Flood Potential Outlook
Issued by NWS Burlington, VT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
913
FGUS71 KBTV 260603
ESFBTV
NYC019-031-033-089-VTC001-005-007-009-011-013-015-017-019-021-023-
027-280615-

Winter/Spring Flood Potential Outlook
National Weather Service Burlington VT
203 AM EDT Thu Apr 26 2018

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

This is the ninth 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 snow
melt and break up of river ice across central and northern Vermont
and northern New York.

...Overview...

The spring flood potential for open water flooding due to snowmelt
and/or rainfall is near normal for all of northern New York and
northern and central Vermont, excluding the Northeast Kingdom.
Portions of the Northeast Kingdom have a slightly above normal
potential for open water flooding.

The threat for ice jam related flooding has passed for the season
for our entire forecast area.

...Snow Depths and Water Equivalent...

Across Vermont, most of the snow has now melted away below 1500 ft
or so. Some snow cover still exists along the spine of the Green
Mountains and in the Northeast Kingdom. Snow depths of up to 1 to 2
feet have been reported in these areas, fairly isolated and above
2000 ft. This deeper snow pack contains as much as 4 to 8 inches of
snow water equivalent. Snow depths and the amount of water contained
in the snow pack are near normal for late April.

Much like Vermont, northern New York has little snow at the lower
elevations, with some of the Adirondack valley locations having as
much as 6 inches below 1500 ft. Above this level, snow depths of 6 to
12 inches are common with higher amounts in the higher peaks. Snow
water equivalents are mainly an inch or less, though the higher
terrain has 3 to 6 inches of water contained in its snow cover.
Again, this is near normal for this time of year.

...River and Soil Conditions...

The cold and unsettled conditions we experienced through much of
April has kept things relatively wet. The colder weather also
delayed snowmelt a bit and green up is running a bit behind
schedule. The wettest conditions across our forecast area exist in
northern New York where the latest Palmer Drought Index is showing
moderately moist soil states. Elsewhere the longer-term soil
moisture, as indicated by the Palmer Drought Index, is near normal.

Likewise, a look at the groundwater monitoring wells across the
region, courtesy of the USGS, shows that groundwater is near normal
in Vermont. Meanwhile, a wide array of conditions exist in northern
New York, where wells are indicating below normal to much above
normal water levels.

River flows across both Vermont and northern New York are near to
above normal for late April. This seems reasonable given the wet
pattern we have been in, and the recent warmer weather and resultant
snowmelt. Flows will remain somewhat high through the weekend as we
remain under a rainy pattern, but drier and warmer weather will
return next week, allowing flows to subside.

...Weather Outlook...

As mentioned above, we have been plagued by cold and showery weather
through much of April, with just a few days of recent warmth to
serve as a tease. We will remain under the influence of an upper
trough through the weekend; hence cooler and wetter conditions will
prevail into early next week. Thereafter, a large scale pattern
shift appears to be on the horizon as forecast guidance indicates a
building upper level ridge and southwesterly flow aloft. This will
bring another break from the rain as well as allow temperatures to
warm to well above normal through at least the middle part of next
week. Thereafter, more upper level troughiness will take hold, but
this should be more transient.

The official National Weather Service 6 to 14 day outlook for April
30 through May 8 matches the above thinking, calling for
temperatures to average well above normal across all of the
Northeast CONUS. Precipitation for the same time period will be
below normal, perhaps trending more towards normal in the longer
term.

...Summary...

Based on the above information, the threat for open water flooding
due to snowmelt and runoff is slightly above normal in the Northeast
Kingdom. River flows are mostly above normal, soil moisture states
are near normal, and there is still a decent amount of snow water
available for melt runoff into area rivers and streams. Periods of
rain are expected over the next several days, and this will serve to
increase river flows even more. This flood threat is highest in the
near term as warmer and drier weather is anticipated to move in early
next week.

Elsewhere, the spring flood potential is near normal. Although river
flows, soil moisture states, and groundwater levels are near or
above normal, there is limited snow water available for melt runoff
into area waterways. Without the added runoff potential from melting
snow, it would take a very heavy rainfall event to induce flooding
for much of our area. Since we do not currently see much potential
for such an event in the foreseeable future, a near normal flood
threat seems reasonable.

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.

Barring a major late season snow event over the next two weeks, this
will be the last winter/spring flood potential outlook issued by the
National Weather Service office in Burlington for this season.

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.