In that loop, you can see the full evolution of this dry spot.
A glance at the surface map (from our WRF-GFS model analysis this morning) shows no apparent surface low, though there is a trough of lower pressure at the surface in the vicinity. In the map below, the dry spot is located in the area between the two high pressure centers--one off the coast of the Pacific Northwest and the other in the central Pacific.
So this is not a feature that means much for the surface. However, looking at the 500mb chart we do indeed see a little cut-off low analyzed in the location of that dry spot. Overlaid on the image in color is the relative humidity at 500mb. Red indicates high relative humidity (very moist air) whereas blue indicates low relative humidity (very dry air). I personally would have reversed the color scale, but it is what it is. Anyhow, you can see that in the center of the 500mb low, it is indeed very dry. There is also an area of more moisture shown just to the east and south of the low center, and on this morning's water vapor imagery we also see the same thing.