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 0-3 km storm relative helicity.


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Helicity (0-3 Km)

This is the 0-3 km (0-10,000 Ft. AGL) storm relative helicity which is a measure of the amount of wind shear available from the ground to roughly 700 MB. Values greater than 250 m**2/s**2 suggest an increased threat of tornadoes, but high values with this index do not necessarily suggest that the environment is supportive of supercell structures (look at 0-6 km shear). Larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells. Negative values suggest that anti-cylonic (left moving) supercells will dominate.

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

Convective Parameters - Helicity 0-3km