The CAP forecast is valid for the state of California. However, we can estimate regional precipitation forecasts by applying the statewide forecast (90-110% of normal) to the regional precipitation averages.

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Precise regional forecast ranges and precipitation totals will be available in next month's report when we confirm which National Weather Service stations are actively reporting. Regional and statewide averages depend on the availability of NWS data. (See the section below for more information on observations.)

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We are strategically deploying additional stations to enhance our regional forecast precision. These stations are currently gathering data to build a strong foundation of insights, allowing us to fine-tune forecasts in the future. Until then, these estimates are intended to give you an idea of how the state-wide forecast may present in your particular region.

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A note about observation timing: 

In order to evaluate our forecast objectively, we utilize surface station measurements from the National Weather Service (NWS) Cooperative Observer network. Because of our reliance on external observations, it is important to note:

• Observations must be collected, submitted (electronically or by mail), quality controlled, and uploaded to NWS databases. This process can take several weeks and so the data in each monthly report will reflect the NWS precipitation numbers from the previous month (e.g. the monthly update sent the first week of December will include precipitation amounts through Oct 31).
• The stations available from month-to-month and year-to-year can change over time. While there is a “true” average precipitation amount for the state and for each region, the average that we provide is based on the available stations at the time of the report so that the observed precipitation totals can be compared with the average for those stations. As such, there may be slight fluctuations in the state and regional averages based on the station availability.
• We have worked hard to create a verification system that adjusts to these challenges in station availability. In a perfect world, each deployed NWS station would be consistently available; while this is not the case, there is room for improvement and your voice matters! Contact your local NWS office to remind them that data matters to you and your operations are impacted in its absence! https://www.weather.gov/media/nws/wcm-soo.pdf