para abrir seu arquivo no notepad ++ automaticamente, apenas passe-o para o notepad ++:
"C:\Program Files (x86)\Notepad++\notepad++.exe" "D:\path of file\file.log"
Para que seja atualizada automaticamente, essa resposta já foi respondida na SU: Como recarregar automaticamente arquivos modificados no Notepad ++
Settings -> Preferences -> MISC -> Update silently
ou
There is a nice plugin called Document monitor (Can be found and installed from the Plugins => Plugin Manager => show Plugin Manager menu),
It updates the opened files every 3 seconds. Together with the option to "scroll to last line after update", it will have the ability to "tail" a log file as wanted.
After the plugin installation don't forget to activate it by clicking:
Plugins => Document monitor => start to monitor