MOUNTAIN WEATHER FORECAST

0900 Friday:

The Snapshot:  And So It Begins.  Today there will be strong winds, heavy snow and a touch of rain.   Snow showers persist tomorrow, then hit repeat on Sunday for high winds and more heavy snow.   

The Science: A triple point frontal system approaching the PNW will bring heavy precipitation and wind to the Cascade Mountains today.  The first warm front will spike freezing levels to 5000’ as it passes over.  The rise in temperature will be short lived with a strong cold front quickly following.  Thus, expect a short (1-2hr) period of rain below 4500’ sometime late this afternoon.  Freezing levels will drop to 4000’ in the wake of the cold front.  High westerly winds and the development of the Puget Sound Convergence Zone will enhance snow fall through the early morning hours. The occluded front will move through early tomorrow morning which will mark the end of the first wave of precipitation.   Snow showers continue tomorrow as cooler unstable air fills in behind the frontal system.  Another frontal system arrives on Sunday with more wet and heavy snow.       

4-7day Long Range:  Long range models are quickly changing for what will happen after the weekend –so confidence is low.  As of now, Monday will start out dry with moderate precipitation and rising freezing levels starting later in the day.   Heavy rain Monday- Wednesday is possible.  Hopefully, that will change.  +- 8000’ freezing levels are still forecasted on Wednesday with significant cooling by the end of the week.      

24hr precipitation ending at 4am tomorrow: Water =.75-1   Snow = 8-12” Storm totals by 4am Monday morning = 18-30” of snow. Trend and Timing: Light precipitation is now falling in the mountains with the main front over Puget Sound.  Snow at first with a 1-2hr period of rain this afternoon changing back to snow later tonight.  Convergence development will enhance snow fall around midnight.   Snow decreases in intensity early tomorrow morning but will continue.

24hr temperature ending at 4am tomorrow:  Low: 30   High: 36 Freezing level: 5000’    3800’ Freezing Level Trends and Timing Freezing levels will spike to 5000’ this afternoon.  Once the cold front moves through the freezing levels will fall to 4000’ or slightly lower.   East flow will play a part in the surface temperatures until the cold front moves through later today.

24hr Winds (mph) ending at 4am tomorrow: Base: 0-5 E shifting W Ridge Top: 0-10 E, shifting W, strengthening.    Trend and Timing: Easterly winds will hold until early this evening.  Strong westerly convergent winds will fill in behind the cold front this evening (7-10pm).  40 knot winds will be possible through most of the day tomorrow.