National Weather Service United States Department of Commerce

Northern Tier Snow and Heavy Rain in the South; Blizzard Conditions in Alaska

A storm system originating from the Pacific Northwest will spread snow from the Upper Midwest to the Northeast into Tuesday. Locally heavy rain will be possible Tuesday in the Deep South. In Alaska, a storm will rapidly strengthen over the Bering Sea Monday where it will sweep strong winds and heavy snow across the state through midweek. Localized Blizzard conditions are forecast around Bethel. Read More >

Slide 11

A Tornado and an Overpass - What is Reality?

This topic, of course, begs the question: When it comes to a tornadic circulation interacting with an overpass - What is reality? This is an extremely difficult question to answer because it depends on many factors including (but not limited to):

  1. the strength of the tornado circulation,
  2. the tornado's "angle of attack" on the overpass,
  3. the overpass location relative to the path of the center of the tornado circulation,
  4. the construction of the overpass (particularly underneath), and
  5. the amount and type of debris that has been entrained into the circulation.

To our knowledge, this topic has never been studied scientifically. There have been no modeling studies done regarding the interaction of tornadic winds and an overpass. In the absence of careful scientific and engineering research into this question, no definitive recommendations can be made. There are some widespread misconceptions about this topic, however. These misconceptions are illustrated on the next few slides.

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