Hydrologic Outlook

ESFAFC BREAKUP OUTLOOK IS NOW IN A GRAPHICAL FORMAT: The graphical Alaska Spring Breakup Outlook products are posted to the Alaska-Pacific River Forecast Center website at: www.weather.gov/aprfc/breakupProducts A direct link to the latest graphical product is: www.weather.gov/media/aprfc/BreakupProducts/ESFAK_ACR_20260501.pdf UPDATES FROM THE PREVIOUS SPRING BREAKUP OUTLOOK: This Breakup Outlook continues to be refined to include more detailed flood potential and breakup timing information, including graphics and tables with community-specific flood risk and forecast breakup dates. Snowpack and ice conditions remain largely unchanged from the previous outlook, other than noticeable melt-off of snowpack in lower elevations of the Kuskokwim Delta and Tanana Valley. While not in full-swing, breakup began with the Kuskokwim at Nikolai on April 25. The most notable change is in the spring temperature outlook, which now favors near-normal to below normal temperatures through the first half of May. This is a change from the outlook a week ago, which favored above normal temperatures through early May. This trend could delay breakup across the state an extra day or two and is helping maintain ice cover and slow melt out. Climate models do continue to indicate above normal temperatures the second half of May. This rapid transition could increase the likelihood of a dynamic breakup, but timing will be critical. There is a good chance that widespread breakup will occur before the rapid warmup sets in. Overall, this combination continues to increase the likelihood of a more dynamic breakup. STATEWIDE FLOOD POTENTIAL OVERVIEW: The breakup flooding potential is above average across parts of mainland Alaska. In the Interior, the primary areas of concern are the upper Yukon and lower Tanana Rivers, along with the middle Kuskokwim River near Crooked Creek and Aniak/Kalskag. Portions of the middle and lower Yukon, lower Kuskokwim, and the North Slope also face an elevated risk. This increased threat is driven by a combination of above-average snowpack, average to above-average ice thickness, high river levels at freeze-up, rough ice or freeze-up ice jams reported in several Interior locations, and the delayed snowmelt from below-average April temperatures. In contrast, the Koyukuk, Kobuk, and upper Kuskokwim rivers, as well as rivers across Southcentral Alaska, have a lower breakup flood threat due to below- average snowpack. Communities are encouraged to review their flood response plans and preparedness actions in advance of breakup. Beyond main river ice effects during breakup, snowmelt flooding in small channels and ponding on frozen ground during warm days is possible. Ice may block these channels, causing rapid rises, strong currents, and localized flooding. Use caution when traveling off main rivers and stay aware of recent weather and river conditions. ADDITIONAL DETAILS: The Alaska-Pacific River Forecast Center has updated the format of its breakup outlook and summary products. The new format has moved to a graphical presentation, away from the historically text-based product. The graphical Alaska Spring Breakup Outlook products are posted to the Alaska-Pacific River Forecast Center website at: www.weather.gov/aprfc/breakupProducts