Let's say I'm planning a day trip from a low elevation home base to a warm, mountainous location. I wake up early, check the weather, do performance calculations based on current METARs, and decide to make the trip. However, when I go to return home in the late afternoon, I find the elevation and the heat make the density altitude too high for me to take off.
Using purely FAA-approved weather sources, how could this be avoided? As far as I can find, there are no forecasts that include temperature or pressure. Several non-aviation weather sites provide an hourly forecast of both of those things. Is that the best way to avoid being stuck on the ground at a high density altitude? It's obviously no substitute for a standard weather briefing, but it seems to be a necessary part of "all available information."