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 detailed, location-specific aviation weather forecasts for over 2,100 U.S. airports by combining raw model data with geoclimatic information.
It is useful for filling in gaps where official Terminal Aerodrome Forecasts (TAFs) are unavailable, offering guidance on aviation-significant weather elements like ceiling, visibility, and wind.
As an automated forecast, MOS should not legally replace a forecaster-issued TAF for operational decisions (e.g., alternate requirements) but serves as a supplementary tool.
MOS has limitations, including inability to forecast multiple cloud layers, distinguish definite/indefinite ceilings, predict "vicinity" phenomena, or 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.