In the Tropics, we talk a lot about "coupling" between the ocean and the atmosphere.  That is, ocean temperatures often drive the atmosphere and, vice versa, the atmosphere helps to force the ocean.  This forms the basis for ENSO.  

However, in the Extratropics (or higher latitudes that are farther away from the Tropics) this coupling is much weaker and one way.  This is because the physics in the Extratropics are different than in the Tropics.  In the Extratropics, like the North Pacific Ocean where "the blob" resides, the ocean temperatures are often caused (or driven) by the overlying atmospheric circulation and wind patterns.  But the opposite is often not the case -- *especially* on seasonal timescales.  That is, the North Pacific Ocean temperatures ("the Blob") is not the main culprit for the large-scale circulation/wind patterns that lie above it.  Quite often, especially over the North Pacific and North America, it is changes in the *Tropics* that drive the atmospheric circulation that influences the Pacific Northwest (PNW).  

So, in making the forecast for the Pacific Northwest for the coming winter, forecasters will likely be much more concerned with the state of El Nino than in the state of the Blob.  The Blob can have more local impacts (warmer conditions right by the coast), but it is not expected to have a big impact on the larger scale circulation.