Changes to the Terminal Aerodrome Forecast


Well-Known Member
Hope it's not a repost... just a heads up from one of SLC ARTCC metos in charge.

Changes to the Terminal Aerodrome Forecast (TAF)

On February 1, 2004, the National Weather Service (NWS) implemented
changes to the TAF. The important changes for General Aviation (GA)
pilots, flight instructors (CFI), and other users of the TAF are:

1. Eliminate BECMG (Becoming).
2. Eliminate the use of PROB40 (40% probability of the specified
weather occurring).
3. Restricting the use of PROB30. The PROB30 will not be used in the
first 9 hours of the TAF, including amendments. (Previously it was not
allowed during the first 6 hours of the TAF).

The GA community, specifically pilots and flight instructors when flight
planning and decision making, should keep in mind that the TAF should
not be their sole source for a forecast of thunderstorms or rain or snow
shower at an airport, or along a route of flight. If the forecaster
feels the probability of thunderstorms and other precipitation events,
including any associated lower ceilings and visibilities, is less than
50 percent during the first 9 hours of a TAF, the TAF will not contain
that weather. If the forecaster believes the probability is 50 percent
or greater, the forecaster will include the weather in the TAF by using
a TEMPO (temporary conditions between the time stated) or FM (voiced as
"from", and meaning the prevailing weather will change at that time).

For flight planning and decision making, GA pilots and CFIs should use
all available weather information, and not limit their decision on one
product, i.e. the TAF. Just as in instrument flying, a pilot does not
focus on one instrument, rather the pilot scans several instruments.
The weather savy GA pilot should adopt the same procedure, which is to
look at several weather products and forecasts. For example, in
addition to the TAF, also use the Area Forecast (FA), NWS and other
Internet forecasts, television and radio weather forecasts, and
briefings from Flight Service Stations (FSS).

Thanks to the Internet, self briefings are becoming easier, but unless
you're a weather expert, don't omit the most important source for
weather, the Flight Service Station. I use FSS, and I'm a weather expert!


Partner, Ally, Friend
Seems almost counterproductive to me. If the forecaster feels there's even a slight chance of thunderstorms, ice, fog, whatever, I'd rather have that prob40 or prob30 in there to let me know. Now the TAF leaves you in the dark unless the probability is more than 50%.

So what's the point? Are they trying to limit the usefullness of the TAF in order to encourage pilots to get an FSS briefing? Do they need to cut down on the length of the TAF for some reason?


Well-Known Member
Sorry man, I never talk to FSS unless I can't find a computer. I can get everything I need to know off the net. I've spent too much time talking to briefers who just wanted to get it on the tape that they told me not to go.

Flight watch is a great service, though, my computer doesn't work too well in the plane.


Staff member
It's all about prog charts, baby!

[/ QUOTE ]

I still like the old days before AFSSs, where you could go talk to a briefer, and in the example of AZ, there was more than Prescott FSS (PHX and TUS, to name a few). I'd go into TUS FSS and they'd have all the progs, WX depictions, and radar summary charts colored in by highlighter and posted onto the wall, with the previous 5 or 6 behind that in order to get a little trending info.

Was neat.


Well-Known Member
I agree with Alchemy. There are many many times when the only weather information is the TAF, METARs, and SIGMETS/AIRMETS that are printed on my dispatch release. I don't have time on a 30 minute quick turn to call my dispatcher and have him run through his interpretation of the wx maps on his computer. Nor does he have the time to do that for the 10 flights he may be working at the time.

We all need that WSI datalink that I see in the magazines in our airplanes. Maybe the FAA should subsidize that. Yeah, right!