Monday, November 09, 2015

Wednesday Weather Worries



Here we go with another round of fall thunderstorms as our secondary severe weather season is in high gear.  Thankfully, the last round of storms wasn't all that bad.  As we focus on this next round, there are a couple things that really stand out to me as I analyze the data.  First, the system Wednesday is a quick mover.  Second, the corridor for severe weather potential over Arkansas is quite narrow as instability will be in question.  Since this system will move quickly and the area of thunderstorm potential will be narrow, I don't expect flooding to be an issue.

There are other factors we need to consider.  This is a very strong area of low pressure moving into the central United States.  The air aloft is super cold.  This can help promote the development of severe weather.  All of the models agree the track of the low should be well north of the state.  I think it's closer to that track where you will find the worst weather.  So northern Arkansas up into Missouri will really need to watch this.   That does not mean other areas of the state are immune and things can't change since it's a couple days away.

Satellite imagery over the eastern Pacific shows the storm system quite well.  When you see this cloud pattern circled, it indicates very cold air aloft and the potential for deep convection (big storms).  I worked in western Montana for a couple of years straight out of college.  When these strong areas of low pressure aloft worked through (cold air aloft), we would get convective snow showers.  Lift from the mountains would also enhance their intensity.  I would be quite common to pick up several inches of snow in a very short amount of time in the higher elevations.  I was hiking once and got caught in one of these.  It came with a little thunder and lightning too.  Wild!!!!  At times, these convective snow bands would work into the valley areas of western Montana.  I remember quite well watching a wall of white moving towards me.  I picked up 2 inches of snow in 20 minutes from one of those snow squalls.  It was crazy.   I couldn't see my hand in front of my face.  Anyway, my point is this... the pocket of cold air aloft moving on top of relatively warmer surface temperatures will be conducive to promoting thunderstorms here.  NO SNOW though. LOL.  However, watch eastern Colorado and the Denver area.  They will have snow.
Here's the GFS valid late Wednesday at the surface.  The area of low pressure is well north of the state in Iowa.  The blue area is instability.  Notice it's in a narrow corridor from the Gulf up into the low.  Also instability values are not that high, however, there are times when the models underestimate this value.


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