Flood Potential Outlook
Issued by NWS

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Winter/Spring Flood Potential Outlook
National Weather Service Pittsburgh PA
742 PM EST Fri Jan 5 2018

..WINTER/SPRING FLOOD OUTLOOK THROUGH JANUARY 19TH...

The flood potential is normal in the Ohio Valley.

A normal risk for flooding means that occasional flooding could
occur with water levels having minor impacts.

For the long-range river outlooks and the probability of
exceeding flood stage or the chances of flooding relative to
normal at specific forecast points during the next 90 days...refer
to www.weather.gov/ohrfc and click on the 90-day river outlook on
the left hand side of the page. Click on flood chc vs normal to
view the risk of flooding with respect to normal.

Flood outlooks are issued bi-weekly by the national weather
service during winter and early spring to summarize basin
hydrometeorological conditions and to assess the potential for
winter/spring flooding. The outlooks are based on current and
forecast conditions during the outlook period.

In addition...a 90-day water resource outlook is issued monthly.

Factors considered in assessing flood potential are (1)
antecedent conditions (2) past precipitation (3) recent
streamflows and reservoir levels (4) soil moisture (5) water
content of the snow pack (6) ice conditions on the rivers and (7)
future precipitation.

Meteorologically, since December 1st, winter has started out being
rather dry in the Ohio River Basin, with the exception of heavy
lake-effect snow downwind of Lake Erie. Here, snow water
equivalents are in the 2 1/2 to 3 inch range.

Another problematic effect of the arctic outbreak has been the
quick icing of rivers and streams in the Upper Ohio Valley
including, but not limited to the Allegheny, Monongahela, and
upper Ohio, where sub-zero temperature has had a flash freeze
effect.

Model output for the next ten days indicates a more active large-
scale pattern/storm track than in December. Both the GFS and
ECMWF produce precipitation totals of 1-2 inches for the ten day
period, but the ECMWF is the warmer of the two models.

Considering the uncertainty, the flood risk for this time frame
remains near normal.

$$
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