What Is an Outflow Boundary Shown on a Surface Analysis Chart?

Here's a step-by-step guide to deciphering surface analysis charts—particularly ‘gust fronts.’

Wednesday, May 01, 2024 at 12:01 PM ET

Verified

During the spring, summer, and fall, it is common to see the surface analysis chart issued by meteorologists at the WPC include dashed lines labeled as an outflow boundary. [Courtesy: National Oceanic and Atmospheric Administration.]

Key Takeaways:

Outflow boundaries, also known as gust fronts, are mesoscale cold fronts formed by cold, dense air spreading out from thunderstorm downdrafts, appearing as a tan dashed line on surface analysis charts.
These boundaries can pose significant hazards including severe turbulence, dangerous low-level convective wind shear, and strong straight-line winds, especially when moving in advance of their parent convection.
Pilots can identify outflow boundaries through surface analysis charts, METARs, ground-based NEXRAD radar (as low reflectivity lines), and visible satellite imagery (if moisture is present).
Outflow boundaries are low-level events often filtered out by datalink weather broadcasts and can be overshot by distant radar beams, requiring pilots to diligently monitor local radar and surface observations for safety.

See a mistake? Contact us.

Question: What is an outflow boundary shown on a surface analysis chart?

Answer: When looking at the surface analysis chart issued every three hours by meteorologists at the Weather Prediction Center (WPC), you may have seen a tan dashed line with a label “OUTFLOW BNDRY” nearby. This is what meteorologists call a convective outflow boundary.

You may view North American surface analysis here.