The flags are optional, and the mention of that is subtle, but it's there.

Just use:

*Timer Name 1000 !alert started

That would be called with "!timerstart Name"
In 1 second (1000ms - default, since no s/m/h is defined) !alert would popup with "started" as the text.

The "weather" in Dev's is a group option. The "timeout" in deuce's example is probably wrong syntax :) but would be translated in to a group.

edit -

Just so there's no mistake, what you would want is:

*Timer SleepTimer 2s !Amp_Pause

(Changing the 2s to whatever time you want, of course, like 30m.)