Overview
Seventeen balloons launched from various locations around the Napa Valley for local sightseeing flights. According to statements from pilots, passengers, and ground witnesses, while the balloons were in normal drifting flight, a microburst-like condition suddenly occurred which affected all of the balloons.
Weather Conditions
The weather phenomena encountered included strong gusting surface and aloft winds in addition to severe down drafts. The balloons were rapidly forced toward the ground as their ground speed increased radically. Pilots of several balloons reported that the shapes of their balloon envelopes were severely distorted by the sudden movement of the airmass.
Forced Landings
Eight of the 17 balloons attempted forced landings. Four of these balloons successfully landed. The other four balloons collided with obstructions and the ground during the attempted landings.
Additional Context
At the time of the incident, a large thunderstorm was reported 30 miles to the north.