National Weather Service United States Department of Commerce

Atmospheric River to Begin to Impact the Northwest U.S.; Gusty Winds in the Northeast U.S.

A strong atmospheric river moving into northern California later Tuesday will bring a threat for moderate to heavy rainfall and flooding, gusty to high winds, and mountain snows for parts of the Northwest U.S. through at least Wednesday. Gusty winds and isolated rain and snow showers will continue in the Northeast U.S. Tuesday behind a cold front. Read More >

Automatically generated image showing areas of storm relative helicity.

 

Thumbnail of an automatically generated image showing areas of storm relative helicity. Thumbnail of an automatically generated image showing areas of storm relative helicity. Thumbnail of an automatically generated image showing areas of storm relative helicity.
Hour - 1 Hour - 2 Hour -3

4 Panel Display | Animated Loop

Helicity (0-1 Km) 

This is the 0-1 km (approximately 0-3,000 Ft. AGL) storm relative helicity which is a measure of the amount of low level wind shear available for tornadogenesis. This is not a good indicator of supercell potential which is related more strongly to 0-6 KM vertical shear. Values greater than 100 m**2/s**2, do suggest an increased threat of tornadoes provided a supercell is present.  Larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells.

The arrows indicate the approximate right supercell storm motion using the Bunkers technique.

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