Height of base:

below 2000 m (6500 ft), even at ground, fog, mist (low-level clouds)

Description:

Grey, featureless;

Diffuse edges

Occurrence:

World-wide; most common in coastal and mountain areas

Made of:

water droplets

Precipitation:

None; possible light drizzle or graupel

Formation:

Slow lifting of large layer

Species:

Nebulosus, fractus

Varieties:

Opacus, translucidus, undulatus

How to distinguish from …

Cirrostratus (Cs)

Cs is higher and brighter; if translucidus, Cs forms halos or parahelia

Altostratus (As)

Hard to distinguish; As is higher than St; if translucidus sun appears less diffuse through St; sun has speckled appearance through As

Nimbostratus (Nb)

Nb has a ragged base and precipitation

Stratus opacus

(Morris, November 2006)

Stratus fractus opacus

(Morris, November 2006)

Stratus nebulosus translucidus

(Morris, January 2007)

Stratus nebulosus translucidus

Morris, March 07

Stratus with virga

Morris, May07

Orographic stratus opacus,

evaporation fog on lake

Hebgen Lake, Mo, July06