Atmospheric River Bringing Heavy Rain to Southern California and Heavy Snow to the Sierra Nevadas

A strong atmospheric river will continue heavy rain over southern California through Friday. The heaviest rainfall is ongoing today in the Los Angeles Basin. Flash and urban flooding is possible. A prolonged heavy snowfall has begun over the Sierra Nevada Mountains and will continue through Friday. Travel will become increasingly difficult over the passes due to snow and strong winds. 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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Atmospheric River Bringing Heavy Rain to Southern California and Heavy Snow to the Sierra Nevadas

Convective Parameters - Helicity 0-3km