Snowmelt Flood Risk: Worcester, Boston, Hartford

By Anthony Sagliani, Meteorologist
March 12, 2013; 8:54 PM ET
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Play video A look at the forecast for the Northeast.

A band of slow-moving, drenching rain will cross eastern New England into Tuesday night, bringing a risk of flooding to Connecticut, Massachusetts, Rhode Island, New Hampshire and Vermont.

The combination of rain and recent melting snow contributed to minor flooding problems in parts of Virginia and western Maryland Tuesday. Flooding problems are possible farther north Tuesday night in New England.

Some neighborhoods around Boston, Worcester, Brockton, Foxboro, Fitchburg, Lowell, Taunton, Hartford, Danielson, Nashua and other towns and cities could experience street flooding.

With 10 to as much as 20 inches of snow on the ground in many areas, the danger of flooding will come not only from the rain itself, but also snowmelt.

Recent analysis from a NOAA satellite indicated that, if melted, the snowpack held the equivalent of 1.00-2.00 inches of rain from western and central Massachusetts into southern New Hampshire.

Here is an example of how snowpack acts to store water, and then unleash it as additional runoff.

Steady drenching rain expected will bring up to another inch of rain on top of this, and the result will be rather widespread urban and poor drainage flooding in the I-95 corridor from Providence, R.I. to Portsmouth, N.H.

This will have a large impact on the evening commute as heavy traffic delays are likely.

Additionally, excessive runoff from the rain and melting snow will lead to large standing pools of water in fields and around homes, ranging anywhere from a few inches to a few feet deep in spots.

Areas that don't normally have flooding could briefly be flooded in this type of situation.

There is also potential that some rivers, creeks and streams will go into flood stage during the afternoon and evening hours on Tuesday, especially in the most flood-prone areas. Any flooding of rivers, creeks and streams will be minor, however.

Farther to the north, in central and northern New England, the snowmelt and rainfall will also combine with river ice to bring the potential of flooding. Interests along the banks of streams and rivers should be prepared to take quick action for ice jam related issues.

Large chunks of melting ice in rivers can easily become stuck on debris, or lodged around bends on rivers and streams. As the flow of the water carries more large chunks into the same spots, a natural, temporary dam can develop. The water will eventually back up behind the dam, and severe flooding can occur. This is known as ice jam flooding.

This natural dam can also break easily and quickly, and when it does, water backed up behind the jam will rush down the river or stream, flooding locations that were initially safe.

To be prepared, and if you can safely do so, remove any snow or ice from drainage areas near your home. If you will be traveling on Tuesday and Tuesday evening, be sure to allow plenty of time to reach your destination. Remember: Never drive around barricades or flooded roadways, as the water may be much deeper than you think.

The rain will come to an end Tuesday night, and much colder air will be ushered into the region for Wednesday and much of the remainder of the week.

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