The METAR Remarks Section, the Automated Station Flag, and the Encoded Data Most Pilots Stop Reading Too Soon

Most pilots stop reading a METAR at the altimeter setting. Everything after RMK - the remarks designator - gets skipped. That habit leaves critical weather information on the table, including data that can change a go/no-go decision.

Why Does the METAR Remarks Section Matter?

The structured METAR body - identifier, time, wind, visibility, sky condition, temperature, altimeter - follows a strict international format. That format is efficient, but it has limits. The remarks section is where the observation gets specific: information the structured body cannot encode, presented in a consistent and learnable format.

Once you know the key fields - AO designation, PK WND, PRESRR/PRESFR, variable ceiling, sector visibility, the T group, and SLP - a full remarks section reads in under 30 seconds.

What Do AO1 and AO2 Mean in a METAR?

AO2 means the station has an automated precipitation discriminator. The equipment physically distinguishes between rain, snow, freezing rain, and other precipitation types - it measures the actual character of what is falling.

AO1 does not have that capability. An AO1 station can detect that precipitation is occurring, but cannot identify what kind.

This distinction matters most in winter and near-freezing conditions. When temperatures hover near 2°C and METARs along your route show light precipitation, an AO1 station reporting RA (rain) is reporting an inference based on temperature - not a direct measurement. If the question is whether precipitation is liquid or frozen, an AO1 report cannot give you a confident answer. That uncertainty changes your entire icing exposure picture.

What Is TSNO and Why Should It Change How I Read a Forecast?

TSNO means thunderstorm not observed. It appears at AO1 stations that have no lightning detection equipment.

If a thunderstorm moved through during the past hour with no human observer present, the automated station may have logged precipitation but never recorded a thunderstorm code in the weather group. A cluster of AO1/TSNO stations reporting clear conditions is not the same as a human observer confirming clear conditions. Treat that distinction seriously when planning around convective weather.

How Do I Read the PK WND Field?

The wind in the METAR body is a two-minute average - a snapshot of current conditions. PK WND gives you the peak gust from the past hour, the direction it came from, and the exact time it occurred.

PK WND 28035/1427 decodes as: a peak gust from 280° at 35 knots, occurring at 1427Z.

Compare that time to the observation timestamp. If the current METAR is stamped 1505Z and the peak hit at 1427Z, that gust happened 38 minutes ago. Current sustained winds might show 12 knots - conditions appear to be calming. But something drove a 35-knot gust less than an hour ago. Is that system still in the area? Has the front passed, or is a squall line still working toward your destination?

PK WND does not answer those questions. It raises them. Raising the right questions during preflight is most of the job.

What Do PRESRR and PRESFR Mean?

Your altimeter setting tells you where the pressure is. It does not tell you where it is going. PRESRR and PRESFR fill that gap.

PRESFR (pressure falling rapidly) is flagged when pressure drops more than 2.0 millibars in less than two hours. That threshold signals a deepening low, an approaching front, or rapidly deteriorating conditions. If your destination METAR shows PRESFR during the planning phase, conditions there may not hold for the duration of your flight.

PRESRR (pressure rising rapidly) generally indicates post-frontal recovery - conditions trending toward improvement. Rising pressure does not confirm the front has cleared and skies ahead are open, but it does indicate the pressure gradient is shifting in a favorable direction.

How Do I Decode a Variable Ceiling in METAR Remarks?

The METAR body reports the ceiling at the moment of observation. It does not capture how that ceiling is moving.

CIG in the remarks, followed by two numbers separated by a V, means the ceiling oscillated between those altitudes during the observation period. CIG 005V010 means the ceiling has been bouncing between 500 and 1,000 feet.

If you plan around a reported ceiling of 800 feet, the remarks might tell you it reached 500 feet in the same reporting period. For an approach where the instrument decision altitude is above 500 feet, variable ceiling behavior below that threshold matters. A ceiling that averages 800 feet but varies by 500 feet creates a fundamentally different risk picture than a stable ceiling holding at 800.

What Is Sector Visibility in METAR Remarks?

The METAR body reports prevailing visibility - the dominant direction. When visibility is reduced in a specific direction from the airport, the remarks identify it.

Sector visibility appears most often at airports near water, terrain, or persistent smoke sources. The body gives you the prevailing number; the remarks tell you which direction that number breaks down. If you are departing or arriving from a direction with reduced sector visibility, the METAR body understates your actual conditions.

How Do I Decode the T Group for Precise Temperature and Dewpoint?

The T group provides temperature and dewpoint to the nearest tenth of a degree Celsius - more precise than the whole-number values in the METAR body.

