Spring Potential Flood Outlook For Northern & Eastern Maine

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
803 AM EDT Fri Mar 20 2020

...SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN... CENTRAL...AND
DOWNEAST MAINE...

This is the sixth Winter/Spring Flood Potential Outlook for 2020,
issued by the National Weather Service in Caribou, Maine. This
outlook is for Northern, Central, and Downeast Maine for the two-
week period of March 19th through April 2nd, 2020.

The flood potential for open water flooding and flooding due to
ice jams, remains near normal for this time of year, with the
exception of Northern Maine, where the flood potential is
slightly above normal.

...CLIMATOLOGICAL GUIDANCE...

A few storm systems affected the region over the last two weeks
bringing measurable snow and rain to the region. The most
significant storm system came across the region on March 13th
which brought 4 to 8 inches of snow across northern and central
areas. The central areas saw the snow change to rain as
temperatures warmed into the 40s. This storm helped add to the
snowpack across Northern Maine. The Bangor and Downeast region
have been below normal in regards to precipitation including the
snowfall. So far this month, Bangor has only recorded a trace of
snow. The snowpack, especially from Bangor to the coast has
decreased due to the mild temperatures over the last two weeks.

Temperatures over the last two weeks continued to average above
normal. Bangor recorded a high temperature of 53 degrees on the
9th, while across Northern Maine, temperatures topped out in the
upper 20s on that date. Over the last two weeks, there were a few
mornings, where temperatures dropped into the single numbers
across Northern Maine wih a few sites across the St. John Valley
into the Allagash region dropping below zero. Caribou recorded a
low temperature on the 16th of 4 degrees, while Frenchville
had a morning low of 3 degrees. The coldest spot that morning was
Big Black River with a morning temperature of -15.

The weather pattern over the next 5 to 10 days will continue to be
fairly active with a frontal system bringing some rain today
along with mild temperatures. Colder temperatures will return for
this weekend with temperatures being below normal. Another system
could affect the region on the 24th with some snow across the
northern and western areas and rain or snow further south. This
all depends on the track of the low that is expected to move out
of the Ohio River Valley. Another storm system could affect the
region by the end of next week which could bring snow or rain to
the northern areas and rain for the southern areas. There is still
alot of uncertainty with these two possible events. The track of
the storms will be key as to what type of precipitation the region
receives.

The official National Weather Service 6 to 14 day outlook
is calling for a continuation of near to above normal
temperatures and slightly above normal precipitation.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...

As of 7 AM Thursday morning, snow depths ranged from 28 to 42
inches across Northern and Northwest Maine, with Allagash
reporting 42 inches of snow on the ground. The NWS office in
Caribou reported 31 inches of snow depth. Chimney Pond in the
Baxter State Park region, reported a snow depth of an incredible
54 inches. Snow depths across the Maine Central Highlands
decreased with the milder temperatures. Snow depths in this region
ranged from 7 to 16 inches. Snow depths across the Bangor area
and Interior Downeast region ranged from a trace to 3 inches, with
most of this being in wooded areas. The coastal areas had no
snow.

Snow depths across Northern Maine averaged near to slightly above
normal for mid March, while across the Maine Central Highlands,
snow depths remained near normal. From Bangor to the coast, snow
depths continued to be below normal.

The snow water equivalent, or the amount of water contained in
the snowpack increased some more across the region over the last
two weeks. Northern and Northwest Maine recorded 9 to 12 inches
of water in the snowpack. Across the Maine Central Highlands, snow
water equivalents were in the range of 4 to 7 inches, while from
Bangor to the coast, 1 to 2 inches of water was measured in the
snowpack.

The snow water equivalent is now above normal across Northern and
Northwest Maine. Across the Maine Central Highlands, water
equivalents remain near normal. Water equivalents from Bangor to
the coast are below normal.

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

Soil moisture continue to be near normal for the entire region,
with the exception for Northwest Maine, where soil moisture was
above normal. The latest Palmer Drought Severity Index, which
measures soil moisture in the longer term, continues to show near
normal conditions.

A look at the groundwater levels, courtesy of the USGS, shows levels
are near normal across the region, with some indications of levels
dropping below normal across the Downeast region. This is
attributed to the lack of snow cover and significant precipitation
over the last two weeks.

...RIVER AND ICE CONDITIONS...

River flows are near normal across the entire region. The
exception to this continues to be across Washington County along
the St. Croix River basin, where flows are approaching slightly
below normal levels.

As of 7 AM this morning, ice covers about 95% of the rivers and
streams across Northern and Northwest Maine. There are a few open
stretches on the St. John, Aroostook and Allagash Rivers. The Fish
River has many open sections and there are open sections along
the St. John River near the International Bridge in Fort Kent and
downstream toward Madawaska. The Piscataquis and Penobscot Rivers
had ice on them with 70% ice coverage. There are open sections on
the Penobscot River from Bangor up to Millinocket, and along the
Piscataquis River from Guilford to Foxcroft Academy. Across the
Downeast region which includes the St. Croix River, ice coverage
was reduced less than 60%. There are large sections of the St.
Croix River with open water.

Ice thicknesses ranged from 18 to 24 inches along the Aroostook
River with 20 to 25 inches of ice thickness on the St. John and
Allagash River. Ice thickness on the St. John River at Nine Mile
Bridge remains near 25 inches, while the Big Black River in
Northwest Maine, has ice thickness close to 30 inches. Ice
thickness along the Piscataquis and Penobscot River, is 6 to 12
inches. The exception to this was along the East Branch of the
Penobscot River at Grindstone, where the ice thickness remains at
15 inches. The Kingsbury Stream at Abbot in Piscataquis County
hung on to an ice thickness of 15 inches, but much of the ice has
broken up and moved. The ice thickness along portions of the St.
Croix River was estimated to be 3 to 7 inches in spots.

An ice jam remains in place on the Aroostook River in Fort
Fairfield. This ice jam is one mile long and remains in place
just upstream from the Fort Fairfield bridge. Bunched up ice
remains in place on the Aroostook River in the vicinity of
Washburn. Along the St. John River, ice remains bunched up from
the town of St. John to St. Francis.

Ice coverage and thicknesses are near normal across the entire
region.

...IN CONCLUSION...

Based on the above information, the flood potential for open water
and ice jam flooding remains normal, with the exception of
Northern Maine, as the flood potential is now slightly above
normal.

As always, 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,
April 2nd.

$$

Hewitt