Public Information Statement
Issued by NWS Portland, ME

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000 NOUS41 KGYX 161403 PNSGYX Public Information Statement National Weather Service Gray ME 1000 am EST Fri Mar 16 2018 The National Weather Service has declared the week of March 12th through 16th 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 spring flooding. 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 typically occur due solely to melting snow. 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 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 provides up-to-date river and flood information. The following web site provides information on ice jams. CURRENT CONDITIONS: .Current snow depth and water equivalent...Snow depths across New Hampshire range from about 1 to 3 feet with locally higher amounts in the mountains. The water equivalent generally ranges from 2 to 5 inches across lower elevations with up to 10 inches along the Canadian border and in the mountains. These values are generally near normal for this time of year except in northern New Hampshire where they are above normal. In western Maine snow depths range from 1 to 3 feet in coastal and interior zones with 2 to 4 feet in the foothills and mountains with locally higher amounts. The water equivalent of the snowpack in western Maine ranges from 2 to 5 inches in coastal and interior zones to 5 to 10 inches in the foothills and mountains. These values are generally above normal for this time of year. .Current snow density...The density of the snowpack generally ranges from about 20 to 30 percent across the region. 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 western Maine and New Hampshire are generally above normal for this time of year. .Forecast temperatures and precipitation... Below normal temperatures are expected for the next two weeks with near normal precipitation. Below normal temperatures at this time of year delay the snowmelt and increase the chances for flooding later in the season due to the possibility of a rapid warm-up in temperatures. In addition, the current computer model forecasts show a continuation of East Coast storms that could possibly increase the snowpack and water equivalent across the region. .River ice and ice jam potential... Although ice remains on a few headwater rivers and streams, most rivers are now open and free of ice. .Flood potential outlook...The overall spring flood potential across Maine and New Hampshire is above normal across New Hampshire and western Maine. 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! $$ JENSENIUS/HAWLEY NATIONAL WEATHER SERVICE GRAY, MAINE NNNN is the U.S. government's official web portal to all federal, state and local government web resources and services.