A National Weather Service graphic illustrates impact of a “major coastal storm,” which threatens heavy rain, high winds and flooding for the region overnight Tuesday to Wednesday.

By John Schwing

WESTPORT — Snow hanging on from the weekend storm should be washed away overnight as heavy rain, driven by high winds, sweeps across the region — triggering river and coastal flooding.

The “Hazardous Weather Outlook” issued for the Westport area by the National Weather Service has multiple warnings for Tuesday night through Wednesday evening:

The impact of what the NWS classifies as a “major coastal storm” could be even more severe because of significant runoff from the melting snowpack. That factor alone could add 0.5 to 1 inches to fresh runoff caused by heavy rain, according to the forecast.

Rainfall across southwestern Connecticut is expected to be at least 2 to 3 inches overnight, with sustained winds of from 25 to 35 mph, gusting as high as 70 mph, the NWS says.

Precipitation, whipped by winds and exacerbated by melting snow, is likely to cause “widespread moderate to major flooding” along small rivers and streams throughout the region, the NWS says. Water levels are expected to remain elevated through Thursday.

Coastal flooding also is expected, particularly during the high-tide period Wednesday morning.

Daytime high temperatures Tuesday are expected to register in the upper-40s, fall overnight to the low-40s and rise to the low-50s Wednesday.

The storm’s intensity should ease by midday Wednesday, and skies will clear overnight, the weather service predicts.

Thursday should be mostly sunny, with temperatures reaching highs in the mid-40s — a weather pattern expected to continue during the day Friday.

However, rain and windy conditions are expected to envelope the area Friday night, continuing into Saturday.

Sunday will be mostly sunny, according to the weather service.

Power disruptions can be reported online at Eversource.com or by calling 800-286-2000. Customers who signed up for the power company’s two-way texting feature can send a text to report an outage and receive outage updates as they happen.

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