HONOLULU (KHON2) - Chances of heavy rainfall and thunderstorms should diminish greatly by morning as the sharp upper-level trough passes east of the islands, with the highest rainfall chances lingering around Maui County and the Big Island into Monday afternoon. Breezy and gusty northerly winds will develop behind the front tonight, and the cool northerly will persist from at least Molokai westward on Monday, with variable winds favored on the Big Island. Tuesday through early Wednesday will be a transition period. The northerly winds will ease and eventually shift out of the east as weak surface high pressure to the north briefly exerts some dominance. Some moisture could remain hung up on windward slopes of the Big Island and Maui, with minimal shower activity expected elsewhere. A potent winter low will affect the state Wednesday night through Thursday night, bringing a significant threat of strong to potentially damaging southwest winds, flooding, and strong thunderstorms. A winter system of this strength at such a low latitude is quite rare in the Central Pacific, and while it is still too early to pin down details, probabilities for significant impacts are rising. Southerly winds will ramp up Wednesday night, and as winds veer out of southwest on Thursday, damaging downslope wind gusts could occur near and northeast of terrain, especially across the western half of the island chain, and winds on the high summits of the Big Island and Maui will be very strong. Bands of heavy rainfall could develop as early as Wednesday night and will bring a threat of flash flooding, especially Thursday and Thursday night. Ensemble guidance suggests that the highest rainfall totals will be over the northern end of the island chain, but the flood risk still cannot be ruled out statewide. Thunderstorms developing within the gusty southwest flow could also produce isolated areas of wind damage over any location, but confidence in this threat remains lower. Also, expect winter weather on the high summits of the Big Island.