Howie wrote:
making in effect a huge soft box that lights the subject
Nicely put!
Here in southern Ontario, morning light means a combination of warm colour temp., low sun angle so long shadows, and often atmospheric moisture/haze.
The light colour can be approximated simply by moving a slider in your raw converter to a warmer hue. Paintshop Pro even provides a colour temp. slider for JPEGs. In either case you're adding a yellow-orange cast.
The haze might conceivably be faked by opening Levels and moving the black point in
Output Levels a bit to the right. Then by duplicating background layer, adding a slight Gaussian blur, changing the new layer's opacity to 50% and its blend mode to Luminosity.
For the shadows you're on your own... ;)
