The Area Forecast Discussion

Area Forecast DiscussionThere’s a little-known weather product out there that is actually pretty helpful- the Area Forecast Discussion, or AFD. This little beauty has been around for a while but I had never heard of it until Foreflight started to include it in the weather section of their excellent software. Since I can’t write a better description than the Foreflight people, I will instead quote them directly:“The AFD is a discussion that is written by the same forecasters that issue the TAFs. Every NWS local Weather Forecast Office (WFO) throughout the United States issues terminal forecasts for airports that appear within their County Warning Area (CWA), hence the term Area Forecast Discussion.After TAF issuance, meteorologists are required to update the AFD with a plain english discussion explaining their thoughts behind the forecast which allows them a plethora of ways to quantify their uncertainty. AFDs were originally designed as technical discussions to enhance collaboration among NWS forecast offices and to convey uncertainty to a specialized audience.”

Basically, it’s a plain english explanation of the reasoning behind the published TAF. Why would that be important? Well, as in everything else, there are rules, guidelines, and criteria that apply to the finished product. The discussion allows us a peek behind the curtain, so to speak. For example, at the time of this particular article, this is the TAF for the area:

KCHS 241121Z 2412/2512 32007KT P6SM SKC FM242300 00000KT P6SM SKC

That gives us all the information we need, but the discussion goes like this:

Extended aviation outlook…VFR through Tuesday night. The probability for flight restrictions increases Wednesday through Thursday.

Or, how about this AFD entry from the service based at Lincoln, IL:

“Predominantly VFR aviation weather conditions expected across the central Illinois terminals through the 12Z valid time. However, as a storm system approaches the area late tonight, IFR stratus/fog may develop, especially at KPIA, KBMI, & KSPI.”

The TAF for the same time period? “NO DATA FOUND”

Understand, I am not suggesting that you substitute the AFD for the TAF- rather, treat the AFD as the clarifier, because sometimes it will contain information that is unclear, or even non-existent, on the TAF. How could that be?

According to the Foreflight article, “… meteorologists at the local weather forecast offices that issue forecasts for high impact terminal areas such as Charlotte Douglas have a fair amount of outside pressure from the airlines to avoid adding thunder to the forecast unless convection is fairly certain. A forecast for thunder at the proposed time of arrival means the airlines must file an alternate and carry extra fuel to get to that alternate.”

Hmmm…so, they might be pressured to avoid the mention of a thunderstorm, but as a pilot, my need to avoid the actual thunderstorm is even greater, so a peek at the AFD might be beneficial to us non-carrier people. The AFD is where I will see those possible thunderstorms clearly discussed.

By the way, Foreflight is now adding AFD information under the weather tab, so Foreflight users can now easily access this product. If you are not a Foreflight user, you can bookmark this link and add it to your weather toolkit- it’s now a standard for me.

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