Convectional — rising, warm air from beneath
- needs humidity to condense (reach dew point) and form clouds
- additional energy is provide when condensation begins
- Sierra Nevada summers (temps and moisture increase)
Frontal — when zones or "air masses" collide
- causes uplift and precipitation
- common "extratropical" storms across U.S in winter
- air
forced up by landform barriers
- namely mountains, islands, escarpments
- needs prevailing or other winds
- "rainshadow"
results on leeward side
