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) provides automated, localized weather forecasts for over 2,100 airports, significantly more than TAFs, by statistically refining raw model data with geoclimatic information to account for local conditions.
It offers detailed aviation-specific weather elements like ceiling, visibility, and wind, making it valuable for airports lacking official TAFs or to supplement existing forecasts.
However, MOS is an automated product and **cannot legally replace human-issued TAFs** for critical flight planning decisions (e.g., alternate requirements) and has specific limitations regarding forecasting multiple cloud layers, precipitation intensity, and variable winds.

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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.