When looking at gradients in the Gorge, we often look for a thermal low, connected to the Great Basin, which often sits in the Columbia Plateau most of the summer.  But in Spring, when upper level lows are present, a surface low pressure gets created out ahead, under the highest Differential Potential Vorticity Advection (DPVA).  The DPVA creates rising air,  and

pressure field

underneath the rising air, you get low pressure at the surface.  When low pressure is present out east, and the North Pacific High is strong and close to the Coast, pressure gradients occur, like today!  Check out these pressure fields today!