Expect a mixture of sun and clouds this morning on Oahu with the chance of heavy showers looming over all islands.

A flash flood watch continues for the state as unstable weather conditions are predicted to continue through Friday morning.

Thunderstorms overnight generated heavy rain on Oahu, a waterspout south of Honolulu Airport and snow on the Big Island.

Lighting and loud thunder could be seen and heard last night and throughout the early morning on Oahu. The island was under a flash flood warning for several hours until 2:15 a.m.

Gauges at Pacific Palisades showed rain falling at a rate of an inch an hour at about 11:30 p.m., the city’s Department of Emergency Management said. Police said ponding was reported on Moanalua Road near Grace’s Drive-In and on Waialua Beach Road.

Nearly 4 inches of rain fell in Waiawa during the 24-hour period ending at 5 a.m. Pacific Palisades got 3.8 inches; Mililani had 3 inches; and Manoa recorded 2.7 inches.

Jonathan Hoag, a National Weather Service forecaster, said more rain will likely fall this afternoon and evening on Oahu.

"The overall situation is still quite unstable," he said.

Don’t be deceived by sunny skies this morning, he said. With all the moisture in the air, warm weather increases the chance of heavy rain later in the day and evening as the heat rises and forms rain clouds.

"Where it is presently sunny, it will soon become cloudy," he said. "That kind of occurred yesterday. A little bit of heating started convective shower growth over the ocean and land," Hoag said.

The Honolulu Airport tower reported seeing a waterspout about 20 miles south of Oahu at about 6:35 p.m., Hoag said. About 4 to 6 inches of snow also fell on Mauna Kea and Mauna Loa yesterday. The mountain summits remain under a winter storm watch and the road to the summit was closed.

The "spotty and localized" thunderstorms and heavy showers are circulating around a low pressure system south of Kauai created by a weakened cold front from the northwest meeting warm, moist air from the southeast, Hoag said.

Radar showed heavy rain southeast of the Big Island this morning that could move onshore. Kauai and Windward Oahu could also get rain.

Hoag said conditions should gradually clear as the low pressure system moves off to the west Friday and Saturday. But the atmosphere will still be moist and conditions may be humid, with the chance of showers through the weekend.