Winter/Spring Flood Potential Outlook For Northern & Eastern Maine - 01/07/2021
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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
902 PM EST Thu Jan 7 2021
...SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN... CENTRAL...AND
DOWNEAST MAINE...
This is the first Winter/Spring Flood Potential Outlook for 2021,
issued by the National Weather Service in Caribou, Maine. This
outlook is for Northern, Central, and Downeast Maine for the
two-week period of January 7th to January 21st, 2021.
The flood potential for open water flooding and flooding due to
ice jams is near normal for this time of year.
...CLIMATOLOGICAL GUIDANCE...
November 2020 came in well above normal for temperatures across
the region. As for snowfall, Northern Maine and the Maine Central
Highlands came in below normal, while the lower Penobscot Valley
including the Bangor region, came in slightly above normal. The
coastal areas were below normal for snowfall. The largest snowfall
event came on the 15th and 16th as the St. John Valley picked up 7
to 8 inches. The bigger story was the above normal temperatures
with unseasonably warm temperatures from November 6th through the
12th. Record warmth hit during a stretch from the 9th through the
12th, with a number of sites seeing all time record highs for the
month. Caribou recorded a record high temperature of 75 degrees on
the 10th, which set an all time record high for the month. Houlton
and Millinocket also set all-time record highs for the month on
the 10th with 75 degrees and 74 degrees respectively. The warm
and wet weather at the end of the month significantly reduced the
snowpack across the region.
December 2020 followed with a continuation of above normal
temperatures, but there were was a stretch from the 15th through
the 19th, when temperatures were below normal. As a matter of
fact, Caribou and other sites across Northern Maine had at least 4
nights when the low temperatures fell below zero. A few snow
events helped to bring the snowpack up some during the month, and
the cold stretch helped to keep the snowpack in place. The
Northern Maine region saw the monthly snowfall reach above normal
with Caribou recording 26.3 inches of snow for the month, which
was 2.6 inches above normal. A different story however from the
Maine Central Highlands down across the Downeast region, as
monthly snowfall was well below normal. Bangor only recorded 5.7
inches for the month, which was 8.7 inches below normal. In
regards to the above normal temperatures, December 1st came in
with record high temperature of 60 degrees in Caribou and some
heavy rainfall. The high temperature was a record for the day and
month. Colder air returned with a few snow events to help build up
a snowpack, especially across Northern Maine and the Maine
Central Highlands. This snowpack was wiped out across Northern
Maine and the Maine Central Highlands on December 25h, Christmas
Day, due unseasonably warm temperatures and rain. Record high
temperatures were set that day across many locations including
Caribou and Bangor. This event helped break up the ice on the
rivers with many rivers and streams seeing the ice being flushed
out. Some flooding did occur along the Piscataquis River at Dover-
Foxcroft back on the 1st and again on the 25th.
January 2021 started out above normal for temperatures with one
significant snow event that occurred back on the 2nd, with
Northern Maine seeing anywhere from 4 to 9 inches, while across
the Maine Central Highlands and the Downeast region, 7 to 12
inches of snow was measured.
A fairly benign weather pattern looks to be in store for the
region over the next 5 to 10 days with a few weak systems
bringing some light snow to the region. No significant storm
system are expected during this timeframe.
The official National Weather Service 6 to 14 day outlook is
calling for above normal temperatures and near to slightly below
normal precipitation.
...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...
Snow depths ranged from 5 to 8 inches across Northern Maine, while
the Maine Central Highlands, including the Bangor region, have 6
to 12 inches of snow. The Downeast region, including the coast,
recorded 2 to 5 inches of snow depth. Snow depths were below
normal for early January.
The snow water equivalent, or the amount of water contained in
the snowpack is the highest across northern and central areas
with 1 to 2 inches of water being recorded. Across the Downeast
and the coast, water equivalents were on the order of a trace to 1
inch.
The snow water equivalent are well below normal for this time of
year.
...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...
Soil moisture was near to slightly above normal across the region,
especially for northern and central areas.
The latest Palmer Drought Severity index, which measures soil
moisture in the longer term, showed near normal conditions.
A look at the groundwater levels, courtesy of the USGS, showed
near to above normal across northern and central areas, with near
normal levels for the Downeast region, including the coast.
...RIVER AND ICE CONDITIONS...
River flows were near to slightly above normal across the region for
this time of year.
After a warm November and December, colder temperatures have
allowed some ice to form on the streams and rivers, especially
across Northern Maine. The warmup and heavy rainfall event that
occurred on the 25th, allowed for ice that was in place to break
up and flush out. All the rivers by the 26th were flowing freely
of ice. The exception to this is along the Aroostook River in
Fort Fairfield, where the ice broke up and pushed east toward New
Brunswick. The ice then locked up just north of the Fort
Fairfield bridge as colder air moved in later in the day on the
26th. This ice jam remains in place and has expanded further west
toward the Caribou-Fort Fairfield line. This ice jam is about 7
miles long with ice thickness estimated to be 6 to 12 inches.
There is some open water flowing along the side of the jam.
The colder air that followed after the 26th, along with some snow
had allowed another small ice jam to set up on the St. John
River, in the town of Grand Isle. The ice thickness with this jam
was estimated to be around 6 inches. Water was flowing along the
sides of this jam.
Ice coverage and thicknesses were below normal for early January.
...IN CONCLUSION...
Based on the above information, the flood potential for open water
flooding is near normal across the region at this time. The threat
for ice jam flooding is near normal for early January, especially
across the northern rivers.
It is important to remember that a heavy rainfall event along
with mild temperatures can lead to an increased potential for
flooding with snowmelt and runoff. Ice breaking up and jamming can
elevate the threat for flooding in a short period of time.
The next Winter/Spring Flood Outlook will be issued on
Thursday, January 21st.
$$
Hewitt
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