The April precipitation was over 200% of average from the Feather River down through the Merced. The largest departures from normal occurred in the Feather through the American River watersheds (see Figure 1). The 8-station index is currently at 7.74 inches, and ranks 13th wettest in the 106-year index record.
Figure 1 - April 2026 departure from normal precipitation estimated by CNRFC as of April 27th.
As expected, the impact on April-July runoff is most noticeable in the Feather, Yuba, and American watersheds. The table below compares the April-July median runoff projections from March 18th to April 26th. As you can see, the largest increases are in the watersheds where the April precipitation departures are the greatest.
Figure 2 - CNRFC median April-July runoff forecast comparisons
While these increases are nice to see, the April-July runoff forecasts are still much below normal for most of the area (Figure 3). A large reason for this is due to the unprecedented warm March accompanied by significant snowmelt. The additional SWE gains during April pale in comparison to the SWE losses experienced in March. California statewide snowpack is still extremely low - 22% of normal (Figure 4).
Figure 3 - April-July runoff percent of average forecasts as of April 27th.
Figure 4 - CA statewide snow water equivalent as of April 27th (courtesy of CA DWR).
One bright spot has been the water year runoff. For most locations, water year runoff projections are only slightly below or near normal. The warm storms that hit the region this winter coupled with the record breaking March temperatures resulted in more runoff than average during the December through March timeframe. This is evident in the Central Valley Index water year trend plot. The observed runoff (pink line) tracked above the average accumulation (blue dashed line) from late December through the first half of March. Currently, water year runoff is 106% of normal. As we work our way through the remainder of the spring, runoff is expected to be below normal due to the low snowpack, and the pink line will ultimately come in below the average accumulation line (91% of average).
Figure 5 - Central Valley index water year runoff forecast trend plot
The Climate Prediction Center’s two to three week outlooks is indicating an above normal trend. For the 8-14 day period, CPC is indicating a 40-50% chance of above normal precipitation for much of the Central/Southern Sierra, and their 3-4 week outlook issued last Friday is also indicating a slight chance of above normal precipitation. While this may not amount to a significant amount of precipitation, every little bit helps to elevate baseflows during this below normal snowmelt period.
Figures 6 and 7 - Climate Prediction Center week 2 and week 3-4 precipitation outlooks
