Public Information Statement
Issued by NWS Portland, ME
NOUS41 KGYX 171723
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GRAY ME
125 PM EDT FRI MAR 17 2017
The National Weather Service has declared the week of March
13th through 17th Flood Awareness Week in Maine and New
Hampshire, as well as in the remainder of New England..
...DETERMINING THIS YEAR`S CURRENT CONDITIONS AND FLOOD POTENTIAL...
To help determine the potential for flooding, the National
Weather Service Offices that serve northern New England
continually monitor hydrological conditions throughout the
region. River statements are issued daily and contain
forecasts of the water levels for the major rivers in the area.
Also, during the late winter and early spring the National
Weather Service, in coordination with other federal and state
agencies, power companies, and cooperative observers, surveys
the snow pack across the area to determine the potential for
There are several factors that contribute to the spring flood
potential. These include the amount of snow on the ground, the
amount of water contained in the snow (often referred to as
water equivalent or water content), the density of the
snowpack, and current river and stream levels. The water
equivalent of the snowpack represents the water that will be
released as the snow melts. The density of the snow is an
indication of whether any melted snow (or subsequent rain) can
be absorbed by the snowpack, or will be released. Another
factor is how fast the snow will melt. As a general rule, the
rate of melting is related to the temperature, humidity, and
wind. Warm temperatures accompanied by high humidity and wind
cause the greatest amount of melting. In addition, the state
of the soil (frozen versus thawed and saturated versus
unsaturated) determines whether any melting snow will be
absorbed by the ground. Most importantly, however, the
greatest contributing factor to flood potential is rainfall.
In New England, major flooding does not occur due solely to
In addition, flooding can occur due to ice jams. Ice jams tend
to occur in the spring when water levels on rivers start to
rise and when there is still a significantly thick layer of ice
on the rivers. The rising water in rivers causes the ice to
break up, allowing large chunks of ice to start flowing. These
chunks of ice can jam as they flow downstream. The jammed ice
can then act as a dam and can prevent water and ice from
flowing downstream. Ice jams are unpredictable and water
behind ice jams can rise very quickly. In addition, when an
ice jam breaks up, the resulting release can flood downstream
areas very rapidly.
Please note that the following information on current
conditions is based on snow surveys taken March 6th and 7th.
Please refer to the following web site (in lower case) for the
latest snow conditions in Maine and portions of New Hampshire
The following web site (in lower case) provides up-to-date
river and flood information.
The following web site provides information on ice jams.
.Current snow depth and water equivalent...Snow depths across
western Maine and New Hampshire range from 8 to 20 inches in
southern and coastal areas to 1 to 3 feet in the mountains of
northern New Hampshire and Western Maine with locally higher
amounts. The water equivalent of the snowpack ranges from 2 to
4 inches in the south and along the coast to 6 to 10 inches
with locally higher amounts in the mountains. These values are
near to above normal for this time of year.
.Current snow density...The density of the snowpack generally
ranges from about 20 percent in the mountains to about 30
percent along the coast. A snow pack with a density of at or above
40 percent is considered "ripe" because it will hold no more water
and any rainfall or melting with result in runoff.
.Current river levels...Water levels and flows in rivers and
streams throughout Maine and New Hampshire are generally near
to slightly above normal for this time of year.
.Forecast temperatures and precipitation...
Below normal temperatures are expected to continue for the next
two weeks with near to above normal precipitation. Current
computer model forecasts do not show any major storms affecting
the area during the next week. The continuing cold
temperatures will limit the snow melt during the next two
weeks. Although these lower temperatures reduce the chances
for flooding during the next two weeks, they increase the
chance for flooding later in the season when storms tend to be
warmer and produce more rainfall.
.River ice and ice jam potential... Ice thicknesses are near
normal for this time of year in the mountains. There is
little, if any, ice in southern rivers.
.Flood potential outlook...The overall spring flood potential
across Maine and New Hampshire is near normal in southern areas
and above normal in central and northern Maine and northern New
Flooding is the top storm-related killer in the United States.
Many fatalities occur because people attempt to drive through
flooded roadways. Remember, if you encounter a flooded road,
TURN AROUND, DON?T DROWN!
NATIONAL WEATHER SERVICE