Regular Expressions 101

Explanation
Pro

\ban ASCII word boundary

Group 1(\d{4})

\d{4}a digit, repeated exactly 4 times

Non-Capturing Group(?:\b|[A-Z]{3})

1st Alternative\b

\ban ASCII word boundary

2nd Alternative[A-Z]{3}

Character Class[A-Z]{3}

{3}matches exactly 3 characters from the set below:

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

Detailed match information will be displayed here automatically.

25 tokens

\b(\d{4})(?:\b|[A-Z]{3})

New

281320Z 26015KT 9999 3333 4444 FEW028 SCT033 BKN053 16/10 Q1007=
281320Z 26015KT 9999ABC 3333ABC 4444ABC FEW028 SCT033 BKN053 16/10 Q1007=