As the accumulation season comes to an end for North Cascade glaciers it is worth reviewing this winter and looking ahead with a forecast for glacier mass balance by the end of summer 2025. The winter of 2025 at NOAA’s Washington Cascade Mountain West Division 5 records indicate that this winter was below the declining trendline of total precipitation with a mean of 54.8 inches, down slightly from last year. Winter temperatures were again warm at 33.2^o F but close to the expected rising trend line average.

The mean April 1 snow water equivalent (swe) at the six North Cascade Snotel sites with a consistent long term record was 0.72 m. This is below the declining trend line and 31% below the long term average for the 1946-2025 period. This is above the 2024 value, but in the lowest quintile. Mount Baker ski area has reported 585 inches of snowfall through April 21, which is ~30% percentile. April 1 swe is the key date for asssessment for winter snowpack water resources. For glaciers the accumulation season typically continues until the end or April or early May. This year snowpack depth at Mount Baker Ski Area (1280 m) increased from 148 inches on April 1 to 164 inches on April 9 and then declining to 119 inches by May 1 (80% of normal). A similar pattern was seen at Stevens Pass-Grace Lake station (1460 m) with snowpack depth on April 1 of 107 inches, increasing to 114 inches by April 9 and decreasing to 82 inches by May 1. These stations are several hundred meters below glacier elevations. At Lyman Lake Snotel (1800 m) snowpack SWE which most closely matches the glacier elevations was 40.1 inches rising to 42.5 inches by April 11 and declining to 35.9 inches by May 1, ~60% of normal. At the Middle Fork Nooksack site (1520 m) snowpack was 44.8 inches SWE on April 1, rising to 49 inches by April 11 and declining to 46 inches on May 1, 67% of normal . This illustrates that at glacier elevations snowpack would have also increased in mid-April, before a slow decline in the latter part of the month. There were a number of atmospheric rivers that drove a higher snowline than usual as May starts, but also led to a rapid increase in snowpack above the snowline.

As the melt season begins, based on the above the winter snowpack on glaciers on May 1 are 70-80% of normal. Eric Gilbertson measured snowpack on the summit Colfax Peak at 17.3 ft (5.27 m) on April 18, 2025. This is a location that is to some extent wind scoured and would be less than the depth on the adjacent glacier, a normal year there is 8-9 m of snowpack at 2300-2800 m. On Eldorado Peak they found 25.3 feet on April 27, 2025. This is the depth expected for this location in a year with 75-80% of normal snowpack. It is a location that appears to balance enhanced deposition and scour. Weather conditions in the Pacific Northwest are forecast to have above average temperatures for the upcoming 90 day period. This combined with the below average snowpack on glaciers on May 1, will yield another year where ice thickness loss exceeds 1 m across the glaciers, as each of the last four years have. The average from 2014-2024 has been -1.41 m, which is a 1.5 thick slice of the glacier lost each year. The range expected this year is -1.2 m to -2.4 m. How much will depend on the specific weather and the frequency and intensity of heat waves.