A full latitude trough at 500 hPa over Western North America featuring embedded short wave troughs over British Columbia and Washington, is a favorable set up for heavy snowfall in the Seattle and Portland areas. In January 1950, this 500 hPa pattern coupled with increased baroclinicity due to a cold surge at 850 hPa over British Columbia resulted in a heavy snowfall event west of the Cascades. This event was the heaviest snowfall on record for Portland, Oregon. Notice the significant standard deviation from normal for 850 hPa temperatures just north of the heavy snowfall area.