Flooding associated with the spring breakup of ice on Alaska's rivers is an annual event. The severity of flooding varies from year-to-year depending on such variables as river ice thickness, snow water equivalent of the winter snowpack, spring-time temperatures, and local river morphology. In anticipation of flooding due to ice jams and/or spring snowmelt runoff, the National Weather Service (NWS) Alaska Region has developed a close partnership with the state of Alaska to monitor ice and river conditions along several major rivers for the duration of the breakup cycle. Due to the remote nature of the state, lack of a dense observational network, and uncertainty of breakup flooding, the NWS relies heavily on aerial observations to assist with the forecasting of breakup flooding. The aircraft supported River Watch program was established in order to improve the NWS's ability to provide accurate and timely hydrologic Warnings for flooding in response to river ice breakup.
The following talk will discuss the hydrometeorological variables that led to the extraordinary flooding on the Yukon River in May 2009. The background and benefits of the River Watch Program will also be discussed.