Decoding +TSGR, -RA, and FZRA

The present-weather group sits between visibility and the cloud layers in a METAR, and it is the only field that is read as a small sentence rather than a number. The plus and minus prefixes set intensity, so +TSGR is a heavy thunderstorm with hail and FZRA is freezing rain that signals airframe icing. Once you treat each group as intensity, then descriptor, then phenomenon, even a dense string like -FZRA BR decodes cleanly, and wxdecoder expands each token into a labeled line.

This guide covers the three-part construction, the intensity and proximity qualifiers, every descriptor, the phenomenon tables, and the combination rules that keep the codes legal. It is part of the METAR field guide; for the icing side of the story, see why dewpoint spread matters.

The three-part construction

Every present-weather group is built left to right from up to three parts:

[intensity/proximity] [descriptor] [phenomenon]

• Intensity or proximity is a single qualifier: - for light, nothing for moderate, + for heavy, or VC for the vicinity of the station.
• Descriptor is a two-letter modifier such as TS or FZ. At most one descriptor appears per group.
• Phenomenon is the precipitation, obscuration, or other event itself, such as RA or GR.

A group can carry one, two, or three parts. RA is just moderate rain. -RA is light rain. +TSRA is a heavy thunderstorm with rain. Multiple groups can appear in one METAR, separated by spaces, and they are listed roughly in order of significance.

Intensity and proximity

The leading qualifier is the most misread part of the group, because moderate has no symbol at all:

Intensity applies to precipitation. VC reports weather observed near the field but not over it, for example VCTS for a thunderstorm in the vicinity, and it never takes an intensity sign. RE marks weather that has recently ceased, which you will see more often in ICAO reports than in US ones. So -SN is light snow, SN is moderate snow, +SN is heavy snow, and VCSH is showers in the vicinity.

Descriptors

A descriptor refines the phenomenon that follows it. There are eight, and each has strict pairing rules covered in the next section:

TS and SH describe how the precipitation is delivered. FZ is the one that matters most for safety, because it means the water is supercooled and turns to ice the instant it touches the airframe or runway.

Phenomena

The phenomenon is the actual weather. The codes split into precipitation, obscuration, and a short list of other events.

Precipitation:

Obscurations:

Other phenomena:

UP is worth a note: it is reported by automated stations that detect precipitation but cannot classify the type. If you see UP, the station knows something is falling but not what, which is one reason raw reports stay valuable next to any automated summary.

Combination rules

The codes are not free to combine in any order. A handful of rules keep them legal, and knowing them tells you what a group can and cannot mean:

• FZ pairs only with RA, DZ, and FG. That gives you FZRA (freezing rain), FZDZ (freezing drizzle), and FZFG (freezing fog). All three mean ice forming on contact, so all three are icing reports.
• MI, BC, and PR attach only to fog. They describe how the fog sits on the field: MIFG shallow fog, BCFG patches of fog, PRFG fog over part of the field.
• DR and BL attach only to snow, sand, and dust. Drifting and blowing are about loose material lifted by wind, as in BLSN (blowing snow) or DRDU (low drifting dust), never about rain.
• FG and BR are the same water, split by visibility. Below 1000 meters it is FG (fog); at or above 1000 meters it is BR (mist). The visibility group and the present-weather group should agree on which side of that line you are on.

Decoding +TSGR

Take it one part at a time:

+TSGR

• + is the intensity: heavy.
• TS is the descriptor: thunderstorm.
• GR is the phenomenon: hail, the variety larger than 5 mm.

So +TSGR is a heavy thunderstorm with hail. Operationally this is among the most hostile lines a METAR can show: a thunderstorm brings the squall, lightning, and wind shift, and GR confirms hail large enough to damage an airframe. A thunderstorm also implies deep cloud and rapidly changing ceilings and visibility, which is why a report like this usually rides alongside a low flight category and, often, a vertical visibility group when the obscuration becomes indefinite. Read +TSGR as a stop-and-reassess signal rather than a single data point.

Decoding FZRA

FZRA

• No leading sign, so the intensity is moderate.
• FZ is the descriptor: freezing, meaning supercooled.
• RA is the phenomenon: rain.

FZRA is moderate freezing rain. The water is liquid in the air but below freezing, so it turns to ice the moment it lands on the wings, the windscreen, or the runway. That is structural icing on contact, and it is one of the most dangerous routine weather codes for an aircraft on the ground or in the approach. Freezing rain often shows up when a small temperature-dewpoint spread sits near or below zero, which ties directly back to the temperature and dewpoint group. You will frequently see it written -FZRA for light freezing rain, and the FZ still means the same icing hazard regardless of intensity.

Read any weather group in seconds

The method never changes: split the group into intensity, descriptor, and phenomenon, then check the combination rules to confirm the reading. -RA is light rain, +TSGR is a heavy thunderstorm with hail, and FZRA is freezing rain with an icing hazard built into the FZ. When you would rather have it read for you, paste the raw report into wxdecoder and every present-weather group is expanded into plain English next to the original text. To see how a thunderstorm or freezing fog drives the bigger picture, read the flight categories next.

Last updated June 29, 2026