The pressure field is symmetric. The highest pressure is in front of and behind the flow in the stagnation point region. The lowest pressure is at the top where the velocity is fastest. From the pressure field, we can see that separation is a likely possibility for a real fluid. Consider a left to right flow. For x<0, the value of the pressure is always decreasing, this is a "favorable" pressure gradient. If you were a fluid particle, you would feel more push behind than in front. For x>0, the pressure is increasing. The fluid encounters an "adverse" pressure gradient and the fluid is feeling more push in front than behind and this slowing down. If we remember that there is really drag caused by the solid surface, a fluid particle will not have enough momentum to get from the π/2 point back down to θ=0 (as it is expected to from the no drag case). Thus the fluid has no choice but to go off at some angle up to the right.