Updating annual state- and county-level forest inventory estimates with data assimilation and FIA data

•We propose a data assimilation procedure for updating estimates with USFS FIA data.•This procedure incorporates the design-based and model-based inferences.•Updated estimates are comparable with estimates requiring 5+ years pooled FIA data.•This procedure is 100% compatible with the FIA database that is publicly available.•This procedure is unbiased and efficient, suitable for official reporting instruments.