Abstract Nitrous acid (HONO) governs wintertime hydroxyl radical (OH) production, critically linking radical cycling, tropospheric oxidative capacity, and air pollution. During a mid‐latitude snowfall event, rapid HONO enrichment was observed alongside concurrent depletion of other pollutants. This unexpected phenomenon is attributed to heterogeneous reactions on fresh snow’s high surface area, an interpretation supported by HONO budget parameterization. In contrast, aged snowpack exhibited negligible production potential, contradicting prior snowpack source identifications. This divergence arises from snow aging processes that reduce surface area and alter chemical reactivity. These findings reveal previously unrecognized meteorology‐chemistry interactions, underscoring further investigation into these complex processes.