Long Island weather: Heavy rain, possible flooding for Monday

Most of Long Island will see more than an inch of rain Monday to start the post-Thanksgiving workweek, including possibly heavy rain that could snarl the evening commute and coastal flooding.

Temperatures will fall Sunday night to about 40 degrees on most of the Island, with some stray showers possible early Monday morning, said Faye Morrone, a meteorologist for the National Weather Service in Upton.

“It looks like the rain doesn’t arrive in earnest until 10 a.m. or so, and then it continues through the afternoon and evening before it begins tapering off tomorrow night,” she said.

The weather service issued a coastal flood warning for 8 to 11 a.m. Monday for south Nassau County, which means two to three feet of flooding is expected in vulnerable low-lying areas.

For northern Nassau County and northwest Suffolk County, there is a coastal flood advisory from noon to 3 p.m., with one to two feet of flooding expected in vulnerable areas. In northeast and southeast Suffolk, brief, minor flooding of low-lying areas is forecast in the late morning and early afternoon Monday. For southwest Suffolk, the advisory is in effect from 9 a.m. to 1 p.m. Monday.

There also is a small craft advisory on Long Island Sound on Monday, with winds of 15 to 20 knots expected and gusts of up to 35 knots.

Highs Monday are expected to be in the low 50s, with a low around 40, with breezy conditions much of the day, Morrone said. The average high for Monday in Islip is 50; the average low is 34.

Tuesday will be chillier, with highs in the mid- to upper 40s and lows around 30. Skies should be cloudy in the morning, with the sun breaking through in the afternoon.

Wednesday is expected to be even colder, with a high of 40 and lows in the lower 30s, with a small chance of a shower during the day.

On Thursday, highs are forecast in the mid-40s with lows in the mid-30s, although temperatures in the pine barrens could drop to the mid-20s. Sunny skies are expected.

On Friday, highs are expected to be in the low 40s, with lows in the low to mid-30s.

Looking toward next weekend, expect a dry Saturday with highs in the mid-40s.  Rain is possible Saturday night into Sunday and  the high temperature Sunday around 50 is likely.