How do airlines handle SIGMETS?

Question

In general, what is the action taken by airlines when presented with a SIGMET in the projected route. Will they go around it, cancel the flight prior to takeoff, or simply fly thought it anyway?

As an example, there is a large SIGMET over the Sierra Nevada mountains right now due to high winds causing wind shear and moderate to severe turbulence. Knowing that severe turbulence can be a serious issue, would airlines, in general, cancel the flight, go around the area or simply fly anyway?

WSUS06 KKCI 250040
WS6N
SFON WS 250040
SIGMET NOVEMBER 2 VALID UNTIL 250440
CA NV
FROM 80N FMG TO 30ESE OAL TO 60NE EHF TO 50ESE RBL TO 80N FMG
OCNL SEV TURB BTN FL280 AND FL410. DUE TO WNDSHR ASSOCD WITH JTST
AND MTN WV ACT. RPTD BY ACFT. REPLACES NOVEMBER 1. CONDS CONTG
BYD 0440Z.

Source: aviationweather.gov

Answer 1

Your options, as you pointed out, are either to climb over this area, To go around it, to go under it, or wait until the segment expires or is expected to subside.

Another option available would be taken by this information with PIREPS. What are pilots reporting happened to them in this air space at this time? The SIGMET noted that there was occasional severe turbulence expected in that area which is pretty vague. If there are a very large number of PIREPS widespread throughout that block of airspace, it’s a good bet that it is very turbulent throughout and may not be a good idea to penetrate it. If the PIREPS are few and don’t repeat much turbulence in that airspace, then it may be advisable to fly through. Just keep the speed at that recommend by the manufacturer for penetrating turbulence and keep the fasten seat belt signs on.

Answer 2

The chart you linked is not a SIGMET, it is a prognostic chart.

To answer your question, it depends on the nature and location of the weather. In the case of the example, nothing shown would stop a flight because the weather top is low enough that they fly over it. Also, the ceiling is high enough that they can easily land.

Normally, flights are only cancelled if visibility is zero or there is a storm right over the airport. On a prog, you look for stuff like this:

If this is right over the airport, then that is bad. If there is a storm on the flight path, then they just go around it.