Excessive Rainfall In MA Predicted For Weekend: Weather Service

MASSACHUSETTS — The National Weather Service is predicting a high chance of flooding in Massachusetts this weekend with heavy rain set to continue to hammer New England through Sunday.

The weather service is predicting at least a 40 percent chance of excessive rainfall leading to flash flooding on Friday and on Sunday. New England is the only part of the country with such a high chance of flash flooding this weekend.

"At this point the two wettest periods look to be Sunday and to a lesser extent Tuesday, with lulls in rain and thunderstorms in between. Sunday is looking increasingly concerning with regards to flash flooding which is why the [Weather Prediction Center] has placed much of the region within a Moderate Risk (level 2 of 3) of excessive rainfall," the National Weather Service in Norton said in a weekend outlook.

In Massachusetts, the high chance of excessive rainfall on Friday extends from the Berkshires to Worcester, with more eastern parts of the state likely to see less rain. Saturday will be relatively dry, although there's still a 50 percent chance of rain in the forecast.

A flood warning was issued Friday morning for Worcester County and parts of northern Middlesex and Essex counties due to heavy rains. That warning, which means flooding is imminent, expires at 3:45 p.m.

Heavy rain returns Sunday with the chance of flooding at 40 percent chance or greater across a wider section of the state extending into Middlesex and Norfolk counties, according to the forecast.

Forecasters are paying close attention to the precipitable water values (PWAT) — the measure of water vapor in the air if it were to be condensed — possible on Sunday. The weather service in Norton reported the PWAT values are predicted to be near 2-1/2 inches, which is less than a quarter inch below the record for the state measured above Chatham.

New England has seen multiple storms this week that have dropped devastating rains, causing damaging floods in Vermont and the Connecticut River Valley. The weekend storms may forestall cleanup efforts, especially in the Pioneer Valley.

"Sunday actually looks more impressive with the PWATs off the charts. Moderate risk means widespread heavy rain possible with numerous flash floods likely. Very difficult to predict who gets hit and how much. But expect showers/storms with torrential rain," the New England forecasting service eweather reported Friday morning.

Some parts of Massachusetts — especially central parts of the state — could end the weekend with an additional 3 to 4 inches of rainfall, the NWS Northeast River Forecast Center said Friday morning.