Flood Potential Outlook
Issued by NWS Portland, ME

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Winter/Spring Flood Potential Outlook
National Weather Service Gray ME
241 PM EDT Thu Apr 27 2017

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK...

The flood potential is about normal for the time of year.

This is the ninth and final in a series of regularly scheduled
flood potential outlooks that are issued during the winter and
spring seasons. These outlooks will be issued every two weeks
until the end of the snow melt season, and will assess the
potential for flooding based on a number of factors.

...CLIMATOLOGICAL GUIDANCE...

An active weather pattern is expected into the second week of May
with several chances for rain.

The official National Weather Service 6 to 10 day and 8 to 14 day
forecast calls for above normal precipitation and normal to below
normal temperatures.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENT...

...NEW HAMPSHIRE...

Snow is now confined to the high peaks of the White Mountains and
far northern Coos county near the Canadian border.

At Moose Falls near the Canadian border a snow depth of 21 inches
was measured on April 24 with a water equivalent of 9.0 inches. At
Second Connecticut lake snow depth was 13 inches with a water
equivalent of 5.5 inches.

...WESTERN MAINE...

In Maine snow is confined mostly to areas near the Canadian
border where 2 to 4 inches of water equivalent still exists. In
Bald Mountain Township north of Jackman a survey crew measured 4.2
inches of snow water equivalent in 10 inches of snow on Tuesday
afternoon.

...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...

Soil moisture anomaly maps indicate normal soil moisture across
western Maine and all of New Hampshire.

The long term term Palmer Drought Severity Index shows normal
conditions across Maine and New Hampshire.

Reservoirs in the Kennebec River basin are above normal for the
time of year.

Reservoirs in the Androscoggin River basin are 82 percent full
which is 25 percent above normal.

At the end of March First Connecticut Lake in northern New
Hampshire was 215 percent of normal and 57 percent full. Lake
Francis was 180 percent of normal and 67 percent full. Lake
Winnipesaukee was 82 percent of normal and 81 percent full.

In New Hampshire groundwater levels courtesy of the USGS show a
mix of above and below normal groundwater. Those wells that are
below normal are rising as the recent rain and melting snow have
started the recharge.

In Maine monitoring wells are normal or above normal.

...RIVER AND ICE CONDITIONS...

River flows are above normal for the time of year in both western
Maine and New Hampshire.

...IN CONCLUSION...

Based on the above information the flood potential is about normal
for the time of year across western Maine New Hampshire. The
snowpack melted in a controlled fashion this spring resulting in
just minor flooding. There is still snow in the mountains but the
areal extent of the remaining snowpack is small enough to not
cause any further concerns. We will remain in an active weather
pattern with precipitation expected every few days, however in the
absence of a widespread heavy rain it appears as though we will
get through the remainder of the spring without a major flood.
Rivers will remain high for the next 1 to 2 weeks, but once the
foliage greens-up rivers should recede fairly quickly.

It is important to note that major flooding does not occur from
snowmelt alone. Rainfall, how much and in how short a period of
time is the most important factor in determining the severity of
flooding.

Another Winter/Spring Flood Potential Outlook will be issued in
January 2018.

$$

TFH



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