How funny. After lying dormant for 18 months, this thread is off and racing! Maybe only TEMPOrary!!
:hmm:

....a whole thread on what should be simple. Representative of an industry that cannot fathom the complicated speak inflicted by lawyers. Part 61 etc adds to this. We have an industry running on guesses.

As simple as.......

Even includes a little memory jogger to help you out.No wonder things are safer over there.

IFR Alternate Airports (1-2-3 Rule).

When filing an IFR flight plan, you must include an alternate destination airport when the weather forecast at your original destination predicts conditions below those specified in CFR 91.169. To help remember those conditions, you can use the 1-2-3 rule.

1 - During the time 1 hour before to 1 hour after the estimated arrival time
2 - Ceiling less than 2,000 feet
3 - Visibility less than 3 miles

If the above conditions exist, an alternate airport must be filed.