Analysis of the Alaska snowpack indicates below average conditions in most of western and northern Alaska. Below average conditions were also indicated for southeast Alaska. See figure below.
The majority of our snow fell between October and early January. Temperatures generally were above average in November and February and near average in December. January was generally below average in temperature. The relatively warm temperatures and early snowfall that provided insulation caused below average ice growth on most interior rivers and less freezing of the ground. Based on a few available measurements, river ice is 50 to 75 percent of the average thickness.
The forecasted temperature regime combined with below average snowpack, ice thickness, and ground freezing should cause a low to average threat of breakup flooding for villages along the Tanana, Yukon, Koyukuk, Kuskokwim, and other rivers in interior Alaska. Ice breakup flood potential for southcentral and southeast Alaska is low, since much of the low elevation snowpack has already melted due to recent warm temperatures. The potential for small stream and urban flooding resulting from drainage problems and icing is rated as low to average. Weather conditions during late March through mid May, such as heavy snowfall or a long cold spell, can significantly alter the present river flood potential outlook.
The flood potential is rated as low, average, or high, which means:
Low..communities that flood nearly every year may experience minor flooding of low lying areas.
Average..communities prone to ice jam floods are likely to flood, other locations are less likely to flood.
High..several communities are very likely to flood, and the extent of flooding may be substantial
Updates to this spring breakup outlook will be done weekly and can be found on our home page at akrfc.arh.noaa.gov