Winter/Spring Flood Potential Outlook For Northern & Eastern Maine - 03/04/2021
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MEC003-009-019-021-025-029-112215-
WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
509 PM EST Thu Mar 4 2021
..SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN... CENTRAL...AND
DOWNEAST MAINE...
This is the fifth 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 March 4th to March 18th, 2021.
The flood potential for open water flooding remains slightly
below normal across the entire region. The flood potential due to
ice jams remains near normal across the Northern Maine rivers,
while the Central and Downeast region is below normal.
...CLIMATOLOGICAL GUIDANCE...
There were several minor winter storms that moved across the
region the previous two weeks. These storms produced approximately
2-5 inches at a time across portions of the area.
There were a few shots of modified arctic air but no extreme cold
during the month. The coldest minimum temperature at Caribou was
minus 10 while Houlton dropped down to -11 on the 19th of
February. Caribou rose to as warm as 41F with Bangor rising to 45F
on the 24th of February.
The North Atlantic Oscillation (NAO) continues to trend neutral to
weakly positive. A neutral to slightly positive NAO favors more
zonal upper level flow with most of the arctic air locked up
across Canada with only brief intrusions into the northeast.
In addition, the Pacific North America (PNA) pattern is forecast
to be mainly negative heading into and through the middle of
March. With a negative PNA patter, upper level ridging is favored
across the southeast U.S. which tends to result in southwesterly
upper level flow across New England.
The official National Weather Service 6 to 14 day outlook is calling
for above normal temperatures and near to possibly above normal
precipitation.
...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...
Snow depths increased over the last two weeks across Northern
Maine into the Maine Central Highlands, while the Penobscot Valley
into the Downeast region saw a decrease in snow depths.
Snow depths ranged between 22 to 32 inches across Northern and
Northwest Maine, while the Maine Central Highlands recorded 14 to
21 inches of snow depth. As of 8 AM this morning, the NWS office
in Caribou had a 25 inch snow depth, while Winterville had around
32 inches of snow on the ground. Interestingly enough, Chimney
Pond in the Baxter State Park region reported 42 inches of snow on
the ground. Snow depths across the Penobscot Valley into the
Downeast region decreased to 2 to 8 inches.
Snow depths were near to slightly below normal across Northern
Maine and the Maine Central Highlands, while snow depths from
the Penobscot Valley into the Downeast region were below normal.
The snow water equivalent, or the amount of water contained in
the snowpack, increased over the two weeks across Northern Maine
and the Maine Central Highlands. Northern Maine was seeing 5 to 7
inches, while the Maine Central Highlands had 4 to 6 inches. The
NWS in Caribou recorded a snow water equivalent of 5.5 inches.
This is an increase of 2 inches over the last two weeks. The
highest snow water equivalent was reported in Winterville with 7.1
inches of water in the snowpack.
Snow water equivalents across the Penobscot Valley and the
Downeast region ranged from 1 to 3 inches.
Snow water equivalents are near to slightly below normal across
the region.
...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...
The latest Palmer Drought Severity index, which measures soil
moisture in the longer term, continued to show near normal
conditions, with Hancock County coast seeing slightly below
normal.
A look at the groundwater levels, courtesy of the USGS, showed
mainly near normal across the region. There were a few sites such
as Clayton Lake in Northwest Aroostook County and Amherst in
Hancock County, reporting below normal groundwater levels. There
still exists enough of a snowpack across the region that is
available for recharge.
...RIVER AND ICE CONDITIONS...
River flows were near normal across much of the region, with the
exception of the St. Croix River Basin, as flows were slightly
below normal.
About 95% of the streams and rivers across the region are snow
and ice covered, including the St. Croix River basin. Although,
there are sections of open water that exist, especially along the
Penobscot, Piscataquis and St. Croix Rivers.
Ice thicknesses ranged from 12 to 18 inches across the Aroostook
and St. John River basins, including the Allagash River. The
thickest ice was across the St. John River basin, which includes
the Allagash and Fish River with up to 18 inches of hard ice. The
Fish River saw an expansion of ice over the two last weeks, with
just a small stretch of open water in the Fort Kent region.
The Penobscot River remained iced in around the Bangor region for
approximately 3 miles, including where the Kenduskeag Stream
joins the Penobscot. Open water was noted north toward the Old
Town area, with some open areas as far north as the Millinocket
area. The East Branch of the Penobscot River at Grindstone was ice
covered with a couple of open stretches to the south. Ice
thickness was measured by the USGS to be 10-12 inches at
Grindstone, and along the stretch of Kenduskeag Stream meeting up
with the Penobscot River at Bangor. The Piscataquis River from
Blanchard to Dover-Foxcroft was ice covered with some open
sections along the sides, while some open water was noted toward
the Medford region. The USGS measured ice thicknesses of 8 to 14
inches on the Piscataquis River along the stretch from Blanchard
to Dover-Foxcroft.
There are some ice jams remaining in place. One bunched up jam
resides on the Aroostook River from just east of Caribou to the
Fort Fairfield bridge. This jam is approximately 7 miles in
length. The jam remains broken up in spots along this stretch. An
ice jam remains in place on the Allagash River near the bridge
where the Allagash River meets the St. John River. The ice jams in
Crouseville on the Aroostook River and near Lille on the St. John
River let go over the last two weeks with no issues.
Despite the ice coverage expanding over the last two weeks, ice
coverage and thicknesses remain below normal for this time of
year.
...IN CONCLUSION...
The flood potential for open water flooding is slightly below normal
across the entire region. The flood potential due to ice jams
remains near normal for the Northern Maine River basins. The flood
potential for ice jam flooding across the Piscataquis and
Penobscot River basins is below normal for this time of year.
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,
March 18th.
$$
Hewitt/Farrar
posted by Advackia at 1:16 PM
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