No doubt about it. We can't see them today with the heavy overcast but on any other day when there are winds of about 25 knots at about 12,000 I tend not to fly over the Sierra just for that reason. Of course, when I take the 4,000 HP Cessna 172 with full after burner it isn't a problem
So far I'm just hearing reports of turbulence and icing but nothing much about wind shear (yet).
This is a good day to pull up MS Flight Sim with real-world weather and do some "what if" flying.