10:20pm CDT Update Derecho, With Tornado Threat, Kansas to Ozarks

10:25pm Forecast Update

Here is my forecast from now until 3am. In supercells ahead of the line of thunderstorms, a tornado is possible and it is also possible a tornado could be embedded in the derecho. The air is highly unstable over south central Kansas and (for meteorologists): The 0-1km SRH at Wichita is 319 and has been rising. 

Please make sure you have at least three ways of receiving warnings during the night. Power outages are certainly possible. 

8pm Update:

I agree with the addition of tornadoes to the threat. Data the last few hours indicates they are a possibility. NWS is forecasting gusts to 80 mph, I think 90 mph is possible in a few places. NWS is also forecasting tennis ball-sized hail. Note: NWS in Goodland, KS just issued a severe thunderstorm warning for 100 mph winds! This is a serious situation. 

Please make sure you have at least three ways of receiving warnings during the night,. Power outages are certainly possible. 

5:30pm Update:

This is Part 1 for the Ozarks. The forecast derecho will be late tonight or Sunday morning. In the meantime, tornadoes, tennis ball-sized hail and 70mph winds are possible until 1am Sunday. 

NWS has just posted a severe thunderstorm watch for 85 mph winds and tennis ball-sized hail. 

It is in effect until 7pm MDT / 8pm CDT. 

--- original posting, still valid ---

Fifty years ago at this time when we were preparing for that afternoon and evening's onslaught of tornadoes, we had never heard the term derecho. We knew there were long-lived wind events but no one had realized they were a distinct type of event until the 80's. 

It appears there is a good chance of a derecho starting in Colorado late this afternoon that will sweep across Kansas this evening and tonight, and then across the Ozarks late tonight and Sunday morning. Here are the specifics:

Wind Forecast

Here is the color code:

• Red = enhanced risk of wind gusts of 60 mph or stronger. 
• Yellow  = significant risk of wind gusts of 60 mph or stronger 
• Hatching and Horizontal Lines = where wind gusts of 75 mph or stronger are forecast to occur. My forecast is that wind gusts of 95 mph are possible. I also think 75 mph or stronger winds may extend east to nearly the Missouri border. 

A couple of tornadoes may occur in the High Plains part of this forecast but the derecho winds are the primary threat. Large hail is also possible, especially in Colorado and in Kansas west of Highway Highway 183.

Timing

The   _ .. _ ..   is a meteorological symbol for a line of thunderstorms.  

Preparation Suggestions:

• Put your car and lawn furniture, et cetera, in the garage or indoors before the storm arrive. 
• Power outages are likely. Charge your laptop and smartphone but take them off the chargers when you see the first stroke of lightning or hear the first peal of thunder. 
• Make sure you have batteries for flashlights, etc. In a power failure, use battery powered lightning rather than candles due to the fire hazards. 

When a wind warning is issued for your area, get indoors and away from windows. 

I will update the forecast late this afternoon. I'll provide real-time warnings on Twitter @usweatherexpert.