Modeling Study of Serve Downslope Winds during the Grassland Fire of Marshall, Colorado

The Front Range Mountains and Foothills regions of Colorado are no stranger to downslope winds and often experience multiple severe wind events during a typical season, November through March. On occasion, the severe downslope winds can be greater than 100 mph, causing damage to infrastructure and communities in the area. On December 30, 2021, a worst-case scenario was realized when a grassland fire was exacerbated due to the severe downslope winds. This fire, named as Marshall Fire, became the costliest wildfire in Colorado history (>$2 Billion) and occurred outside of the typical fire season. In this study, we applied the Weather Research and Forecasting model (WRF-ARW) to model the severe downslope winds that caused the rapid spread of the Marshall Fire. The WRF simulation was configured with three nested domains at 15, 3, and 0.6 km resolution, respectively. The simulation period covered the severe downslope winds for the fire duration from December 30, 00 UTC to December 31, 23 UTC 2021. Preliminary modeling results indicate that the WRF model basically captured the downslope wind event, though the timing and duration of the modeled peak winds show significant discrepancies with the station observations, representing a big challenge in accurately modeling the downslope winds in the region. Further sensitivity WRF simulations and analysis will be carried out to better understand the causes of discrepancy between the modeled and observed downslope winds during this extreme event.