To begin, pilots are almost never "trapped" by weather. Some will come up with a tale they think proves that they were "trapped," but you simply have to fly by too many clues to wind up in weather trouble without some sense of trespass.
So what is the biggest trap? Simple. The forecasts, or, the way that we use the forecasts.
Many of us look at long-range forecasts to get a sense of the weather for an upcoming trip. That is fine so long as we don't put much stock in those long-range forecasts. Any time you want to see how much uncertainty there is, just go to the forecast discussion on the NWS site for your area. (Go to noaa.gov and type in the name of your town.) Some of the forecasters go into greater detail than others but from reading the discussion for periods out more than about 24 hours, you can see that they deal mainly with generalities and have a lot of variables to deal with.
That basically tells us what we need to know about forecasts. They are guesses, based on history. Educated guesses to be sure, but they don't deal with realities. As pilots we do have to deal with the reality of conditions as they develop.
How does this transfer to flying?
To begin, it's not a good idea to use forecasts in isolation. The terminal forecasts (TAFs) attempt to predict the weather for only a little bit of the air, that within five statute miles of the airport, and they look ahead for only 24 hours. They are issued every six hours, starting at 0000Z.
The bigger picture can be found by considering other forecasts offered to pilots.
A bigger look at the weather comes from the six area forecasts (FAs) that cover the 48 contiguous United States. These include a synopsis of weather features such as fronts and lows, and forecast general weather conditions over an area. Be careful about what you are looking at when it comes to cloud heights as the FA gives them both in height above the ground and height above mean sea level, and specify which is used. There is also word on flight precautions that are addressed in airmets (WA) and sigmets (WS).
The airmets forecast various weather phenomenon of concern to pilots and come in Sierra for IFR conditions or mountain obscuration, Tango for moderate turbulence or surface winds of 30 knots or greater and/or non-convective low-level wind shear, and Zulu to cover moderate icing and predict freezing level heights.
