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Latitude: 38.92º N | Longitude: 119.19º W | Elevation: 4420 Feet | |||
Location: Lyon County in Nevada | Bulletin Group: Eastern Sierra | River Group: Eastern Sierra |
Issuance Time: | Apr 30 2025 at 8:07 AM PDT | Next Issuance: | May 01 2025 at 9:00 AM PDT |
Action/Monitor: 9.0 Feet | Minor Flood: 9.8 Feet | Moderate Flood: 11.0 Feet | Major Flood: 11.6 Feet |
Please Note: | Significant losses can occur in the Mason Valley upstream of the Mason stream gage. Increased forecast uncertainty exists in the long range forecast due to these unknown losses. |
Please Note: 1) Each individual timeseries plotted on the graphical river forecast can be toggled on and off by clicking the legend entry above. If the "Observed (Raw Data)" contains bad data and is toggled off, the plot will scale to the remaining timeseries. 2) At extremely low river flows, the "Observed (Raw Data)" may show readings below the lower end of the available rating table, while the "Observed (Simulated)" will only show values at the bottom of the rating table, creating a potential discrepancy between the two readings. |
Observed Data Credit | |
![]() | Raw streamflow data is provided by the US Geological Survey (USGS). |
Historical Stage/Flow Data |
|||
Water Year
|
Peak Discharge (cfs)
|
Stage (feet)
|
Date
|
Most Recent 5 Years | |||
2024* |
917 |
6.69 |
Jun 8, 2024 |
2023* |
3,810 |
11.64 |
Jun 8, 2023 |
2022* |
321 |
5.48 |
May 30, 2022 |
2021* |
316 |
5.48 |
May 11, 2021 |
2020* |
335 |
5.62 |
Oct 8, 2019 |
Historical High Stage/Flow Events (Period of Record - April 1974 to Present)** - Ranked by Flow | |||
1997* |
3,900*** |
12.72 |
Jan 04, 1997 |
2023* |
3,810 |
11.64 |
Jun 8, 2023 |
2017* |
2,910 |
10.94 |
Jun 24, 2017 |
1995* |
2,980**** |
11.57 |
Jul 11, 1995 |
1983* |
2,790*** |
11.31 |
Jun 19, 1983 |
2011* |
2,420 |
10.77 |
Jul 01, 2011 |
* Discharge affected by regulation or diversion. | |||
** Break in data between Oct 1984 and Sept 2010. | |||
*** Prior to Sep 30, 1984 - gage location 0.1 mile downstream at different datum. | |||
**** Estimated using other gages and MASN2 rating #5.1 |
Location Photographs | ||
ESRI™ Locator Map |
Flood Impacts | |
13.0 Feet | Near record flooding in the Mason Valley-Yerington area. Significant flooding of homes and businesses in Yerington possible if breaches develop and the river spreads east. Extensive flooding of agricultural lands likely. Many primary and secondary roads flooded. |
12.5 Feet | Major flooding in the Mason Valley-Yerington area. Extensive flooding of farm and pasture lands. Many roads flooded. Some portions of Yerington flooded if breaches develop and the river spreads east. |
12.0 Feet | Major flooding in the Mason Valley-Yerington area. Some portions of Yerington flood if breaches develop and the river spreads east. Many roads flood. Extensive flooding of farmland and pasture near the river flood. |
11.6 Feet | Major flooding of lowlands throughout the Mason Valley-Yerington area. Structures adjacent to river in floodplain may be damage if not protected. Mason Valley Widlife Management area likely inaccessible. Flooding of many secondary and some primary roads occurs. |
11.3 Feet | Moderate flooding of lowlands to farm and pasture lands throughout the Mason Valley-Yerington area. Some low structures adjacent to river begin to flood. Several secondary and some primary roads flood. Exceeds flood peak of June 2017. |
11.0 Feet | Moderate flooding of lowlands, pasture and farmland adjacent to river throughout Mason Valley-Yerington area. Several rural and some secondary public roads flood. Yards and basements of lowest homes adjacent to the river in Mason and Yerington begin flooding. Preventative sandbagging is necessary. Possible damage to irrigation structures and levees Similar to June 24, 2017 peak, and slightly higher than July 1, 2011 peak. |
10.8 Feet | Minor flooding of lowlands...pasture and farmland adjacent to the river throughout the Mason Valley-Yerington area. Some rural roads flood. Preventative sandbagging of low structures in Mason and Yerington may be necessary as river rises, but limited flooding occurs. Some minor flooding of basements and yards in Mason. Similar level to floods of July 1 2011. |
10.5 Feet | Minor flooding of lowlands, pasture, farmland and some rural roads in Mason Valley. Preventative sandbagging of lowest homes in Mason and Yerington should be done as river rises, but limited flooding occurs. There may be some minor flooding of yards and basements in Mason. |
10.3 Feet | Minor flooding of lowlands,pasture and farmland in Mason Valley-Yerington area. Preventative sandbagging of lowest homes and businesses adjacent to river should begin if further rises are possible. Some flooding of rural roads, likely including Miller Lane. |
10.0 Feet | Minor flooding of lowlands, pasture, cropland and some rural roads throughout the Mason Valley/Yerington area. No flooding of structures. |
9.8 Feet | Flood Stage, Minor lowland flooding begins throughout Mason Valley-Yerington area, with some inundation of lowlands and rural roads. |
9.0 Feet | Monitor Stage, near bank full conditions. No flooding in the Mason Valley-Yerington area. |
Official 7 Day National Weather Service Forecast (NVZ001) |
Today: Sunny. Highs 66 to 76. Light winds becoming north around 10 mph in the afternoon. Tonight: Clear. Lows 42 to 52. Northwest winds 10 to 15 mph. Friday: Mostly sunny. Slight chance of showers in the afternoon. Highs 73 to 83. Light winds becoming southeast around 10 mph in the afternoon. Friday Night: Mostly cloudy. Chance of showers and thunderstorms in the evening, then chance of showers after midnight. Lows 45 to 55. West winds 10 to 15 mph. Saturday: Chance of showers in the morning, then showers and slight chance of thunderstorms in the afternoon. Highs 57 to 67. Light winds becoming west around 10 mph in the afternoon. Saturday Night: Showers likely and chance of thunderstorms in the evening, then showers and heavy snow showers likely after midnight. Lows 40 to 45. Sunday: Breezy. Showers likely in the morning, then chance of showers with pockets of snow showers and thunderstorms likely in the afternoon. Highs 48 to 58. Sunday Night and Monday: Mostly cloudy with a chance of showers. Lows 38 to 48. Highs 57 to 67. Monday Night and Tuesday: Partly cloudy with a slight chance of showers. Lows 39 to 49. Highs 64 to 74. Tuesday Night: Partly cloudy in the evening then becoming clear. Lows 43 to 53. Wednesday: Sunny. Highs 68 to 78. |
Product Disclaimer |
This river graphic is not intended to serve as a substitute for official flood watches, warnings, advisories, or statements issued by the NWS Reno Weather Forecast Office. Observations are preliminary and subject to change. River levels identified as "forecast" should be consistent with those contained in official NWS products. River levels identified as "guidance" have significant uncertainty due to future weather or reservoir regulation and are provided for planning purposes only. |