Long Island Weather: Flash Flood Watch Canceled For Nassau

UPDATE 5 p.m.: From the NWS: Canceled the flash flood watch for all but Suffolk County, and even there the chances for very heavy rain capable of flash flooding are diminishing. The heaviest rain per latest radar was over southern N.J., Delaware, and the nearby coastal waters, and heading northeast.

The National Weather Service has issued a flash flood watch for Long Island with multiple rounds of heavy rain expected to soak the region Monday. The watch is in effect from noon Monday until 6 a.m. Tuesday.

Rain will overspread the island by the early afternoon. Rainfall totals of 1-2 inches with locally higher amounts are expected across the watch area, especially in any thunderstorms, the NWS said.

The odds of thunderstorms, mainly Monday night, have decreased from earlier forecasts, but any that do develop have the potential to be severe.

"With the warm front across the area and strong directional and speed shear, the coastal areas of NYC and Long Island will need to be monitored closely as the warm ocean waters may locally support cells capable of rotation and perhaps a brief waterspout/tornado," the NWS said in a forecast discussion Monday morning.

The full forecast:

Monday- Showers, mainly after 10am. High near 73. Light east wind becoming southeast 10 to 15 mph in the afternoon. Chance of precipitation is 90%. New precipitation amounts between a half and three quarters of an inch possible.

Monday Night- Showers and possibly a thunderstorm before 2am, then showers likely. Some of the storms could produce gusty winds and heavy rain. Low around 66. Southeast wind 9 to 15 mph becoming northwest after midnight. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Tuesday- Partly sunny, with a high near 80. Northwest wind around 11 mph.

Tuesday Night- Partly cloudy, with a low around 65. Northwest wind 6 to 9 mph.

Wednesday- Sunny, with a high near 79. North wind around 6 mph becoming south in the afternoon.

Wednesday Night- Mostly clear, with a low around 67.