Web Portal Changes: The Advanced Hydrologic Prediction Service (AHPS) hosted at https://water.weather.gov will be replaced by the National Water Prediction Service (NWPS), with a target of March 2024. Existing AHPS content and features will be preserved and expanded within NWPS.

Experimental National Water Center Products: Flood Inundation Mapping services are now available for 10% of the U.S. population. Please visit https://www.weather.gov/owp/operations for more information. The National Hydrologic Discussion, Area Hydrologic Discussion, Flood Hazard Outlook, and real-time geospatial services depicting River Forecast Center and National Water Model forecasts, continue to be accessible via the URL above, as described in the StoryMap here.

Weather Forecast Office (Baltimore/Washington) Sterling, VA

Middle Atlantic River Forecast Center

Hydrograph

River at a Glance

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Probability Information Weekly Chance of Exceeding Levels Chance of Exceeding Levels During Entire Period Short-term Probabilistic Guidance (Experimental)

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Printable Image About this graph Tabular Data (UTC) Tabular Data (EDT) Datum: Not Available Metadata

NOTE: Forecasts for the Potomac River near Washington DC (Little Falls) are issued routinely year-round.

Default Hydrograph Scale to Flood Categories   Return to Area Map

Upstream Gauge

Downstream Gauge

Flood Categories (in feet) Major Flood Stage: 14 Moderate Flood Stage: 12 Flood Stage: 10 Action Stage: 5 Low Stage (in feet): -9999 Historic Crests (1) 28.10 ft on 03/19/1936 (2) 26.88 ft on 10/17/1942 (3) 23.30 ft on 04/28/1937 (4) 22.03 ft on 06/24/1972 (5) 19.29 ft on 01/21/1996 Show More Historic Crests (P): Preliminary values subject to further review. Recent Crests (1) 10.16 ft on 05/09/2022 (P) (2) 11.56 ft on 12/17/2018 (3) 11.01 ft on 09/29/2018 (4) 10.85 ft on 09/11/2018 (5) 12.38 ft on 06/05/2018 Show More Recent Crests (P): Preliminary values subject to further review. Low Water Records Currently none available. For more information on your flood risk go to www.floodsmart.gov. Show FEMA's National Flood Hazard Layers FEMA's National Flood Hazard Layers not showing? Why aren't the FEMA National Flood Hazard Layers showing on the ESRI Map? Possible reasons: There are no FEMA National Flood Hazard Layers for the location which you are viewing on ESRI Maps. The FEMA Web Mapping Service (WMS) is down. Note: Your zoom level may have changed. ESRI's zoom levels must be between 14 and 16 to show National Flood Hazard layers.

Zoom Level:14 Legend FEMA Layer Gauge Location Disclaimer Latitude/Longitude Disclaimer: The gauge location shown in the above map is the approximate location based on the latitude/longitude coordinates provided to the NWS by the gauge owner.

Flood Impacts & Photos

If you notice any errors in the below information, please contact our Webmaster
17	Water overflows the overlooks at Great Falls National Park and approaches the lower level of the visitors center. Most of the C&O Canal towpath downstream of Pennyfield is flooded. There is approximately a foot of water in the clubhouse on Sycamore Island.
16	Water reaches the clubhouse on Sycamore Island.
15	Most of the C&O Canal towpath from Pennyfield downstream is flooded.
14	Significant portions of the C&O Canal towpath are flooded. The Blockhouse Point Park is flooded. Water reaches the retaining wall at Overlook 1 at Great Falls National Park but does not overtop it.
12	The C&O Canal overflows at the Great Falls Tavern. Water covers the towpath in many areas.
11.5	Water covers the towpath in multiple spots between the Washington Aqueduct Dam and Pennyfield Lock, mileposts 15 to 19 on the C&O Canal.
11	Water covers the towpath between Swains Lock and Pennyfield Lock, mileposts 17 to 19 on the C&O Canal.
10	Water begins to overflow the banks into low lying areas on the Maryland side of the river near Little Falls. Water begins to enter the canoe shed at Sycamore Island.
9	Several trails on both sides of the river between Great Falls and the Chain Bridge are flooded and will be closed.
7	Upper portions of the River Trail at Great Falls National Park begin to flood and will be closed.
5.5	Water reaches the top of the ferry landing for Sycamore Island. Ferry service to the island will likely be suspended.
5	Portions of the Potomac Heritage Trail begin to flood. Water begins to affect portions of the Billy Goat Trail between Great Falls and Carderock. These trails will be closed.
4.5	The river reaches danger level for boaters, as defined by the State of Maryland. Conditions for boating will be extremely hazardous.
3.5	The river reaches caution level for boaters, as defined by the State of Maryland. Fast moving water and changing currents will be experienced.

About This Location

Latitude: 38.949722° N, Longitude: 77.127778° W, Horizontal Datum: NAD83/WGS84 River Stage Reference Frame Gauge Height Flood Stage Uses NWS stage 0 ft 10 ft Interpreting hydrographs and NWS watch, warnings, and forecasts, and inundation maps Vertical Datum Elevation (gauge height = 0) Elevation (gauge height = flood stage) Elevation information source NAVD88 Not Available Not Available Survey grade GPS equipment, FEMA flood plain maps, newer USGS topographic maps NGVD 29 37.95 ft 47.95 ft Older USGS topographic maps, NGVD29 benchmarks MSL Not Available Not Available Older USGS topographic maps, MSL benchmarks Other Not Available Not Available   Current/Historical Observations: U.S. Geological Survey (USGS) Data and Site Info for Washington DC (Little Falls)

Additional Information

Potential River Levels Used to Estimate the Chance of Flooding and the Range of Possible River Levels 10 Day (HEFS) 7 Day (NAEFS) 7 Day (GEFS) Note: Use the official hydrograph at the top of this web page for river levels within the next 72 hours. Click individual graphics to enlarge.

Resources

Hydrologic Resources Text Products Past Precipitation Forecast Precipitation River Forecast Centers River Stage Summary Automated Flood Warning Systems Inundation Mapping Locations

Additional Resources Area Hydrographs NWS Precipitation and River Forecasting AHPS Iframes for Developers Mobile iNWS for emergency management Snow Information Ensemble River Forecasts Hourly Precipitation

Collaborative Agencies The National Weather Service prepares its forecasts and other services in collaboration with agencies like the US Geological Survey, US Bureau of Reclamation, US Army Corps of Engineers, Natural Resource Conservation Service, National Park Service, ALERT Users Group, Bureau of Indian Affairs, and many state and local emergency managers across the country. For details, please click here. NWS Information National Weather Service (Baltimore/Washington) Sterling Weather Forecast Office 43858 Weather Service Rd. Sterling, VA 20166 (571) 888-3500 Ask Questions/Webmaster Page last modified: 2-Nov-2020 7:30 PM Disclaimer Credits Glossary Privacy Policy About Us Career Opportunities