Flood Potential Outlook
Issued by NWS Burlington, VT

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Winter/Spring Flood Potential Outlook
National Weather Service Burlington VT
1030 AM EST Thu Feb 15 2024

...Winter/Spring Flood Potential Outlook...
This is the fourth flood outlook for the 2024 winter/spring flood
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/formation of river ice
across northern and central Vermont and northern New York. This
outlook is valid for the two week period of February 15-29, 2024.

...Overview...
The potential for open water flooding through the end of February
is below normal for southern Vermont and the St. Lawrence Valley
of New York. Elsewhere, across the Adirondacks and central and
northern Vermont the open water flooding threat is normal. Only
minimal amounts of river ice are present, and mainly across far
northern watersheds near the international border, leading to a
well below normal threat for ice jams in most areas.

The overall weather pattern during the first half of February was
one of unseasonable warmth with persistent dryness as the polar
jet stream retreated northward and remained unphased with the
southern stream jet. In fact, through February 14, overall mean
temperature departures for the month were running an incredible 8
to 14 degrees above long term climatological norms across the NWS
Burlington service area. Burlington, VT, for example, showed a
14-day mean temperature departure of +11.8 degrees while Massena,
NY had a mean positive departure of +13.8 degrees. Given the
overall dryness, mean precipitation departures largely ran on the
negative side of normal through the first half of the month with
most observing sites recording less than one quarter inch of
liquid. Saranac Lake, NY, for example, only measured 0.05 inches
of precipitation through the 14th while Springfield, VT measured a
scant 0.01 inches. Not surprisingly, snow totals through the
first two weeks of the month were well below normal, with most
observing sites recording just a few inches, at most, and mainly
in the northern mountains. Many spots of the Champlain Valley
observed bare ground for much of this stretch.

The following is a summary of the conditions by region as of
Thursday morning, February 15, 2024:

...St Lawrence Valley...
.Flood Risk...Below normal
.Snow Cover...Below normal, 1 to 3 inches
.Water Equivalent...Below normal, less than 1 inch
.Streamflows...Above normal, 76th-90th percentile
.Soil state...Above normal wetness
.Groundwater...Near normal, 25th-75th percentile
.River Ice...Some thin ice noted, but generally below normal
 thickness

...Northern Adirondacks...
.Flood Risk...Near normal
.Snow Cover...Below normal, ranging from 6 to 16 inches, with
 2-4+ ft in the High Peaks above 3,000 feet
.Water Equivalent...Below normal, 1 to 4 inches, with 5+ inches
 in the High Peaks above 3,000 feet
.Streamflows...Above normal, 76 to 90th percentile
.Soil state...Above normal wetness
.Groundwater...Above normal, 76th to 90th percentile
.River Ice...Some thin ice noted, but below normal thickness

...Champlain Valley...
.Flood Risk...Near normal
.Snow Cover...Below normal, trace to 3 inches
.Water Equivalent...Below normal, less than 1 inch
.Streamflows...Near to above normal, 50th to 90th percentile
.Soil state...Above normal wetness
.Groundwater...Above normal, 76th to 90th percentile
.River Ice...Minimal coverage

...Central/northern Green Mountains and Upper CT River Valley...
.Flood Risk...Near normal
.Snow Cover...Below normal. Values ranging from 6 to 16 inches,
with 2-4+ feet above 3,000 feet
.Water Equivalent...Below normal, ranging from 1.5 to 4.5 inches,
with 5+ inches above 3,000 feet
.Streamflows...Near to above normal, 50th to 90th percentile
.Soil state...Above normal wetness
.Groundwater...Above normal, 76th to 90th percentile
.River Ice...Patchy ice cover, with highest coverage north.

...Southern VT and the adjacent Connecticut River Valley...
.Flood Risk...Below normal
.Snow Cover...Below normal, 1 to 5 inches in the CT River Valley
and 6 to 12 inches in the mid terrain. At higher elevations,
values average from 2-3+ feet
.Water Equivalent...Below normal, 2 inches or less in the CT River
Valley, 1.5 to 4.5 inches in mid-terrain, and 5+ inches above
3,000 feet
.Streamflows...Near to above normal, 50th to 90th percentile
.Soil state...Above normal wetness
.Groundwater...Above normal, 76th to >90th percentile
.River Ice...Minimal coverage

..Snow Depths and Water Equivalent...
The unseasonably warm and dry weather pattern which occurred over
the last week in January and the first two weeks of February led
to little snow across the NWS Burlington service area. As such,
negative snow depth departures noted in late January only trended
more negative. For example, Burlington, VT only recorded a trace
of snow depth or bare ground for the entire stretch from January
29 to February 13 leading to a negative yearly/winter departure by
that date of -27.9 inches. Snow water equivalents exhibited
similar trends, with all areas showing below normal values. Only
the higher elevations and summit areas observed values somewhat
closer to normal. For example, on February 14, Mt. Mansfield
observed a snow depth of 52 inches, which was 8 inches below the
normal of 60 inches for the date.

...River and River Ice Conditions...
Daily and multi-day averaged streamflows remain at or above
normal across the entire region. This is indicative of residual
interflow and runoff from December`s excessive precipitation,
though with recent dryness a continued slight downward trend in
levels has been observed over the past two weeks.

Given the recent warmth, only patchy ice, if any, has formed
across the region over the past few weeks with the most intact
coverage located across far northern watersheds such as along the
Missisquoi and St. Regis Rivers. However, even here, thicknesses
are well below normal and generally six inches or less with some
open leads. Further south, river ice coverage is considerably
less, and even scant to non-existent. This was confirmed along
stretches of the Winooski and Lamoille Rivers by NWS Burlington
river ice surveys during the first week of February. No ice jams
are currently reported.

...Soil Moisture and Groundwater Conditions...
Very moist to wet soil moisture conditions have persisted across
the region over the past two weeks, with latest CPC data
supporting mean values in the 70th to 90th percentile range. This
is supported by the latest groundwater data from the United States
Geological Survey showing most values in the upper quartile, or
76th to 90th percent range in all areas except the St. Lawrence
Valley where values were slightly lower.

...Weather Outlook...
As we progress into the back half of February, the latest long-
term model trends suggest a more active weather pattern will be
possible along with normal to slightly above normal temperatures.
This appears reasonable given the most recent forecasts of the
North Atlantic Oscillation and the Pacific North America Index.
The official 6 to 10 and 8 to 14 day outlooks from NOAA`s Climate
Prediction Center tend to agree and are indicating higher chances
of above normal precipitation and near to perhaps slightly above
normal temperatures. However, no large-scale, heavy rainfall
events are expected for the period giving confidence to the
outlook as a whole.

...Summary...
Based on the above meteorological and hydrological information
discussed above, the potential for open water flooding over the
next two weeks is below normal for southern Vermont and the St.
Lawrence Valley of New York. Elsewhere, across the Adirondacks and
central and northern Vermont the open water flooding threat is
normal. With little in the way of ice coverage and thickness on
area rivers, the overall threat of ice jam flooding is below to
well below normal through the end of the month.

It is important to remember that heavy rainfall can result in
flooding at any time of year, even in areas that have little or
no snow on the ground.

A graphic depicting the flood potential across the NWS Burlington
service area is available online at:

www.weather.gov/nerfc/springfloodpotential

The next Winter/Spring Flood Potential Outlook will be issued by
NWS Burlington on Thursday, February 29, 2024.

For access to current weather conditions and forecasts, please
visit our web site at www.weather.gov/btv.

$$

JMG


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