snowpack · United States
Sierra Nevada (Phillips Station), California
1 April snow water equivalent
Modelled demonstration series · not observed data
California's water year is a bet that winter snow will melt slowly enough to carry the state through a rainless summer. The variance on this chart is the real story: enormous swings between years, with the wet years less able to compensate because more of their precipitation now falls as rain and leaves immediately.
75 years, modelled
Same reading, two normals
| Normal | Mean | σ | Pct | Return |
|---|---|---|---|---|
| 1951–1980 | 480 mm | −1.90σ | 3rd | 1 in 35 years |
| 1991–2020 | 423 mm | −1.38σ | 8th | 1 in 12 years |
Today would be the lowest value in the entire 75-year modelled series. Past the series' standing low of 128 mm (2012). Nothing about the reading changes between rows — only the yardstick.
The season here
1 April is the traditional date for measuring peak snowpack in California — it is the state's largest reservoir and it is made of snow.
Where this series comes from
MODELLED SERIES — not observed. Parameters set from published Sierra Nevada 1 April snow-water-equivalent climatology, which is genuinely extremely variable year to year; lognormal transform applied. The 75 annual values are synthesised by the seeded generator. Population is a rounded state water-user estimate.
Every number on this page comes from a modelled series: 75 annual values synthesised by a seeded generator from published climatological parameters for Sierra Nevada (Phillips Station), California. It shows how anomaly reasoning works. It is not a measurement and must not be cited as one.
How to read σ
σ counts standard deviations from this place's own normal. The sigma guide · return periods.
More snowpack stations
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