring some showers to the windward slopes while afternoon sea breezes will generate clouds and a few afternoon showers over the leeward and interior sections,” forecasters said.

The forecast also calls for humid, Kona weather conditions and vog through the holiday weekend.

“Land and sea breezes weather regime will continue over the islands, featuring afternoon clouds and spotty interior showers then partial clearing at night. It may feel rather humid as well. Volcanic emissions from the Big Island may spread to the smaller islands over the weekend under the light southeasterly winds.” forecasters said.

Tradewinds should start to return on Memorial Day, but could remain lighter than normal through next week.