Which of the following sets of meteorological conditions is indicative of a stable atmosphere?

1. Stratiform clouds, continuous precipitation, smooth air, and fair-to-poor visibility.
2. Cumuliform clouds, showery precipitation, turbulent air, and good visibility.
3. Clear skies, strong gusty winds, rapid temperature drops, and severe wind shear.
4. Towering cumulonimbus clouds, heavy rain, lightning, and microbursts.