Friday, April 25, 2014

Significant Severe Weather Possible

The more I look at this, the more I don't like it.  This could turn out to be the biggest severe weather event so far this season.  I'm confident there will be an outbreak of severe weather (wind and hail).  However, will there be an outbreak of tornadoes?  While the data points to that, I urge caution and hope it doesn't happen.  When I talk to schools I always teach what I call the "tornado cake".  If all the ingredients are present, tornadoes form.  If you're lacking just one ingredient, it doesn't turn out right and tornadoes don't form.  It's sort of like baking a cake.  You leave out the sugar and it's not happening.  While this is a couple days away, much can change.  What if the instability is lower than expected? There are many variables we will watch to see how this comes together.  Again, we are confident there will be severe weather, but an outbreak of tornadoes is questionable.  Looking at the data this morning, it's a definite possibility.  One more threat on the table is flash flooding.  A few inches will be possible.

The Storm Prediction Center has issued a rare moderate risk for severe weather in its 3 day convective outlook.  This indicates their high confidence severe weather will occur due to model agreement.

The severe threat may linger into Monday and Tuesday depending on how fast the front exits the state.  There are signs the upper flow may run parallel to the front.  This could stall the front keeping the threat for heavy rain and severe weather in the forecast Monday and again Tuesday.  The favored area at that time will be eastern Arkansas. Again, this is still subject to change so stay tuned.

Some of the maps below are from

This is the GFS indicating areas of rain and storms over the state between 7AM and 1PM Sunday.  While there will be the chance for some severe weather at this time, the greater threat arrives later in the day.
Rain and storms should increase over western and southwestern Arkansas between 1PM and 7PM.  The GFS is indicated much of this will be convective.  We can only hope instability values are not too high.
Between 7PM and 1AM Monday, the storminess shifts into eastern Arkansas.  However, notice the surface low is still over northern Oklahoma.  The front is still to the west and this could keep the atmosphere unstable going into Monday.
By Monday at 7AM, the front is still over eastern OK and the entire state is still in the "warm sector".  This opens the window to the possibility for more severe weather Monday.
By Tuesday morning at 7AM, the front barely moves and is located over NE to central and southwest AR.  This keeps the chance for severe weather in the forecast for areas along and ahead of the front as instability builds once again during the day Tuesday.  The target area will be eastern AR.  Again, I urge caution.  If the front speeds up, the severe weather threat will decrease for us.  Let's hope that happens.
Here's the risk area from SPC Sunday.
This is the risk area Monday as the front slows
And Tuesday as the front continues its slow trek across the state.
Flooding will be a concern.  At least 1-3 inches will be possible over that 3 day stretch.  The highest amounts will be across the eastern half of the state since they will be more susceptible to storms in the warm sector ahead of the front.


Anonymous said...

Todd I am very concerned about those camping or boating this weekend. Everybody needs to spread the word. Stay weather aware.

Seth Hardwick said...

I'm always hesitant about using the word outbreak, especially the term "tornado outbreak. It's just to vague, and subject to personal opinion. It also seems to cause panic, though not as much as when you mention "snow" lol.

If you got time, check out my full blog post on the term "outbreak" sometime.

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