Although scattered showers are possible, they should begin to lessen on Halloween night. But National Weather Service forecasters expect more rain this afternoon, and on Sunday and Monday on Oahu.

This morning the National Weather Service issued a short term forecast because of the chance of thunderstorms and heavy rain moving over Oahu. 

Forecasters said a line of heavy showers moved over southeast Oahu from Hawaii Kai to Diamond Head at 9:20 a.m. and the rain was headed west with rates of 1 to 2 inches per hour.

A weather system west of the islands is cutting off the cooling tradewinds this weekend and instability in the atmosphere and daytime heating is creating a chance of heavy rain, perhaps thunderstorms today.

“Clouds and showers will generally favor mauka areas each afternoon and evening, then decrease overnight,” forecasters said. “Kauai and possibly Oahu are forecast to be rather wet Sunday and Monday, while the rest of the island chain will continue to experience a somewhat dry land and sea breeze pattern. The entire state will be under humid southeast to south low level flow.”

The southerly winds are bringing increased humidity until tradewinds return, likely on Tuesday.

Heavy rains overnight prompted a flood advisory for East and Windward Oahu, which expired this morning.

In the 24-hour period ending at 8 a.m., about 2.7 inches of rain fell at the Lyon Aboretum in Manoa; 2.1 inches was recorded in upper Nuuanu and more than 2.5 inches fell in the Oahu National Wildlife Reserve in the northern Koolau mountains.

The forecast for Waikiki and south shores of Oahu calls for a 20 percent chance of rain tonight, with cloudy skies, isolated showers and hazy conditions.