Heavy rain, snow and perhaps hail might fall over the islands as warm moist air from the southeast is predicted to collide with cold air from the northwest over the islands tomorrow.

National Weather Service forecasters say unstable weather and possibility of heavy rain will likely be with us through the weekend, clearing on Monday or Tuesday.

A flash flood watch will be in effect for all islands from late tomorrow through Thursday, the weather service said.

Skies will become cloudier today through tonight with scattered showers

Tomorrow should begin with some sun. But thundershowers could move in by the afternoon or evening. Forecasters say there’s a 50 percent chance of showers and thurderstorms for Honolulu on Wednesday

The storm system is similar to rains in February and could bring snow to Big Island summits.

“It is more like a winter storm system,” forecaster Chris Brenchley said. “It’s a little bit out of season.”