Flood Potential Outlook
Issued by NWS Burlington, VT

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Winter/Spring Flood Potential Outlook
National Weather Service Burlington VT
919 PM EST Thu Jan 19 2017

...Winter/Spring Flood Potential Outlook /2/...

This is the second 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 below normal for
northern New York and western Vermont including the Champlain
Valley, and near normal for central and eastern Vermont. The ice
jam threat is above normal.

...Snow Depths and Water Equivalent...

Snow depths in the Adirondacks of northern New York and along and
east of Vermont`s Green Mountains were 10 to 20 inches at
elevations above 1500 feet with higher amounts near the summits.
In the valleys, 6 inches or less was observed at 1000 feet and
below. The deeper snow continues to be more widespread in the
Northeast Kingdom. The Lake Champlain and St. Lawrence Valleys had
four inches or less.

Snow water equivalents, or the amount of water held by the
snowpack, were 1 to 3 inches in the valleys of the Adirondacks and
eastern Vermont, and 3 to 6 inches in the higher terrain, mainly
above 2000 feet. Isolated mountain summits had 6 inches to a foot
of liquid in the snow pack. The Lake Champlain and St. Lawrence
valleys had zero to two inches of water equivalent in the snow
pack.

Snow depth and water equivalent were below normal for late January.

...River and Soil Conditions...

River flows are generally running near to above normal with river
ice firmly in place across northern New York and northern
Vermont, although, mild temperatures have prevented very thick
ice from forming. Periodic warmups have broken up river ice, with
minor jams and blockages from ice on northern rivers such as the
Au Sable.

Soils are generally frozen, with ground frost sensors showing
frost depths up to seven inches deep.

Long term precipitation deficits continue with a majority of the
North Country being in moderate drought. Recent snowmelt and
liquid precipitation events have increased stream flows and soil
moisture as river flows continue to run near to above normal.
Ground water levels continue to be low. USGS monitoring wells show
most ground water levels across the North Country being below
normal and much below normal, especially in the Champlain Valley
and in east-central Vermont.

Lake Champlain continues to trend below normal by about a half
foot. Based on the present snow pack conditions there is a low
probability of Lake Champlain flooding this spring, however it is
too early to make an accurate assessment for the lake.

...Weather Outlook...

An active weather pattern with above normal temperatures is
expected. A chance for light rain starts the weekend off Friday
night into Saturday. A more significant low pressure system will
bring the potential for a wintry mix early next week. This looks
be followed by a quick moving low providing the potential for
snow showers. Mid-level troughiness will continue to affect the
Northeast through the end of January with several chances for
precipitation.

The NWS Climate Prediction Center`s outlooks for the next three
month indicated better chances for above normal temperatures and
near normal chances for precipitation.

...Summary...

The winter/spring flood potential continues to be near normal.
Much of the area is under a normal flood threat based on snowmelt
and ice jams, with a below normal flood threat for the Champlain
Valley. It is still early in the season however, and additional
snowfall can change the flood risk.

It is important to note that heavy rainfall on top of snowmelt is
the driving factor in spring flooding, and flooding can occur
with little or no snow on the ground.

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

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

$$

KM



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