@verminal, this possibility is not available nowadays. This is on our to-do list.
Other weather apps have a more practical design - allowing the user to preselect their preferred weather model - which is then the source for both app and widget.
Windy, sadly, uses ECMWF as the default which then, unless ECMWF is your preferred model, has to be changed every time the user opens the app and renders the widget useless.
I note that Windy has just been updated. Metro Blue is now available as a model source.
I was hoping that the opportunity had been taken to synchronise the selected model to the widgets - as they are truly useless, unless ECMWF is your preferred model.
Also, once a model is selected it would be helpful to retain that model when the app is reopened. Rather than mine through the menu every time after closing the app.
Most, if not all, other apps synchronise with the widget and retain the selected model as the new default.