Big storms around the holidays have left snowpack and reservoir levels in good shape throughout the West, as Oregon’s snow level was 166% of normal and California’s was above average as of Monday, Jan. 6. La Nina atmospheric conditions, which favor colder northern systems, combined with a parade of atmospheric-river storms in November and December to leave a deep layer of snow throughout much of the region. Snowpack levels are above their 30-year averages in Oregon (166%), Nevada (131%), Idaho (119% south of the Salmon River), Washington (115%) and California (110%), according to the Natural Resources Conservation Service’s National Water and Climate Center. … The Colorado River Basin has recorded near-normal rainfall and snowfall this season, although Arizona and southeastern California are severely lagging.