Updated at 4pm: Extreme Weather in the Central Great Plains

We have two watches in effect as of 3:15. 

Blue is a watch for Kansas and southeast Colorado. It forecasts:

• A tornado or two.
• Wind gusts to 70 mph.
• Hail to 2.5" in diameter.

Yellow is a watch for Oklahoma and a bit of north central Texas. It forecasts:

• A few tornadoes.
• Wind gusts to 90 mph.
• Hail to 5" in diameter. 

Obviously, these are forecasts of extremely serious conditions. Go here and scroll down for safety recommendations that should be completed now. 

Tornado Watch for north and central Texas including the DFW Metroplex. 

Yellow is a watch for central and north Texas which forecasts:

• Tornadoes.
• Wind gusts to 80 mph.
• Hail to 5" in diameter.

As of 3:50pm, the regional radar shows severe thunderstorms in western Oklahoma and the beginnings of the derecho over southwest Kansas. It will begin moving southeast across the yellow watch area creating extreme winds and, likely, tornadoes. One of the reliable models is forecasting a peak gust of 111 mph with the derecho. Power failures are likely. 

Update: Note the new thunderstorms developing west of Waco.

I will update again around 5:30pm. 

For more, follow me on Twitter @usweatherexpert. 

If you would like to learn how the tornado and derecho warning system works, go here. 

Finally, I'm repeating the safety suggestions we have written about several times today:

• Call friends and relatives to make sure they are aware of the threat, especially if they live in a mobile home. 
• Make sure you have at least three ways of receiving storm warnings. 
• If you live in a mobile home, you may wish to move spend time with a friend or relative when a tornado or severe thunderstorm watch is issued. 
• Ask yourself what you would need if you were without electricity for five days. In some areas it will be longer, but five days is a good planning target.
• If you have a chain saw, fill it with fuel.
• Fill your generator with fuel and, if portable, make sure it is located a long way from air intakes such as your air conditioner. See instructions that came with the generator. 
• Check your tornado shelter. Make sure it has a couple of bottles of water and, if appropriate, diapers.
• Any essential foods or medicines should be taken care of immediately, well before the storms arrive. 
• Have all of your devices charged but disconnect when you see the first lightning or hear the first thunder.
• Keep the kids in close communication. 
• Bring in lawn furniture, trampolines or anything else that can blow away. 
• Put the car in the garage. 

I'll update in the mid- to late afternoon. 

Additional suggestions from Liz Leitman at SPC:

• Pick any ripe tomatoes. 
• Do laundry in case of extended power failures (quite likely in a derecho)
• Battery-operated fans for the same reason (it will be quite hot the next few days)