[This content is courtesy of John Zimmerman at Air Facts Journal.]

All pilots are required to conduct a weather briefing before each flight, whether that means calling Flight Service or looking up the weather online. But for true weather geeks, a pre-flight weather briefing can be a lot of fun, not just a requirement to be completed as quickly as possible. And for pilots looking to go beyond the basics, there is a wealth of information online with details about ceilings, visibility, turbulence, icing and more.

Everyone has their list of favorite weather sites. Here is my top 10 list of useful weather websites that aren’t as well known as they should be (and they’re all free):

1. Graphical AIRMET tool
AIRMETs have a well-deserved reputation for being fairly worthless. They are hard to understand unless you can see them on a map, and they often warn of turbulence over half the country. But this new tool rescues the AIRMET from the trash bin, with some nice enhancements to the classic product. For example, you can quickly overlay multiple AIRMETs (low level turbulence, high level turbulence, icing, etc.) on the same chart, and you can view predicted AIRMET coverage areas about 12 hours into the future. It’s a nice way to view the trend, so you can get a feel for whether conditions are improving or deteriorating. It’s also easy to hide AIRMETs that don’t affect your flying (for example, high level turbulence if you fly a Cessna 172).

2. TAF graphics.
The Terminal Aerodrome Forecast (TAF) is a valuable product, and is used by pilots of all levels. While the text has all the important details, sometimes a visual depiction of TAFs can offer clues about how widespread low ceilings are or what the trend is for low level winds. The TAF graphic makes it easy to view this information on a single chart, at three hour intervals in the future. You can also look at a single weather features–clouds, weather conditions, forecast winds and wind gusts–over time. This is an experimental product right now, and you’ll want to read the actual TAF for complete details, but there is a lot of information here at a glance.

3. Medium range forecasts.
Most aviation weather sites show the prognostic charts, with high/low pressure centers and fronts, up to 48 hours out. But sometimes you want to get an idea about the weather further out than just two days. That’s where this site, from the National Weather Service, comes in. It offers 3-7 day forecast graphics on a simple-to-use page, and you can even loop the images. The further out a forecast goes, the less reliable it tends to be, so you’ll want to use these charts as a general guide. But for long trips a few days out, I’ve found this to be a helpful tool.

4. CWSU national map.
This map is my favorite all-in-one tool for looking at surface weather trends. This nationwide map graphically shows all METARs, including ceiling, visbility, cloud cover, wind direction and speed and other data. You can mouse-over a station for current weather conditions and the TAF. Clicking on a station brings up an detailed page with the last 24 hours of weather information, including some graphs. This is an invaluable tool for VFR pilots planning cross-country flights, and even IFR pilots when faced with low visibilities. It’s a great way to find an alternate airport, too.

5. Historical METARs.
Have you ever completed a flight and wondered a few days later what the weather really was? Or maybe canceled a flight and wished you could see how it really turned out? This site, definitely for the real weather geek, has METARs archived all the way back to July 30, 1998. You pick the state, the date and the time and you’ll get a list of the METARs at that time. This isn’t really a pre-flight tool, but it’s an excellent way to learn about weather and improve your own forecasting.

6. C&V chart.
This is a slightly different take on the graphical METAR idea. Here, the chart tries to fill in the blank spots between airports, so instead of station plots you can see wide areas of ceiling and visibility restrictions. This is obviously an educated guess, but it can give the VFR pilot a reality check on low weather days, especially when METARs are widely scattered.

7. Skew-t/log-p charts.
Skew-t plots are where serious weather geeks really get excited. They are certainly not easy to read, and I wouldn’t argue that they be part of every pre-flight briefing. But they are educational and can offer some important clues for pilots, especially if you’re interested in convection or icing threats. The Skew-t chart, among many other things, shows the temperature, dewpoint and wind speed at different altitudes. With some practice, these graphs can reveal how stable the atmosphere is, where wind shear may exist and even how thick a cloud deck might be. There are a number of websites that provides Skew-t plots, but the RUC Soundings site from NOAA is the most powerful. You can view forecast Skew-t/log-p plots, and center it on an airport by entering the identifier. Be sure to click “Java-based plots” for the most full-featured display.

8. Full resolution looping NEXRAD.
Probably every pilot checks the radar before flying, and there are plenty of options for this. But this site is the full resolution image from NOAA, and it shows the entire country (you can even loop the image). It’s a big page, but it’s a fantastic look at the latest picture, and my go-to during thunderstorm season. You can also click a location on this big map for individual NEXRAD site radars, where you can compare base and composite reflectivity. On this map, you can click for the lat/long, which I’ve found to be helpful for flight planning around airspace.

9. Turbulence and icing forecasts.
The threat of turbulence and airframe icing are usually high on the list of concerns for pilots. Up until a few years ago, the only way to plan for these events was to combine PIREPs, area forecasts and a healthy dose of gut feel. But the Aviation Weather Center website has recently added some great new forecast tools. They both operate similarly, allowing you to view the probability of ice or turbulence at different altitudes at different times in the future. These are obviously models, but in my experience they are quite accurate (especially the icing tool). If you canceled every time there was a cloud deck and the temperature was below freezing, you would never fly in some parts of the country. This tool allows you to make a better plan, potentially changing departure time, route or altitude to minimize your exposure. PIREPs are still piece of the puzzle, but these charts can add more detail.

10. Flight Path Application.
This is really a downloadable Java application, not a website, so it’s definitely for power users. But for education or serious flight planning, it has some unique features that can’t be done in a web browser. You can enter your route of flight, then view different weather products along your route. You can also see a profile view of your flight, including the graphical icing forecast (above), allowing you to choose the right altitude quickly and easily.

To stay up to date on the latest weather tools from NOAA, check the ADDS website occasionally. This is the place to preview new products that aren’t ready for full deployment yet, some of which can be very handy for flight planning.

On top of these great websites, there are some fantastic iPad apps if you’re a tablet user. I’ll save that list for another article, but I will mention that RadarScope is my favorite app when it comes to serious weather watching.

What’s on your list?