A balloon carrying an electric field meter and a standard meteorological radiosonde rose into a relatively small, isolated thunderstorm in central New Mexico on July 16, 1977. The electric field, E, versus altitude between 3200 m (surface) and 7000 m above sea level can be explained reasonably well by the following charge distribution: (1) a 130 m thick layer of positive charge just above the surface with a density of 1.7¿10-9C/m3; (2) a localized 1 C of positive charge moving downward on rain with a velocity of 8 m/s at a horizontal distance of 420 m from the balloon; (3) a 1-km thick 'layer' of negative charge between 4800 and 5800 m above sea level with a density of about -5¿10-9C/m3. This negative charge spanned a temperature range of about -2 to -5¿C. Between 7000 and 10,000 m above sea level, the balloon was near the edge of the cloud where E was low and principally horizontal. Above 10,000 m the balloon ascended into an anvil cloud that was apparently positively charged.