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