National Weather Service United States Department of Commerce

Heavy Rain and Flash Flooding Concerns in California; Heavy Snow in the Sierra

An atmospheric river will bring heavy rainfall to lower elevations of California this week, and heavy snow to the Sierra Nevada mountains. Flash flooding, some of which may be locally considerable, will be a concern on the western foothills of the Sierra Nevada mountains through Tuesday. Landslides, rockfalls and mudslides are possible in the Southern California mountains. Read More >

 
 
 
 

The National Weather Service uses the following definitions when describing winter weather:

An advance statement that severe winter weather conditions are possible within the next day or two.

An urgent statement that severe winter weather conditions have begun or will begin within about 12 hours.

 Advisory

A statement that winter weather conditions are imminent or occurring. These conditions will cause significant inconvenience, and may become hazardous or life-threatening if safety tips are not followed.

 Heavy Snow

Snowfall which accumulates to a depth of at least 4 inches in 12 hours or 6 inches in 24 hours.

 Sleet

Pellets of ice composed of frozen or mostly frozen raindrops, or snowflakes which have melted and refrozen.

 Freezing Rain/Freezing Drizzle

Rain or drizzle which falls as liquid then freezes when it strikes the ground or other surface.

 Frost

The formation of thin ice crystals on the ground or other surfaces.

 Wind Chill

A cooling effect caused when wind blows across exposed skin.