Quoted:You will now get an extended thread about NVIS
Don't let all the NVIS posts overcomplicate your understanding of this phenomenon. It's literally as simple as:
1. NVIS in the USA exists 99.9999% of the time on 40M, 60M, and 80M depending on time of day.
2. You can get a good idea of the f0F2 frequency (maximum usable frequency, or MUF) at the current time of day at the following website. There is plenty of historical data so you can see patterns and make predictions.
https://www.sws.bom.gov.au/HF_Systems/6/53. Choose the band that is closest to f0F2 without going over. Of course if that is 60M you won't get many contacts because it is not a popular band.
4. Put up ANY, literally ANY,
horizontally polarized antenna.
5. Put the antenna up
less than 1/4 wavelength above the ground (the default condition for any portable 40/60/80M antenna anyway).
5W is not a good performer on NVIS. 20W is a practical minimum, but you might make some contacts. This has to do with D and F layer absorption, particularly in the daytime.
Contacts will be within a few hundred miles.
All that said, there is never any harm in trying any band at any time. HF is like a box of chocolates. You never know what you are going to get when you make things very difficult (low antennas, low power, poor terrain). If you try hard enough and long enough you will make a contact. If you want to "cheat", don't forget to spot yourself on a POTA spotting website. And then you can be the guy that says "Shoot, man, you don't need that fancy amp and tower. Hell, I talked to Australia on 100 milliwatts and a lawn chair. And then I won the lottery. Hand me another beer, boy!"
If you want to get really crazy, consider balloon-borne or kite-borne antennas.