11. "' Stratocumulus Castellanus "'have stronger convective activity due to the presence of increasingly unstable air . 12. A few rumbles of thunder are possible in the unstable air mass near the Southeast Coast. 13. Such large aircraft can create unstable air in their wake because their wingtips throw off minitornadoes. 14. Thunderstorms are possible in eastern Washington and Oregon as the front pushes into more unstable air . 15. Rain cooled air plunging earthward, called downdrafts, accelerate in the unstable air mass that supports strong thunderstorms. 16. Additionally, " a strong low-level easterly flow which forced the moist unstable air up-slope on the hills. 17. Behind the storm, chilly, unstable air will be forced south over the Great Lakes and the Ohio Valley. 18. Soukhanov says, " but you'll find it on television, referring to boxes of very unstable air or hurricanes ." 19. Cool, unstable air will cover the Northeast as an unseasonably strong low-pressure area becomes nearly stationary over southeastern Canada. 20. They occur in highly unstable air and often have complex structures that include cirriform tops and multiple accessory clouds.