Weather Briefings Can Be Your Friend

What’s the Cause?

Low ceilings, fog, precipitation, and weather below minimums (but not icing) contributed to 69 percent of all fatal weather-related accidents. This points to VFR flight into IMC, lack of IFR training, poor situational awareness, and the need to properly use available weather information. Icing, carb ice, and density altitude contributed another 18 percent of fatal accidents.

The Weather Briefing

How you approach the briefing is actually just as important as the information. Many pilots get stuck in a go/no-go mentality, which only provides a superficial look at things. The correct technique is to take in all the information, build a full mental picture of what’s happening along your route, and from there, decide how it will impact your flight.

Ceilings

Be aware of the distinction between MSL and AGL. Cloud heights associated with airports are customarily given in AGL. But area guidance products, area forecasts, and PIREPs, use MSL.

Mountain Obscuration

Controlled flight into terrain is disturbingly common, and it happens even to highly trained pilots. Of course, accurate navigation is critical in the mountains. Any combination of significant moisture and instability always means the potential for low ceilings and visibility in mountainous terrain.

Turbulence

Turbulence is easily anticipated. Mechanical turbulence is linked closely to strong surface-based instability, strong pressure gradients, and speed shear and directional shear in the lowest mile of the atmosphere. In mountainous regions, a rule of thumb for moderate or greater turbulence is winds over 20 knots near the tops of mountains and ridge lines, especially perpendicular to mountain ranges.

Wind

Sudden changes usually come from the approach of outflow boundaries, which can surge outward up to 30-40 miles from a storm and produce unexpected wind shifts. Pilots can’t really second-guess gusts in the models and TAFs, but anything that strengthens the differences between the surface winds and the winds at 1000 or 2000 feet will increase your risk of gusty runway conditions.

Icing

Danger areas are near and just above the freezing level, normally -5 to +10 degrees C. The go-to tool in meteorology is the Skew-T chart. The Aviation Weather website offers easy-to-read cross-sections under their Flight Path Tool that provide not only icing potential but temperatures, giving you a clear picture of safe and dangerous altitudes.

Convective Weather

Avoid thunderstorms. The FAA recommends remaining 20 NM outside thunderstorms. A study noted that the survivability of a GA accident in a thunderstorm is lower than 50/50.