Flood Potential Outlook
Issued by NWS Cleveland, OH

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Winter/Spring Flood Potential Outlook
National Weather Service CLEVELAND OH
303 PM EST Thu Jan 4 2018

...INCREASED RISK OF ICE JAM FLOODING AS RIVERS AND LAKE ERIE SEE
A GROWTH IN ICE COVERAGE...ALSO AN ABOVE NORMAL FLOOD RISK IN THE
SNOWBELT OF NORTHEAST OHIO AND NORTHWEST PENNSYLVANIA DUE TO
HIGHER THAN NORMAL SNOWPACK...

This is the first winter flood potential outlook of the winter
season. Flood outlooks are issued every two weeks in the winter
and spring to highlight any risks for significant flooding. The
outlooks are based on the basin and forecast conditions. This
includes snow cover and water equivalent, creek and river levels
and the amount of ice on them, along with the expected conditions
during the next two weeks.

...CURRENT CONDITIONS SUMMARY...
In December the precipitation amounts were below normal supporting
slightly below normal stream levels. The last week of 2017 and
first week of 2018 has seen an arctic airmass over the Great Lake.
This dry airmass has kept precipitation amounts and temperatures
in the area below normal. The exception to this was record
breaking lake effect snow northeast Ohio and northwest
Pennsylvania. Parts of northwest Pennsylvania have seen snow
accumulations up to four feet deep at the time of this issuance.
This stored water has raised the flood risk for portions of Erie
and Crawford Counties in Pennsylvania.

Most of the area rivers and streams saw rapid ice growth over the
last two weeks, with continued growth over the next few days. As
the lake ice grows the flow at the mouth of the northerly flowing
rivers becomes restricted. The current streamflows remain at or
below normal. As ice thickness grows the risk of significant ice
jams increase. Communities prone to ice jam flooding should begin
monitoring the ice development and alert authorities and the
National Weather Service if any jams or jam related flooding
occurs.


The following is a summary of the conditions by basin with
measurable snowpack as of Thursday morning, January 4th:

...FRENCH CREEK / LAKE ERIE BASIN...
.SNOW COVER..........2 to 3 feet on average, upwards of 4 feet
.WATER EQUIVALENT....3 to 5 inches.
.CREEK FLOWS.........Normal.
.CREEK ICE...........Mostly frozen.
.GROUND STATE........Completely frozen.

...MAHONING RIVER / OHIO RIVER BASIN...
.SNOW COVER..........3 to 5 inches.
.WATER EQUIVALENT....0.5 to 1 inch.
.RIVER FLOWS.........Normal.
.RIVER ICE...........Mostly frozen.
.GROUND STATE........Completely frozen.

...GRAND RIVER / LAKE ERIE BASIN...
.SNOW COVER..........1 to 2 feet.
.WATER EQUIVALENT....3 to 4 inches.
.RIVER FLOWS.........Normal.
.RIVER ICE...........Mostly frozen.
.GROUND STATE........Completely frozen.


...CHAGRIN RIVER / LAKE ERIE BASIN...
.SNOW COVER..........18 to 24 inches.
.WATER EQUIVALENT....2 to 3 inches.
.RIVER FLOWS.........Normal.
.RIVER ICE...........Mostly frozen.
.GROUND STATE........Completely frozen.


...TEMPERATURE AND PRECIPITATION OUTLOOK...
The weather pattern will become more progressive with
warmer and wetter storm systems projected to move over the
region. This pattern could support minor to possibly moderate
river flooding conditions across the region. The pattern is
expected to remain active into the middle of January.

...FLOOD POTENTIAL OUTLOOK...
Flood risk during the next two weeks is above normal due to
increased snowpack in the snowbelt and ice growth on area rivers.
The warmer and wetter pattern is not projected to cause rapid
snowmelt or river rises at this time. The main threat will be from
any ice jams that develop and cause flooding. The dry nature of
the snowfall will allow for plenty of storage and compaction
before releasing runoff into the river basins. It would take a
notable rain event and/or warm up which is not projected at this
time.

...ADDITIONAL INFORMATION...
Real time river information and probabilistic forecast for
specific locations along rivers across the region can be found on
the internet at www.weather.gov/cle. Since conditions can change,
please refer to the latest flood watches, warnings, and
statements for additional information.


$$



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