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 Denver/Boulder, CO

Missouri Basin River Forecast Center

Hydrograph

River at a Glance

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Printable Image About this graph Tabular Data (UTC) Tabular Data (MDT) Datum: NGVD29 Metadata

NOTE: Forecasts for the Saint Vrain Creek at Lyons are issued as needed during times of high water, but are not routinely available.

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Downstream Gauge

Flood Categories (in feet) Major Flood Stage: 10.5 Moderate Flood Stage: 9.5 Flood Stage: 8 Action Stage: 7.5 Low Stage (in feet): -9999 Historic Crests (1) 13.00 ft on 09/12/2013 (2) 7.53 ft on 06/01/2014 (3) 7.06 ft on 06/12/2015 (4) 6.19 ft on 06/13/2016 (5) 5.36 ft on 06/07/2021 (6) 5.24 ft on 06/18/2017 (7) 5.15 ft on 07/02/2019 (8) 4.39 ft on 05/28/2018 (9) 4.37 ft on 06/04/2020 (P): Preliminary values subject to further review. Recent Crests (1) 5.36 ft on 06/07/2021 (2) 4.37 ft on 06/04/2020 (3) 5.15 ft on 07/02/2019 (4) 4.39 ft on 05/28/2018 (5) 5.24 ft on 06/18/2017 (6) 6.19 ft on 06/13/2016 (7) 7.06 ft on 06/12/2015 (8) 7.53 ft on 06/01/2014 (9) 13.00 ft on 09/12/2013 (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:13 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

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12	This is an extreme, life threatening flood. Roads crossing the creek downstream through Longmont and all highways into Lyons will likely be flooded and impassable.
11	This is a major, life threatening flood. There is extensive flooding from Lyons downstream through Longmont impacting numerous roads and structures.
10.5	Houses and businesses along the creek from Lyons downstream through Longmont flood as do roads along and crossing Saint Vrain Creek.
10	A number of roads along and crossing Saint Vrain Creek in Lyons are impacted by flooding. Water overtops driveways and parking lots near Main Street in Longmont.
9.5	Flooding affects a significant area in Lyons with a number of houses along the creek impacted. Saint Vrain Creek floods low lying areas downstream in Longmont.
9	Several houses east of 2nd Avenue in Lyons flood.
8.5	Structures flood in low lying areas next to Saint Vrain Creek in Lyons. Lowland and meadow flooding occur along the creek downstream through western Longmont.
8	The creek rises to the base of structures and yards flood east of the 2nd Avenue bridge in Lyons.
7.5	There is lowland and meadow flooding in and downstream of Lyons.
Photos (1) Looking Upstream (2) Looking Downstream

About This Location

Latitude: 40.217900° N, Longitude: 105.260300° W, Horizontal Datum: NAD27 River Stage Reference Frame Gauge Height Flood Stage Uses NWS stage 0 ft 8 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 5289.14 5297.14 Older USGS topographic maps, NGVD29 benchmarks MSL Not Available Not Available Older USGS topographic maps, MSL benchmarks Other Not Available Not Available

Additional Information

Observations provided by the Colorado Division of Water Resources

Resources

Hydrologic Resources Text Products Past Precipitation Forecast Precipitation River Forecast Centers River Stage Summary NE/NC Colorado Graphical Forecasts Precipitation & Temperature Outlooks CoCoRaHS Precipitation Observation Maps HPRCC Climate Maps Cooperative Observer Monthly Precipitation Drought Monitor - Colorado CCC NIDIS Weekly Drought Summary Seasonal Drought Outlook Colorado Snow Maps & Graphs U.S. Snowfall Analysis Map National Snow Cover Analyses Probabilistic Winter Precipitation Guidance Turn Around Don't Drown

Additional Resources Area Hydrographs NWS Precipitation and River Forecasting AHPS Iframes for Developers Mobile iNWS for emergency management Colorado DWR Real-time Streamflow CWCB Drought, Flood & Water Supply Denver Water Reservoir Levels Fort Collins Stormwater Warning System NRCS SNOTEL & Snow Course MHFD ALERT Rainfall & Streamflow USBR Central CO Lakes & Reservoirs USGS Current Colorado Streamflow USGS WaterWatch Colorado Inundation Mapping Locations

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