Flood Potential Outlook
Issued by NWS Burlington, VT

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Winter/Spring Flood Potential Outlook
National Weather Service Burlington VT
1059 AM EST Thu Feb 16 2017

...Winter/Spring Flood Potential Outlook /4/...

This is the fourth flood outlook for the 2017 winter/spring
season. Flood outlooks are issued bi-weekly by the National
Weather Service in Burlington Vermont to summarize the flood
potential due to snowmelt and break up of river ice across central
and northern Vermont and northern New York.

...Overview...

The flood potential due to snowmelt is near to above normal. The
flood potential due to ice jams is near to above normal.

...Snow Depths and Water Equivalent...

The snowpack has built over the past few weeks and is currently at
its winter maximum across the entire area. Snow depths in the
Adirondacks of northern New York and in the northern Green
Mountains of Vermont into the Northeast Kingdom were 24 to 36
inches over the higher terrain, and 12 to 24 inches in the
valleys. Mountain summits in these areas were covered in six feet
or more of snow. There are 6 to 12 inches of snow in the Saint
Lawrence valley, 8 to 16 inches in the Champlain valley.

Snow water equivalent, or the amount of water held by the
snowpack, was 3 to 6 inches in the valleys of the Adirondacks and
northern Vermont and 5 to 10 inches in the higher terrain mainly
above 2000 feet. Isolated mountain summits had a foot to as much
as 18 inches of liquid in the snow pack. In central Vermont the
snow had a liquid water content of 1 to 3 inches in the valleys
and 3 to 6 inches in the higher terrain. The Champlain and St.
Lawrence valleys had 1 to 3 inches of water in the snow cover.

The snowpack is deep and contains above normal amounts of water.

...River and Soil Conditions...

River flows are generally running near to above normal. Recent
cold temperatures have built ice cover on area rivers. Across
Northern New York state and Northern Vermont, ice thicknesses of 6
to 12 inches are common. Notable ice jams remain in place along
the Missisquoi River at East Berkshire Vermont and the East branch
of the Ausable River near Ausable Forks New York.

Soils are generally frozen, with ground frost sensors showing
frost depths between 6 to 12 inches deep.

Although long term precipitation deficits continue with a
majority of the North Country designated abnormally dry to
moderate drought, precipitation the last couple weeks has been
above normal. Ground water levels have rebounded from late summer
low levels, and USGS monitoring wells show most ground water
levels across the North Country being below normal to near normal.

Lake Champlain is around half foot below normal. Based on the
present snow pack conditions there is a low probability of Lake
Champlain flooding this spring, however it remains a little early
to make an accurate assessment for the lake. It is noteworthy that
the snow pack in the Lake Champlain basin is roughly twice as
much as this time last year. This bodes well for high water levels
from spring melt persisting longer into the summer than was
experienced last year.

...Weather Outlook...

During the first two weeks of February colder temperatures and
stormy conditions became established across the region. The NWS
Climate Prediction Center calls for above normal temperatures and
above normal precipitation through the end of February. The
outlook for the next three months indicated better chances for
above normal temperatures and near normal chances for
precipitation.

...Summary...

The winter/spring flood potential is near to above normal. River
flows are near normal, long term antecedent soil moisture states
are close to normal. The snowpack is now above normal with an
above normal amount of water equivalent. Rivers have had ice form
and thicken over the past couple weeks with colder temperatures
persisting.

It is important to note that heavy rainfall can result in flooding
at any time of the year, even in areas that have little or no snow
on the ground. If the snowpack takes a long time to melt off, this will
leave the area vulnerable to any heavy rainfall events heading
into spring.

The next Winter/Spring Flood Outlook will be issued on Thursday
March 2.

Access current weather conditions and forecasts on our web site
at www.weather.gov/btv.

$$

Neiles


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