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Routine Forecasts coming to the Tidal Potomac and
Washington Channel in Washington, DC

Beginning January 15, 2013, the National Weather Service plans to begin providing routine daily forecasts of tidal heights on the uppermost portion of the Tidal Potomac River, and the adjacent Washington Channel; both in Washington, DC.

Specifically, the gauge locations where new forecast services will be provided are:
* Tidal Potomac River at Wisconsin Avenue / Georgetown
* Washington Channel at SW Waterfront, Washington, DC

The water level forecasts provided may not fully account for the effects of wind-driven water or surge, especially in major events.

The National Weather Service will continue to utilize existing procedures for providing watch, warning, and advisory services to this area through the Coastal Flood suite of products. It is important to note that in wind-driven events, because of the limitation noted above – and because tidal flooding is not limited to these gauge locations – the NWS may issue coastal flood watch, warning, or advisory bulletins even though the displayed forecast remains below the established threshold.

The advisory/warning thresholds for these sites are:
Potomac River at Wisconsin Avenue/ Georgetown (DC)
Washington Channel at SW Waterfront (DC)
Action Stage
5.5 feet (WMLW)*
3.7 feet (MLLW)*
Minor Flood Level
(coastal flood advisory)
6.0 feet (WMLW)*
4.2 feet (MLLW)*
Moderate Flood Level
(coastal flood watch/warning)
7.0 feet (WMLW)*
5.3 feet (MLLW)*
Major Flood Level
10.0 feet (WMLW)*
7.0 feet (MLLW)*

*WMLW and MLLW are mean low water tidal datums. These tidal datums are utilized so that gauge values indicate the height above a long-term average low tide. Astronomical tide predictions are routinely referenced to MLLW. To convert to true NAVD88 elevation, subtract 1.25 from the Wisconsin Avenue value and 1.40 from the SW Waterfront value.

Forecast information may be viewed by choosing the Rivers and Lakes link on our website. To directly view forecasts for these two locations, use the two links below.

Potomac River at Wisconsin Avenue/Georgetown
Washington Channel at SW Waterfront

National Weather Service
Weather Forecast Office Baltimore/Washington
43858 Weather Service Rd.
Sterling, VA 20166
Phone: (703) 996-2200
Page last modified: Jan 10, 2013 10:25 PM EST
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