Public Information Statement
Issued by NWS Portland, ME

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992 NOUS41 KGYX 171723 PNSGYX 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 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 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 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 http://www.maine.gov/rfac/rfac_snow.shtml The following web site (in lower case) provides up-to-date river and flood information. http://weather.gov/nerfc The following web site provides information on ice jams. http://icejams.crrel.usace.army.mil/ CURRENT CONDITIONS: .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 Hampshire. 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

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