Bulletin: Extreme Ice Storm Possible

Below, I posted about my surprise pertaining to the lack of an ice storm warning in parts of South Dakota and north central Nebraska. Increasingly, it appears that concern is well-founded. As of 6:50p Central, there still is no ice storm or freezing rain warning.

The Sperry-Piltz Ice Accumulation Index (power outage index), an extremely useful, well-validated, tool for gauging the severity of ice storm damage to the electric grid has reached its (rare) highest value. The latest (via Twitter) is below:

Now, consider these SPIA values across a map of electrical transmission lines (the type you see on tall towers).

When several of these lines come down, power outages can be both widespread and prolonged. Plus, wet snow from the blizzard -- along with the forecasted extreme wind gusts -- may cause outages to the northwest of the colored areas on the SPIA. With transmission lines, can be much larger than the geographic location of the line damage.

Here are the impacts of the damage corresponding to SPIA values:

Note the phrase "shelters needed" and outages longer than five days.

While this is, generally, a sparsely populated area, if you or relatives live there, here are things to be thinking about:

• If you wish to make a move do it tonight before the storm arrives.
• If you have a baby or infant, infirm relative or someone who is dependent on electricity for medical assistance, consider evacuating now. 
• Thinking about staying? Make sure you are able to live independently for two weeks. 
• At minimum, fill your fuel tank, charge devices, etc. Turn off your phone and computer except when you absolutely need them. You may have to make that charge last a very long time. 

This storm is very roughly a 50-year event. So, don't judge this as a typical winter storm. It is a powerful, rare event.