LAUSR

We utilized a macroscale hydrology model in conjunction with an atmospheric river (AR) catalog to evaluate AR‐affected snow accumulation in the Upper Colorado River basin (UCRB) headwaters for water years 1951–2015. We find that there are on average 11.4 days during which AR‐originating snow accumulates in the UCRB each year, yielding 5.75 km3 of snow water equivalent (SWE). This AR‐originating SWE accounts for 30.8% of average annual peak SWE in the basin. Most of the ARs that reach the UCRB first intercept the Sierra Nevada region of California; 84% of days affected by ARs in the UCRB are also AR‐affected days in the Sierra Nevada. The pathways of the ARs reaching the UCRB do not have a great effect on snow accumulation, however ARs that first pass through the Sierra Nevada generally produce greater snow accumulations there than in the UCRB.