What Is a MOS Forecast?

For an airport without a TAF, a MOS forecast can provide some useful guidance about expected meteorological conditions—but it has some limitations.

Scott Dennstaedt, Ph.D

Wednesday, October 04, 2023 at 05:09 PM ET

Verified

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Key Takeaways:

MOS (Model Output Statistics) is an automated forecast tool in EFBs that provides aviation-specific weather guidance for over 2,100 airports, significantly more than official TAFs.
It statistically combines raw weather model forecasts with geoclimatic data to account for local conditions and produce aviation-relevant elements like ceiling height, visibility, and wind.
While valuable for supplementing information at airports without official TAFs, MOS is *not* a legal replacement for human-issued TAFs and should not be used for IFR flight planning requirements like alternate minimums.
MOS has specific limitations, such as inability to forecast multiple cloud layers, precipitation intensity, or variable winds; the LAMP program is the currently supported version mentioned in FAA literature.

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Question: The EFB I use has an option for MOS forecasts… What is that and can that be used legally for planning a flight?

Answer: MOS stands for model output statistics and is pronounced “moss.” MOS has been around since the 1960s and was originally developed to provide aviation meteorologists with guidance to produce useful forecasts to pilots. But over the last decade, MOS has been making its way into the aviator’s toolkit and is offered by a couple of the heavyweight electronic flight bag (EFB) apps.