An upper low will trigger heavy rainfall across portions of the main Hawaiian Islands through the weekend. Trade winds will focus showers over windward and mauka areas, with heavy showers and thunderstorms possible leeward mainly during the afternoon and evening hours.
Instability associated with the upper low will increase heavy rainfall and thunderstorm potential over the next couple of days. The greatest threat will remain over Kauai, but locally heavy showers and isolated thunderstorms will remain possible across Maui County and the Big Island as well. A Flash Flood Watch remains in effect until 6 p.m. Sunday for Niihau and Kauai, where the flash flood threat is the greatest.
A brief return to a trade wind pattern is expected early this week, followed by a land and sea breeze pattern Wednesday and Thursday. Another switch to trade wind weather is then possible by the end of the week.
A High Surf Advisory for east facing shores has been exended through 6 p.m. Sunday. No other significant swells are expected, with a small WNW swell expected Tuesday through Thursday, and small S to SE swells through the period.