PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GRAY ME
700 AM EST WED MAR 20 2013

The National Weather Service has declared the week of March 
18th through 22nd Flood Awareness Week in Maine and New 
Hampshire, as well as the remainder of the United States. 

...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 is based on snow 
surveys taken March 11th and 12th.  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/mema/weather/snow.htm

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 (AS OF March 15):

.Current snow depth and water equivalent...Snow depths 
across western Maine and New Hampshire range from 6 to 18 
inches in southern and coastal areas to 18 to 30 inches in 
northern New Hampshire and the Western Mountains of Maine.  
The water equivalent of the snowpack ranges from 2 to 5 
inches in the south and along the coast to 6 to 9 inches in 
the mountains.  These values are about normal for this time 
of year.

.Current snow density...The density of the snowpack general 
ranges from about .30 in the mountains to about .40 along 
the coast.  A snow pack with a density of at or above .35 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 on the higher 
end of the normal range for this time of year.  

.Forecast temperatures and precipitation...No major storms 
are expected in the next week and rivers are expected to 
remain at near normal levels.  Temperatures over the next 
week are forecast to be near to slightly below normal.  
Precipitation is forecast to be near to slightly above 
normal.
 
.River ice and ice jam potential...The warm winter 
temperatures have cleared many rivers of ice across southern 
and coastal areas of Western Maine and New Hampshire.  On 
other rivers and streams where ice remains intact, ice 
thicknesses are below normal.

.Flood potential outlook...The overall spring flood 
potential across Maine and New Hampshire remains is in the 
normal range.  The snow pack is generally normal, rivers and 
stream levels are near normal, and the ground is saturated.  

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

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