High Risk Of Flooding This Spring, With Heavy Snowpack & Ice Jams In Interior

 National Weather Service & NOAA 

Spring Breakup Outlook for Alaska 

March 13th, 2026

May, 2023 Moose Creek flood. (Photo, Country Journal archive)

Statewide Flood Potential Overview

The potential for spring ice breakup and snowmelt induced flooding is above average across a large portion of mainland Alaska. In the Interior, most of the Yukon River, Tanana River, and the lower Kuskokwim River are areas of primary concern. This heightened risk, common for Interior regions where breakup flooding is more frequent, is attributed to several factors: above-average snowpack, average to above-average river ice thickness, high freeze-up stage, and rough ice conditions or freeze-up ice jams reported across several interior locations. In contrast, the Koyukuk River basin and rivers across Southcentral Alaska face a lower breakup flood threat due to below-average snowpack.

This outlook is based on observed snowpack, ice thickness reports, and seasonal temperature outlooks. The term ‘normal’ is defined as being at or near the climatological average, which is typically defined over a 30-year period of record.

River Ice Observations

Interior Alaska experienced its coldest winter in roughly 30 to 50 years, resulting in generally above-average river ice thicknesses based on measurements collected from late February through early March. On the Tanana River at Nenana, early March ice thickness, where records extend back to 1989, was tied for the highest value observed for that time of year. In addition, many interior rivers experienced high freeze-up stage and jumbled ice conditions associated with freeze-up ice jams, particularly along the lower Yukon River and portions of the Kuskokwim River. These conditions can lead to an increased potential for ice jam flooding during spring breakup.

Cumulative Freezing Degree Days (FDD) are commonly used as a proxy for river ice thickness in Alaska, especially since sites with direct river ice observations are limited in number. This winter has been notably cold across much of the state. South of the Brooks Range, FDD totals are significantly above normal, generally ranging from 106% to 170% of the long-term average. In contrast, FDD totals north of the Brooks Range have remained near normal.

Snowpack

The March 1 snowpack analysis from the Natural Resources Conservation Service (NRCS), along with ERA5 snow water equivalent estimates, indicates a highly variable snowpack across Alaska. Snowpack is most pronounced across the Canadian Yukon and eastern Interior Alaska, including the Upper Yukon and Tanana River basins, where snowpack is approximately 130–150% of average. Above average snowpack is also present across the Yukon-Kuskokwim Delta and parts of the North Slope (110–150%). In contrast, the Koyukuk River basin and much of southwest Alaska, including the Upper Kuskokwim River basin, along with southcentral Alaska, have below-normal snowpack (50–90%).

Climate Outlook

Spring temperatures in April and May are the most critical factor in determining the severity of ice breakups. Dynamic breakups, which carry a higher risk of ice jam flooding, typically require cooler-than-normal temperatures in early April, followed by a rapid warm-up to summer-like temperatures in late April or early May.

Spring Breakup Outlook for Alaska Valid March 13, 2026

The current outlook, issued in February by NOAA’s Climate Prediction Center (CPC), suggests a colder-than-normal March and early April for Alaska. For the March-May period, the outlook is mixed:

• ●  Northwest Coast favor increased chances for above-normal temperatures,

• ●  Southcentral and Eastern Interior (Upper Yukon Basin included) favor below-normal

  temperatures,

• ●  Lower Yukon and Kuskokwim River basins tilt toward near normal temperatures.

  This temperature pattern could lead to delayed snow and ice melt through early Spring and increase the likelihood of dynamic breakup across the Upper and Middle Yukon River, as well as the Tanana River.

  However, long-lead climate guidance released in early March suggests a potential for above-normal temperatures across most of Alaska mid April through May, particularly across the central interior and southwest. If this temperature pattern holds, the chances for a dynamic breakup could decrease and reduce ice jam related flood risk across the Lower Yukon and Kuskokwim Rivers.

  The next update will be published April 10, 2026.