Flood Potential Outlook
Issued by NWS Portland, ME

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Winter/Spring Flood Potential Outlook
National Weather Service Gray ME
534 PM EDT Thu Mar 16 2017

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK...

The flood potential is above normal for the time of year across
most of western Maine and northern New Hampshire. flood potential
is about normal for the time of year across southern New
Hampshire.

The potential for ice jam flooding has passed for the season in
southern New Hampshire and southern Maine and is near normal for
northern New Hampshire and the mountains of Maine.

This is the sixth in a series of regularly scheduled flood
potential outlooks that are issued during the winter and spring
seasons. These outlooks will be issued every two weeks until the
end of the snow melt season, and will assess the potential for
flooding based on a number of factors.

...CLIMATOLOGICAL GUIDANCE...

After a colder than normal December and a very warm January that
saw average temperatures 7 to 8 degrees above normal, February
ended quite warm with temperature departures ranging from 3 to 6
degrees above normal. All but 5 days of February were above normal
in Portland. The wild temperature swings that occurred in previous
months have continued in March. The first 2 days of the month were
15 to 20 degrees above normal, then only 2 days later 15 to 20
degrees below normal. two of the coldest days this winter occurred
on March 4 and 11. We have seen a fairly active weather pattern
with several intense storms moving through New England since the
beginning of February. The weather pattern should still remain
active with several chanceS for light to moderate precipitation
over the next 2 weeks. The next system to affect the region
with potentially significant precipitation will be around March
25.

The official National Weather Service 6 to 10 day forecast calls for
below normal temperatures and near normal precipitation. The 8 to 14
day forecast calls for below normal temperatures and above normal
precipitation.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENT...

...NEW HAMPSHIRE...

Snow depth in southern New Hampshire range from 10 to 18 inches
with locally amounts. From central New Hampshire north to the
Canadian border snow depth ranges from 16 to 30 inches. Above
about 2000 feet from the White Mountains north snow depth is
generally greater than 3 feet. At Moose Falls near the Canadian
border snow currently stands at 47 inches.

Snow water equivalent /SWE/ in southern New Hampshire is on the
order of 1 to 3 inches with locally higher amounts. From central
New Hampshire to the Canadian border snow water equivalent ranges
from 3 to 8 inches. Above 2000 feet SWE ranges from 6 to 12 inches
with locally higher amounts. Moose Falls near the Canadian border
is reporting SWE of 14.5 inches.

Snow depth and water equivalent is below normal for the time of
year in southern New Hampshire and above normal in northern
areas.

...WESTERN MAINE...

Snow depth ranges from 8 to 20 inches near the coast, up to 18 to
24 inches through the foothills and 24 to 36 inches from the
mountains to the Canadian border.

Snow water equivalent /SWE/ is is running from 2 to 4 inches near
the coast to 4 to 7 inches through the foothills up to 7 to 10
inches with locally higher amounts from the mountains to the
Canadian border.

Snow water equivalent are about normal at the coast and above
normal in the mountains.

...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...

Soil moisture anomaly maps indicate that soil moisture is above
normal in northwest Maine and northern New Hampshire. Soil
moisture is normal elsewhere except below normal in southwest New
Hampshire.

The long term term Palmer Drought Severity Index shows normal
conditions across Maine and New Hampshire.

Reservoirs in the Kennebec River basin are above normal for the
time of year.

Reservoirs in the Androscoggin River basin are 51.4 percent full
which is 21.3 percent above normal.

At the end of February First Connecticut Lake in northern New
Hampshire was 191 percent of normal and 54 percent full. Lake
Francis was 169 percent of normal and 67 percent full. Lake
Winnipesaukee was 87 percent of normal and 76 percent full.

Groundwater levels courtesy of the USGS show a mix of above and
below normal groundwater. However at this time there is enough
water stored in the snowpack to see a normal recharge this
spring.

...RIVER AND ICE CONDITIONS...

River flows are come down to near normal levels for the time of
year due to colder temperatures. In southern New Hampshire
streamflow has fallen to somewhat below normal levels.

Ice jam flooding is no longer a threat in southern New Hampshire
or southern Maine. Farther north ice cover is again becoming
established due to the colder weather. There are also ice jams on
the Carrabassett and Sandy Rivers as well as the Swift River.
Ice jam flooding is still possible in northern locations.

...IN CONCLUSION...

Based on the above information the flood potential is above
normal for the time of year across western Maine and northern New
Hampshire and near normal in southern New Hampshire.

The potential for ice jam flooding has passed for the season in
southern New Hampshire and southern Maine and is near normal for
northern New Hampshire and the mountains of Maine.

It is important to note that major flooding does not occur from
snowmelt alone. Rainfall, how much and in how short a period of
time is the most important factor in determining the severity of
flooding.

Another Winter/Spring Flood Potential Outlook will be issued by
8 AM Friday March 31.

$$

TFH



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