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. For Region 4 (San Joaquin and Tulare) 90-110% of normal equates to 23.06” to 28.19”.  This region gained 1.08” in the month of January to reach a WY total of 6.80”.  This represents an increase of a mere 2.7%, compared to last month’s jump of 11.5%.

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If we consider the precipitation distribution for the state, we find that 73% of stations in Region 4 fall on the “dry” side of the distribution; this matches last month exactly.  The average % increase for January across the 26 reporting stations was 2.4%; for context, the median for the 114 reporting stations across the state was 2.62%.  Fiddletown - Dexter Ranch, just east of Sacramento, was the standout station for the second month in a row, but this time gaining only 6.13%, compared to December’s 20% increase.

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A Note about Core Water:

We are always exploring new ways to analyze the data. To better understand precipitation patterns, we examined accumulation percentages across all stations and divided them into quartiles—four equal groups that rank stations from driest (Q1) to wettest (Q4). Comparing “Core Water” (Regions 2/4/6) and “Non-Core Water” stations, we see a clear contrast: Core Water stations tend to be wetter, with most falling in Q3 or Q4 and only 3 of 61 in Q1. In contrast, nearly half of Non-Core Water stations are in Q1, highlighting a much drier distribution.