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 >

Automatically generated image showing areas of surface-1km vertical shear.

 

Thumbnail of an automatically generated image showing areas of surface-1km vertical shear. Thumbnail of an automatically generated image showing areas of surface-1km vertical shear. Thumbnail of an automatically generated image showing areas of surface-1km vertical shear.
Hour - 1 Hour - 2 Hour -3

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Shear (0-1km) 

Surface-1-km Vertical Shear is the difference between the surface wind and the wind at 1-km above ground level. These data are plotted as vectors with shear magnitudes contoured. 0-1-km shear magnitudes greater than 15-20 knots tend to favor supercell tornadoes.

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