Lines of showers ahead of an approaching front are already moving across the western and central Hawaiian Islands, with isolated thunderstorms and locally heavy rain possible tonight on Kaua'i and O'ahu, the National Weather Service said.

Strong northeasterly winds will gradually spread over the smaller islands late Sunday and Monday, as this front transforms to a shear line, and moves down the island chain to Maui, forecasters said.

These strong winds, which will eventually veer to a more easterly direction, will be wetter than normal through the first half of next week.

Short-term forecast:

At 4:40 a.m., radar indicated scattered showers were over the ocean just south of O'ahu. These showers are moving northward at about 15 mph and rain will likely spread over various parts of the island, including the Downtown area, Waikiki and Pearl Harbor.

Rainfall amounts of one-quarter inch or more may occur in some areas.

Motorists are urged to use extra caution while driving through the heavier showers due to ponding water on roadways and brief periods of reduced visibility.

The showers are expected to last through 6 a.m. today.

Longer-term forecast:

Today: Scattered showers. The rain could be heavy at times. Widespread haze. Mostly cloudy, with a high near 80. East wind around 8 mph becoming south. Chance of precipitation is 50 percent. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Scattered showers, with thunderstorms also possible after midnight. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 69. East wind between 9 and 11 mph. Chance of precipitation is 50 percent. New rainfall amounts between a quarter and half of an inch possible.

Sunday: Scattered showers. Mostly cloudy, with a high near 80. Breezy, with a east wind between 18 and 20 mph, with gusts as high as 24 mph. Chance of precipitation is 50 percent. New rainfall amounts between a quarter and half of an inch possible.

Sunday night: Showers likely, mainly after midnight. Mostly cloudy, with a low around 68. Breezy, with a east wind around 21 mph, with gusts as high as 26 mph. Chance of precipitation is 60 percent. New rainfall amounts between a tenth and quarter of an inch possible.

Monday: Showers likely, mainly before noon. Mostly cloudy, with a high near 81. Breezy, with a east wind around 21 mph, with gusts as high as 26 mph. Chance of precipitation is 60 percent. New rainfall amounts between a tenth and quarter of an inch possible.

Monday night: Scattered showers. Mostly cloudy, with a low around 69. East wind around 16 mph, with gusts as high as 21 mph. Chance of precipitation is 50 percent. New rainfall amounts between a tenth and quarter of an inch possible.