The character after T is 0 for above freezing, 1 for below freezing. The next three digits are the temperature in tenths. Then the same structure repeats for dewpoint.

T01720092 decodes as:

• 0, then 172 → positive 17.2°C temperature
• 0, then 092 → positive 9.2°C dewpoint

Temperature/dewpoint spread is a primary fog predictor. A spread of 8.0° and a spread of 7.2° both round to the same whole number. On a calm, clear night approaching saturation, that eight-tenths of a degree gap represents meaningful time before fog forms. For density altitude calculations at high-elevation airports in summer heat, precise temperature values affect performance numbers in ways that rounded figures cannot fully capture.

How Do I Decode SLP (Sea Level Pressure)?

SLP gives you barometric pressure normalized to sea level in millibars, to the nearest tenth, encoded in three digits.

Decoding rule: if the three digits are 500 or higher, prepend 9. If less than 500, prepend 10.

• SLP985 → 998.5 mb
• SLP031 → 1003.1 mb

Your altimeter setting is already in the METAR body in inches of mercury. SLP provides the same pressure in the standard meteorological unit, useful for comparing against surface analysis charts and understanding pressure system geometry along your route. SLP also functions as a cross-check: your altimeter setting and SLP value should convert consistently. If they do not agree, the observation warrants a second look.

Putting It All Together: A Practical METAR Remarks Example

Here is a METAR from a mid-sized regional airport with recent frontal activity:

KXYZ 1855Z 33014KT 10SM FEW020 BKN040 17/09 A2986 RMK AO2 PK WND 34026/1822 PRESRR SLP031 T01720092

The body looks comfortable: winds from the north-northwest at 14 knots, 10 miles visibility, few clouds at 2,000 feet, broken ceiling at 4,000 feet. Nothing alarming.

Now the remarks.

AO2 - automated station with precipitation discriminator. Any precipitation type in this report is a measured observation.

PK WND 34026/1822 - peak gust from 340° at 26 knots at 1822Z. The observation is stamped 1855Z. That peak hit 33 minutes ago. Current sustained winds are 14 knots - whatever drove that gust has partially wound down.

PRESRR - pressure rising rapidly. Now the peak wind has context. A frontal passage moved through. Northwest winds kicked up, pressure spiked, and rapid post-frontal recovery is underway. The body showed calming winds and acceptable ceilings. The remarks reveal a front that just passed and conditions actively improving. Those are different pictures.

SLP031 - 1003.1 mb. Consistent with the altimeter setting of 29.86 inHg. The numbers check out.

T01720092 - temperature 17.2°C, dewpoint 9.2°C. Spread of 8.0°. No immediate fog threat.

What did the remarks add? A cause. A frontal passage moved through within the past hour, winds peaked at 26 knots, and conditions are recovering. But that front is now moving northeast. If the planned route goes northeast, you may be flying toward the deteriorating conditions this airport just came through. The remarks started the conversation. A thorough weather briefing finishes it.

The Difference Between Decoding and Interpreting

Stopping at the altimeter is decoding. Reading the whole report is interpreting.

The Airman Certification Standards ask pilots to use weather information effectively. Effective use means asking why a METAR looks the way it does - what caused these conditions, are they improving or deteriorating, and what does this observation tell you about the weather you are flying toward?

The remarks section is where you start answering the why. An examiner is not grading your ability to decode. They are grading your ability to interpret.

How to Build a Full-METAR Reading Habit

The remarks section looks intimidating on first encounter: characters strung together with no obvious separation, no labels, no punctuation. But once you know the anchors - AO designation, PK WND, PRESRR/PRESFR, variable ceiling (CIG), sector visibility, the T group, and SLP - the section develops into a readable scan.

Pull live METARs from stations along your planned routes at the Aviation Weather Center (aviationweather.gov) and read every field top to bottom. The full METAR remarks code list is in Federal Meteorological Handbook No. 1. Plain-language explanations with examples are in FAA Advisory Circular 00-45H, Aviation Weather Services. Both are publicly available through the FAA and National Weather Service.

Key Takeaways

• AO1 stations cannot identify precipitation type. In near-freezing conditions, “RA” from an AO1 station is an inference, not a measurement - critical for icing exposure decisions.
• PK WND reveals what the two-minute average hides. A peak gust from within the past hour may reflect a system still affecting your route.
• PRESFR is an active go/no-go input, not background data. A drop of more than 2.0 mb in less than two hours signals rapidly deteriorating conditions at that station.
• Variable ceiling (CIG) and sector visibility describe how conditions behave between observations - information the METAR body structurally cannot encode.
• The T group and SLP add precision for fog prediction, density altitude performance, and cross-checking observation integrity.