The Impact of Snowmelt Timing on the Predictability of the Early Wildfire Season in Alaska

Wildfires occur each summer in the boreal forests of Alaska, with increasing frequency of extreme years (i.e. area burned exceeding 2 million acres) in recent decades. Forecasting the length and severity of the Alaska fire season is important for fire management planning, which begins during the late winter months each year. The start and magnitude of the early fire season in April-May is linked to the timing of the spring snowmelt onset. This study evaluates snow melt dates in Alaska from the ERA5 reanalysis over 1979-present using the Predictive Service Areas with the goal of developing subseasonal and seasonal (S2S) forecasts of the early fire season. Prior studies have shown that the timing of river ice breakup in Alaska, which is correlated with snowmelt, is tied to teleconnections such as the El Niño Southern Oscillation (ENSO) as well as storm tracks in the North Pacific Ocean. Preliminary results show that multiple ENSO teleconnection indices are significantly correlated with the snowoff date (when snow depth reaches 0mm) and the April-May Buildup Index (BUI) from the Canadian Fire Weather Index System in Interior Alaska. The correlations become weaker between snowoff date, ENSO and BUI by early June. Additional analysis is underway to determine the teleconnections and associated atmospheric mechanisms that become more prominent predictors of BUI later in the season.