Why do we often get northeast winds even though the jet stream blows from the west?

Dear Tom,
Why do we often get northeast winds even though the jet stream blows from the west?

Lisa,
Oak Park

Dear Lisa,
A more general statement of your question is, “Why does the wind that I experience not always blow from the same direction as jet-stream winds?” Jet streams are relatively narrow air currents blowing often at speeds of 70-120 mph (or stronger), usually from a westerly (west, northwest or southwest) direction and usually above 25,000 feet. The truth, however, is that wind direction varies with height and rarely blows from the same direction at all elevations. The forces that determine the direction of jet-stream winds become weak or non-existent at ground level, and surface winds are the result many factors (like terrain variations) that do not exist aloft.