Mountain Weather Forecast

Weather Synopsis

With the jet stream directing the storm track into California, the PNW sits in an unseasonably cold unstable air mass with a broad upper level trough overhead. We'll see the trough steer showers inland throughout the weekend.  Upper level disturbances emanating from the upper trough will enhance shower activity at times. A cluster of showers associated with one of these upper level shortwave features is rotating north through Washington State this afternoon with more scattered showers to the south.  We'll see a quieter period this evening unitl another shortwave lifts north late tonight through Saturday morning, spreading renewed showers on both sides of the crest. There will also be an uptick in E-SE ridgeline winds in most area.  The Olympics will pick up the most snow in this pattern, but all areas will squeeze several inches of low density snow out of an otherwise unimpressive precipitation forecast.  

By Saturday afternoon, the flow aloft becomes SW and we'll see more scattered showers associated with daytime heating and a cold unstable air mass. W-SW ridgeline winds will become Saturday afternoon except where they're locally strong near Mt Hood. Showers should wane Saturday night, and spark up to a lesser degree on Sunday as the upper level trough begins to weaken. 

We may see a similar pattern on Monday with showers that wax and wane with daytime heating in SW flow.  However, a developing frontal system approaching from the SW may impact the Mt Hood area and perhaps the south WA Cascades, or heavier precipitation may stay further south.  Throughout this period, snow levels will dip overnight near sea level, and only rebound to 1000-2000' during the day. Temperatures will cool rapidly with elevation with overnight lows in the teens and highs in the low to mid 20s at 5000'.  Freezing levels during drier periods and longer stretches of sunshine will be roughly 500-1000' higher than the snow level during showers.