The catch phrase within the US FARs is "weather reports, forecasts, or any combination thereof".
Excerpt from FAA Order 8900.1, Flight Standards Information Management System:
3-2049. POLICY ON CONDITIONAL PHRASES IN REMARKS PORTION OF
WEATHER FORECAST.
A. Weather forecasts provided by the National Weather Service (NWS) and other
sources often have conditional phrases such as “occasional,” “intermittently,” “chance of,” or
“tempo” in the remarks portions of the forecasts. These phrases supplement the main body of the
forecast by indicating the probability of changing conditions during the forecast period. These
modifying phrases, used in the remarks portion of a terminal forecast (FT), indicate the weather
conditions for an area within five nautical miles of a runway complex. Certain regulations
concerning the selection of destination and alternate airports require that “weather reports or
forecasts, or any combination thereof, indicate that the weather conditions will be at or above...”
the minimum weather conditions specified in those regulations. The FAA Office of Chief
Counsel has consistently interpreted these regulations to mean that the worst weather condition
in any of the reports or forecasts used to control a flight movement is the controlling factor.
These interpretations make the remarks portion of a forecast as operationally significant as the
main body of the forecast. Therefore, it is FAA policy that the worst weather condition in the
main body or the remarks portion of a terminal forecast, as well as any weather report used, is
the controlling factor when selecting a destination or alternate airport.
All due respect to the instructor, this has been around for years...it was in 8400.10, the Air Carrier Inspector's Handbook, before that document was rolled into this new one. You can dig this up on the web.
Indeed, there are actually ATA exemptions designed to end run this.