[1] Proximity balloon soundings for snow events with lightning and thunder during the period 1961 through 1990 reveal a less statically stable environment than similar nonthundering snow events. When thundersnow is present, a less stable environment (and in some cases subsequent upright convection) is found aloft in all of the thundering cases examined here; all of the events feature their most unstable parcel originating above a frontal inversion. In fact, only events in the cold air north of an extratropical cyclone are included in this study. Events with a lake effect or orographic enhancement are eliminated from the sample. The basic composite derived by averaging temperatures at an established interval reveals a nearly saturated lower atmosphere, below 0°C throughout its depth, with the frontal inversion present and its most unstable parcel occurring just above the top of the inversion. The feature-preserving composite approach of R. A. Brown (1993) better defines the frontal inversion bottom and top as well as the level and temperature of the most unstable parcel; these are the features in need of preservation, and a less statically stable environment emerges by doing so. Other salient features include the most unstable parcel originating some 30-50 mbar above the top of the frontal inversion and significant drying $100 mbar above the level of the most unstable parcel. The bulk sounding characteristics also favor the existence of lightning. The composite temperature at the level of the most unstable parcel is À8.7°C, which allows for enhanced amounts of supercooled water to enter any updraft that may form. The temperature of the most unstable parcel at its origin is also warmer than the charge reversal temperature; therefore convection of any appreciable depth will span that level. Moreover, the height of the composited À10°C level is 2959 m above ground level, which previous investigators have shown is sufficiently high to favor lightning production. Yet no convective available potential energy (CAPE) appears with either composite approach, which concurs with previous studies. While several of the composite members feature CAPE for elevated layers, the majority do not, suggesting that other processes (e.g., the release of symmetric instability), which are difficult to assess from a single sounding, tend to be at work.