Scattered showers, some heavy, are possible as a wet weather system moves over the islands, bringing unstable atmospheric conditions.

An area of what forecasters call “enhanced moisture” is northeast of Maui and moving west.

Strong tradewinds blew some of the wet weather over windward areas this morning and some of those showers could move over leeward sections, forecasters said.

There were reports of short-lived thunderstorms this morning on the Big Island.

Another weather system could also weaken tradewinds as it passes, leading to afternoon rains in leeward and upslope sections.

The forecast for Oahu, Kauai and Maui counties calls for occasional windward and mauka showers overnight and Monday morning. Leeward areas should see partly cloudy skies with scattered showers tonight through Tuesday. Some of the showers could be locally heavy and there’s a slight chance of thunderstorms.

In a special weather statement issued this morning, forecasters warned of the chance of heavy afternoon showers developing because of the unstable atmospheric conditions.

“Motorists may encounter downpours which drastically reduce visibility and cause ponding of water … Don’t drive through any areas where water might cover the road,” forecasters said. “Hikers should be aware that streams may be running high later today and Monday, which could cut off hiking trails. If possible, choose a better hiking day when the weather is quieter.

“Although most spots will not hear thunder today, remember the rule of thumb that if you do hear it, you care close enough to be struck by lightning. When thunder roars, go indoors.”

In addition, a high surf advisory is in effect for south shores of all islands until 6 p.m. Monday. Surf of 6 to 10 feet is expected. The strong breaking waves and strong currents could make swimming dangerous.