Flood Potential Outlook
Issued by NWS Caribou, ME

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HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
354 PM EST Fri Jan 5 2018

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

This is the first Winter/Spring Flood Potential Outlook for 2018,
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 4th to January 18th, 2018.

The flood potential for open water flooding and flooding due to
ice jams is near normal for this time of year.

...CLIMATOLOGICAL GUIDANCE...

An arctic airmass invaded the Northern New England region with a
prolonged period of very cold temperatures for Northern and
Downeast Maine. This arctic airmass started in mid December 2017
and continued right into the first week of January 2018.
Temperatures for the month of December averaged 4 to 7 degrees
below normal.

A series of low pressure systems moved up along the Maine coast
bringing some significant snowfall to the region. The highest snow
depths were across northern and central areas with 12 to 18
inches being reported.

The overall pattern looks like it will shift as the cold airmass
currently across the region looks as though it will retreat into
Canada. This will allow for a moderation in temperatures by the
by late next week.

The official National Weather Service 6 to 10 day and 8 to 14 day
outlook is looking at above normal precipitation and near normal
temperatures.

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

Snow depths ranged from 12 to 18 inches across Northern and
Central Maine with some isolated spots such as the Moosehead Lake
region coming in with 18-24 inches. The Downeast region including
the coast recorded 6 to 12 inches of snow depth. This is slightly
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 3 to 4 inches of water being recorded. Across the interior
Downeast region to the coast, 1 to 3 inches of water was common
in the snowpack.

The snow water equivalent is near normal for this time of year.

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

Soil moisture was near normal across the region. The latest
Palmer Drought Severity Index, which measures soil moisture in the
longer term, was showing near normal conditions.

Looking at the groundwater levels, courtesy of the USGS, we see
the levels were near normal with the exception of the Acadia
region where levels were slightly below normal. This is an
improvement from October and November where groundwater levels
across Downeast including the Acadia region, were below normal.

...RIVER AND ICE CONDITIONS...

River flows appeared to be near normal for this time of year
throughout the region.

The very cold temperatures over the last 2 to 3 weeks have allowed
ice to form fairly quickly on all rivers. Rivers and streams
across the region are now full of ice with some rivers totally
ice covered. The exception to this was on the St. John River
between Madawaska and Grand Isle as some open water was seen. Ice
coverage and ice thickness was slightly above normal. Ice thickness
was estimated to range from 8 to 14 inches across the northern
rivers including the St. John, Allagash and Aroostook Rivers while
the Piscataquis and Penobscot rivers showed 6 to 10 inches of
ice.

...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. 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 potential outlook will be issued by
the NWS in Caribou on January 18th.


$$

Hewitt



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