Historic Severe Outbreak Forecasted To Affect 80 Million In Metros (More Tornadoes Today)

May 24, 2011; 11:51 AM ET

If you tried to draw a severe weather threat map over most of the population of the Eastern U.S., you couldn't do much better than this. One worry everyone seems to have this year (and for good reason in a Spring with record tornado deaths) is: Will my city be hit by a tornado? It seems to be happening a lot lately.*

As you can see from the map above, which shows cities in black, nearly every major metropolitan area in the heart (and east coast) of the country is under a severe thunderstorm threat today. I tabulated the major metropolitan centers only, and came up with a number of 70 million city folks who are in the Slight Risk area, with 11.5 million in the Moderate or High Risk areas (where tornadoes are most likely to occur).

Although storms could pop up any time now, the most severe will fire in Oklahoma mid-afternoon and spread eastward. Here's one computer forecast model's estimate of what the radar will look like late in the evening:

Mike Smith says "[The 45% chance of tornado] level is reached in a forecast only once every five to ten years." The widespread distribution of this potential outbreak, combined with the large number of people affected, makes a historic outbreak likely today. And tomorrow will have 23.7 million in the Slight and 5.7 million in at least a Moderate. That's a total of over 17 million people in a tornado threat during the two days! If there were ever a time that people in the city need to prepare, it's now.

Preparation is simple, as Henry said in his video today. Know where your evacuation area is where you'll be during the day and night, and know where your family should meet if a tornado strikes your city and cuts off roads.

*While the true cause of the unusually deadly Spring is undetermined, my opinion is that it is likely a combination of unusually strong tornadoes due to La Nina, and increasing population in these areas. These types of outbreaks have probably happened before (although it may have been more than 50 years), so it's likely not Climate Change.

Classic Plains Tornado Outbreak Ingredients
by Jonathan Erdman, Sr. Meteorologist
Updated: May 24, 2011 2:30 pm ET

Sadly, given the events in Joplin, Mo. and Minneapolis this past weekend, we are not through with severe weather this week. Not by a longshot. The ingredients are in place for a classic Plains tornado outbreak Tuesday. First, we have a screencast discussing how this setup compares to the infamous May 3, 1999 tornado outbreak. Then, we'll highlight the area of greatest risk, then step through why this is the case.