Flood Potential Outlook
Issued by NWS Burlington, VT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FGUS71 KBTV 050144
ESFBTV
NYC019-031-033-089-VTC001-005-007-009-011-013-015-017-019-021-023-
027-070145-

Winter/Spring Flood Potential Outlook
National Weather Service Burlington VT
844 PM EST Thu Jan 4 2018

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

This is the first flood outlook for the 2018 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 threat of flooding due to snowmelt is near normal, though it is
below normal in the immediate term. The threat for ice jams is
near normal.

...Snow Depths and Water Equivalent...

As of Thursday morning, snow depths across the North Country were
near to slightly above normal, with the exception being the
higher elevations of the Adirondacks and northern Green Mountains,
which had less snow cover than normal. The wider valleys
generally had 6 to 12 inches of snow on the ground, while the
higher elevations had 1 to 2 feet. These amounts do not include
the snow that is currently falling across the region; depths will
likely be near to above normal once this ongoing event ends.

Snow water equivalents, or the amount of water contained in the
snowpack, were likewise near to a bit above normal away from the
higher terrain. SWEs were 1 to 2 inches in the Champlain and Saint
Lawrence Valleys, while elsewhere the snowpack had 2 to 4 inches.
The highest peaks were locally higher, with perhaps up to 6
inches of water in the snow cover.

...River and Soil Conditions...

Streamflows were near to above normal over much of the area; only
the northern Green Mountains were reporting flows below normal for
early January. Given the recent spate of cold weather, and with
no significant mild spells in sight, river flows are expected to
hold steady or fall over the next few weeks.

The recent cold weather has also allowed river ice to grow and
strengthen across the region. Average thicknesses and coverage are
greater than normal for this time of year due to the persistent
cold. Some freeze up jams were reported on the Salmon River near
Malone, New York, but no other areas of concern have been noted.

The ground is frozen across much of the region, especially in
those areas that have had relatively thin snow cover. Near-surface
soil moisture states are near normal for much of the region,
except the Champlain Valley where states are drier than normal.
The Palmer Drought Severity Index, which looks at moisture levels
in the longer term of weeks to months, shows very moist conditions
in the Saint Lawrence Valley, while the Adirondacks and Champlain
Valley are unusually moist. Areas along and east of the Green
Mountains have near normal long-term soil moisture states. This is
a reflection of the autumn months in which the Saint Lawrence
Valley saw more precipitation than normal, while the remainder of
the region was near to below normal.

Groundwater wells, courtesy of the USGS, are near to below normal
across the region. Indeed, wells along the New York side of the
Champlain Valley are reporting levels well below normal.

...Weather Outlook...

The current snow event will gradually wind down through Friday,
only to be followed by another blast of bitterly cold air through
the end of this week. A gradual moderating trend is expected
thereafter as the jet stream shifts back north. However, the
pattern will remain active, though exact timing and placement of
storm systems and their respective precipitation is hard to
pinpoint at this time. Systems are expected to be fairly
progressive, with a threat of precipitation every few days.

The official 6-14 day outlook for January 10 to January 18 issued
by the Climate Prediction Center matches the above thinking well,
calling for equal chances of warmer or colder temperatures along
with better chances for wetter than normal conditions through the
period.

...Summary...

Based on the above information, the winter/spring flood outlook
for open water flooding due to snowmelt and runoff is near normal
over the next couple of weeks, though it is below normal in the
near term. Snow depths are near to only slightly above normal at
worst, as is the water contained in the pack. While the pattern
will remain active, bitterly cold air will limit any snowmelt or
runoff through the end of this week. Therefore, river levels will
hold steady or gradually recede during this time. Temperatures
will moderate as we head through next week, and the active pattern
will likely add to the snowpack. While no significant runoff
events are anticipated, this does indicate a near normal threat
for open water flooding.

The threat for flooding due to ice jams is near normal for the
next couple of weeks. While river ice coverage is thicker and more
extensive than normal, there are no signs that point to the
potential of any sort of ice movement or breakup. However, the
rivers will need to be monitored for any freeze-up jams,
especially since very cold temperatures will return over the next
couple of days.

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.

The next Winter/Spring Flood Outlook will be issued on Thursday,
January 18, 2018.

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

$$

Hastings


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.