The Impact of Snowoff Timing on the Predictability of the 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 broadly linked to the timing of the spring snowmelt. This study evaluates snowoff dates in Alaska derived from the ERA5 reanalysis over 1959-present using the Predictive Service Areas with the ultimate 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 entering the northern Gulf of Alaska. The results show that ENSO teleconnection indices are significantly correlated with 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. Snowoff is not well correlated with historical wildfire activity or BUI beyond June, however it is correlated with teleconnections such as the Eastern Pacific - North Pacific that are linked with BUI and therefore make it a potential proxy for predicting climate conditions later in the season.