Flood Potential Outlook
Issued by NWS Caribou, ME

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
130 PM EDT Thu May 2 2019

This is the ninth Winter/Spring Flood Potential Outlook for 2019,
issued by the National Weather Service in Caribou, Maine. This
outlook is for Northern, Central, and Downeast Maine for the two-
week period of May 2nd to May 16th 2019.

The flood potential for open water flooding remains normal for
the entire region. There is no threat for ice jam flooding.

...CLIMATOLOGICAL GUIDANCE...

The last two weeks were active with a series of rain events. The
first event came in the region during the 19th and 20th, bringing
anywhere from 1.50 to almost 3 inches of rain to the region. The
heaviest rainfall was across the Maine Central Highland and
Northern Maine. This event led to rapid snowmelt and runoff,
allowing for rivers and streams to rise sharply, with some of them
overflowing their banks, leading to some minor flooding. This
event also caused ice to break up and jam on the St. John and
Aroostook River. The second rain event came on April 26 and 27th,
which brought 0.50 inches to 1.5 inches of additional rainfall,
which reduced the leftover snowpack and increased the runoff rate.
The heaviest rainfall occurred across the Piscataquis River and
southern Penobscot River basins. This event allowed already
swollen rivers and streams to rise again, leading to more minor
flooding. More on this in the River and Ice section below.

The official National Weather Service 8 to 14 day outlook is
calling for below normal temperatures with precipitation expected
to be near to slightly above normal.

The weather pattern over the next 7 to 14 days looks to remain
active. A storm system is expected to bring the potential for
some rain to the region on the 3rd into the 4th with amounts of
0.15 to 0.30 inches. Another rain event could to possibly affect
the region during the 8th and 9th. Some of the long range model
guidance was showing the potential for far northern areas, such
as the Allagash region, to receive some wet snow. There is a range
of solutions with the long range guidance on this possible event.
Therefore, confidence is low on the track and development of this
possible event. The rivers and streams around the region have
receded substantially over the last week due to the dry airmass
that has been in place. Therefore, the rivers and streams should
be able to handle the rainfall.

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

Snow depths across the Maine Central Highlands to the northern
border were reduced to just a few inches of snow, and most of
this was in the wooded areas. The was no snow left from the Bangor
region to the Downeast coast.

The snow water equivalent, or the amount of water contained in
the remaining snowpack was reduced to less than one inch.

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

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

Groundwater levels, courtesy of the USGS, were well above normal,
with some of the highest readings being across Northern and
Downeast Maine. Fort Kent came with its highest reading for late
April in 41 years of record. Kenduskeag came in with its highest
reading for late April since records began 39 years ago.

...RIVER AND ICE CONDITIONS...

River flows were near to slightly above normal throughout the
region with the highest streamflows across the Penobscot and St.
Croix River basins.

Ice that was left over in St. John and Aroostook River basins let
go during the heavy rain event back on the 19th and 20th. Along
the St. John River, some of the ice jammed up near Grand Isle and
the town of St. John, which led to some minor lowland flooding. On
the Aroostook River, an ice jam extending from Washburn
downstream to the vicinity of Crouseville, let go late at night on
the 20th. This led to some minor flooding along portions of Route
164 and Gardner Creek Road.

The flood threat turned to open water flooding on the river
basins. The Mattawamkeag River at Mattawamkeag went above flood
stage and crested at 15.7 feet on the 24th. Flood stage is 13.5
feet. Some flooding occurred along the Bancroft Road. The river
has since receded below flood stage due the latest dry spell.
Other rivers such as the St. John and Fish Rivers at Fort Kent
went above flood stage, with some minor flooding reported. These
two rivers receded below flood stage in the last week, in
response to the latest dry spell

...IN CONCLUSION...

Based on the above information, the flood potential for open
water is near normal for the entire region.

It is important to remember that a heavy rainfall event along
with mild temperatures can lead to an increased potential for
flooding with runoff.

This will be the last Winter/Spring Flood Potential Outlook for
the season.

$$

Hewitt


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