<p>If they propagate outward from thunderstorms, they are outflow boundaries. Cold air flows down from the thunderstorm with precipitation and spreads outward upon hitting the ground. This air moves ahead of the storm and forces warmer air upward, suspending clouds and other particles. That's what is visible on radar.
More: <a href="https://en.wikipedia.org/wiki/Outflow_boundary" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Outflow_boundary</a></p>

CC BY-SA 4.0
2020-05-11T18:43:18.943Z
2020-05-11T18:43:18.943Z
Bob Smith
<p>I frequently see lines like this (the red arrows in the image below point to what I am referring to) on doppler radars. They are usually propagating outward from a line of thunderstorms.</p>
<p>What are they, what do they indicate, and how do they form?</p>
<p><a href="https://i.sstatic.net/JOlxI.png" rel="noreferrer"><img src="https://i.sstatic.net/JOlxI.png" alt="Doppler Radar Image" /></a></p>

<meteorology><radar>
What are these lines that I frequently see on doppler radar?
magicmq
# What are these lines that I frequently see on doppler radar?

(Asked by: username_0 on 2020-04-09)

I frequently see lines like this (the red arrows in the image below point to what I am referring to) on doppler radars. They are usually propagating outward from a line of thunderstorms.

What are they, what do they indicate, and how do they form?

[![Doppler Radar Image](https://i.sstatic.net/JOlxI.png)](https://i.sstatic.net/JOlxI.png)

**Tags:** meteorology, radar


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## 1 answers

### Answer by username_1 on 2020-05-11. Score: 3

If they propagate outward from thunderstorms, they are outflow boundaries. Cold air flows down from the thunderstorm with precipitation and spreads outward upon hitting the ground. This air moves ahead of the storm and forces warmer air upward, suspending clouds and other particles. That's what is visible on radar.
More: <https://en.wikipedia.org/wiki/Outflow_boundary>


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