The pilot reported that, after the sky cleared, he departed the airport following another airplane as a flight of two. During the flight, they approached a ridge with no significant turbulence or issues. He added that they were suddenly in instrument meteorological conditions (IMC), and the lead airplane disappeared. He immediately changed course 10° to the left, and as he transitioned to instrument flying, the airplane encountered a downdraft. Shortly thereafter, the windscreen "filled with trees," which he estimated were less than a 100 ft away. He pitched the nose up to dissipate energy, and the airplane subsequently impacted trees and terrain. The airplane sustained substantial damage to both wings. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The nearest official weather reporting station, which was 16 miles southwest of the accident site, reported, about the time of the accident, 10 miles visibility, temperature 70°F, dew point 66°F, a broken layer at 2,700 ft, a second broken layer at 3,200 ft, and an overcast layer at 4,100 ft. Although these were marginal visual flight rules conditions, given the mountainous terrain, the pilot should have expected that the mountain peaks may become obscured, and with a 4° temperature/dew point spread that visibility conditions could change rapidly. The pilot recommended that he should have flown his original flight plan, which was at a lower altitude so that he could have avoided unexpected and unpredicted winds and entering IMC.