IFR Alternate Weather Question?

[BusDriver]

Please help settle my debate:

May you take credit for an alternate served by an AWOS?

I say yes, but can't find the reference in the AIM.

Thanks in advance.

[cggnl]

Do the AIM say you can not take advantage?

There is your answer.

Alternates can be filed based on the GFA also

Rgds

[turbo-prop]

You would need a favorable GFA an AWOS can't be depended on.

[Rockie]

AWOS's in Canada must be approved for aviation use. But alternates are selected based on forecast not actual weather, so I would say you can use an airport with an AWOS provided the weather is forecast to be above alternate limits at time of arrival. You can use a TAF, GFA or Airport Advisory forecast, but the last two have their own specific weather limits.

[cggnl]

You would need a favorable GFA an AWOS can't be depended on.

Neither can Enviornment Canada !


Rgds

[ahramin]

Whether it has an AWOS or not has no bearing. If it has a TAF then that is what you use for determining if it will meet alternate minima. If it does not then use can use the GFA with certain provisions.

[55+]

Please help settle my debate:

May you take credit for an alternate served by an AWOS?

I say yes, but can't find the reference in the AIM.

Thanks in advance.

The short answer is yes. If the alternate airport has a published(CAP/RCAP) IAP(Instrument approach procedure), said approach is based upon a certified altimeter source(remote, part time) and that can be AWOS, observer(certified) or a combination of both.

All IAPs have an approved altimeter source>

[ei ei owe]

The short answer is yes. If the alternate airport has a published(CAP/RCAP) IAP(Instrument approach procedure), said approach is based upon a certified altimeter source(remote, part time) and that can be AWOS, observer(certified) or a combination of both.

I didn't know AWOS could provide a forecast into the future.

[Icebound]

I didn't know AWOS could provide a forecast into the future.

LOL.

Isn't it interesting how, having been confronted with an irrelevant question, we confuse the questioner with irrelevant answers.

Note to FluckMachine and others:

FILING an alternate requires that it is expected to be "above limits" at the time of arrival based on: forecast weather, Forecast weather, FORECAST weather.

Not AWOS, not observer, not WeatherChannel, not Newspaper, not anything...

..except TAF, or in the absence thereof, then GFA properly interpreted (RAC 3.14)

[altiplano]

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[altiplano]

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[Icebound]

I didn't know AWOS could provide a forecast into the future.

METAR/TAF
EDMONTON CITY CENTRE/EDMONTON CITY CENTRE(BLATCHFO)/AB

TAF CYXD 182338Z 190012 13015G25KT P6SM FEW030 SCT150
FM0400Z 14012KT P6SM SCT120 BKN250 PROB30 0409 VRB15G30KT 3SM
TSRA BKN030CB
RMK FCST BASED ON AUTO OBS. NXT FCST BY 06Z=

I guess so...

It is a prerequisite that TAFs can only be issued for airports that have "a regular and complete observation program that meets Environment Canada standards..." Where that requirement is met by means of a fully automated (rather than human) observation, the forecaster is required to add that (somewhat misleading) notation which you highlight.

The notation does not say that the forecast is "based" strictly on the automated observation. It only means that the airport provides automated and not human observations.

The forecast is actually BASED on lots of things: past and present observations, historical observations at the "upwind" stations, satellite pictures, radar, global computer models, hemispheric computer models, local computer models, statistical inferences, plus, of course... the mood of the forecaster.

One of the reasons that this notation is made, is because the forecaster is supposed to realize the shortcomings of automated observations. Therefore, he may not have given the actual observations much weight, when preparing the forecast. This notation is added to the TAF to warn the pilot of that possibility.



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