Definition
In a METAR, a qualifier is a code letter placed before a weather phenomenon to describe its intensity or proximity. The three qualifiers are minus (-) for light, plus (+) for heavy, and VC for in the vicinity of the airport (between 5 and 10 statute miles from the point of observation). No symbol indicates moderate intensity.
Plain English
A small code in front of a weather type that tells you how strong it is or whether it is near the airport rather than at it. A minus sign means light, a plus sign means heavy, nothing means moderate, and VC means it is happening close by but not on the field.
Context Anchor
Seen in the present weather section of an aviation routine weather report, especially when reading METAR weather codes before a flight.
Derivation
From Latin qualis, meaning 'of what kind.' A qualifier is something that tells you what kind or degree of a thing you are dealing with. In a METAR, it tells you what kind of rain, snow, or other weather is being reported -- light, moderate, heavy, or nearby.
Why Pilots Care
Tells pilots at a glance whether conditions are light, heavy, or nearby so they can judge flight safety and planning.
Intuition Check
Do not read qualifier as a general label or a pilot qualification. In a METAR, a qualifier is a specific weather-code part that modifies the reported weather condition.
Example Sentence 1
The METAR showed -SN, so the pilot knew light snow was falling at the field.
Example Sentence 2
VC in the qualifier meant the fog was in the vicinity but not overhead.