Use raster memory layer from QGIS processing result

I want to apply subsequent QGIS raster processing algorithms in a python script. I want to use memory layers for intermediate calculation results since I am only interested in the end result.

As described in a previous post, for vector layers this works fine when run in the Python console:

processing.runandload("qgis:intersection", layer1, layer2, "memory:myLayerName")

I can access the "memory:myLayerName" for subsequent calculations.

I'd expect a similar syntax for rasters, but I can't get this (or other functions where a raster is created as an output) to work:

processing.runandload("gdalogr:cliprasterbymasklayer", path_to_raster,
                      path_to_shape, "", False, False, "", "memory:OutputRaster")

I get an "Oooops! The following output layers could not be open" - error. The processing.log file shows:

'INFO|Sun Mar 01 2015 02:20:52|GDAL execution console output|ERROR 1:
TIFFOpen:memory:temp_layer: Permission denied'

When I replace the "memory:OutputRaster" with r"C:/path/to/out/raster.tif" the code runs. What am I doing wrong?