Public Information Statement
Issued by NWS Sterling, VA

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NOUS41 KLWX 231322

Public Information Statement
National Weather Service Baltimore MD/Washington DC
922 AM EDT Thu Jun 23 2016

...New Flood Inundation Mapping coming soon to a portion of the
Potomac River...

Note the date of this implementation has been delayed by one week.
Further minor delays could occur. This statement will be re-issued
if any changes to the date occur.

Effective on or about the week of July 5, 2016 (exact date to be
determined), the National Weather Service (NWS) will add three new
flood inundation map libraries to the Advanced Hydrologic
Prediction Service (AHPS) web portal for portions of the Potomac
River. These are the first NWS inundation maps covering any
portion of the states of Maryland or Virginia, or the District of

These inundation map libraries show extent and depth of a
freshwater flood on the Potomac River from near Fletcher`s Cove in
Northwest DC to the mouth of Broad Creek in Prince George`s
County, Maryland, a distance of approximately 14 miles. Backwater
flooding of tributaries by the Potomac is also represented within
this reach, including on Cameron Run, Oxon Run, Four Mile Run, and
the Anacostia River.

Each inundation library is associated with a NWS river forecast
point, and extends north and south of each location. They will be
available for the following forecast locations:

* Potomac River at Georgetown/Wisconsin Avenue (GTND2)
* Washington Channel at DC Southwest Waterfront (WASD2)
* Potomac River at Alexandria (AXTV2)

For additional details on these map domains, visit

Inundation maps provide information on the spatial extent and depth
of flood waters in the vicinity of these forecast points. Users will
be able to display flood inundation maps for various levels ranging
from minor flooding to well above the largest observed flood. An
option is also available to display the map most closely related to
the current forecast.

Flood inundation maps, combined with river observations and NWS
forecasts, enhance the communication of flood risk, provide users
with additional information to better mitigate the impacts of
flooding, and build more resilient communities.

These flood inundation maps and associated geospatial data
(shapefiles) will be available on or about the week of July 5,
2016 (exact date to be determined) through the AHPS portal at:

A users guide for the flood inundation map web interface is
available at:

These inundation maps were developed as an interagency project of
the District of Columbia Silver Jackets team, made up of the
Philadelphia and Baltimore Districts of the U.S. Army Corps of
Engineers, the United States Geological Survey (USGS), the
National Weather Service (NWS), the National Park Service, the
D.C. Department of Energy and the Environment (DOEE), the National
Capital Planning Commission (NCPC), and representatives from
Arlington, Fairfax, and Prince George`s Counties, and the City of
Alexandria. The maps are being made available online thanks to
funding from D.C. DOEE and the City of Alexandria.

This same project also created tidal inundation maps covering the
same area. A subset of these tidal maps will be available on the
AHPS portal linked above. The full suite of tidal maps will be made
available on a separate site; links to all the web map locations
will be appended to an updated version of this statement closer to
the launch date.

For additional information on this new service, please visit:

If you have further questions, please contact:
Jason Elliott
National Weather Service Baltimore/Washington
Senior Service Hydrologist
Phone: 703-996-2234

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