How to make a glow / color fade with PIXI.filters.GlowFilter?

I want to add a really big blue glow to the gray hold bar. This example looks pretty good but I want it to look less like a tight border and more like a stretched blue fade out. I tried to accomplish this by increasing the outer strength. 

let barContainer = new PIXI.Container();
barContainer.position.set(xPosition, 110);

let bar = new PIXI.Graphics();
bar.beginFill(0xffffff);
bar.tint = 0xbbbbbb;
bar.drawRect(0, 0, chordWidth, 10);

barContainer.addChild(bar);

let glowFilter = new GlowFilter(10, 2, 0, 0x00507c, 0.1);
glowFilter.padding = 100;

barContainer.children[0].filters = [glowFilter];

//increase outer strength to try and make the filter spread out farther
let glowFilter = new GlowFilter(10, 30, 0, 0x00507c, 0.1);

As cool of a border as this is, how can I make a glow filter that fades out? Is it possible with something as easy as GlowFilter or other filters?

Thank you for any help! 😁

P.S. I also tried the approach of using a gradient image as suggested in this topic but it didn't work very well with my rectangles that heavily vary in width.