MOUNTAIN WEATHER FORECAST

Time and Day: 0700 Sunday

The Snapshot:   Partly cloudy today with stormy conditions developing this afternoon. Moderate to heavy rain and snow overnight and clearing Monday.

The Science: The frontal boundary for the next round of weather is rapidly approaching the coast this morning. Clouds will increase throughout the day with precipitation starting after noon. Freezing levels will rise above pass level as the front approaches, providing a period of potentially “mixed precip” Sunday afternoon. A relatively cooler air mass follows the front, bringing freezing levels back down after midnight and Monday morning. The event should end with snow all the way to the base area at Stevens Pass. The atmosphere quickly dries out Monday morning, with brief ridging in advance of the Big Event. Monday should be mostly dry, partly cloudy, and benign.

The Long Range:    A classic southerly flow atmospheric river event is setting up for the Tuesday through Thursday period. This has been well advertised for several days and seems to be on track. Freezing levels in the 8-9,000’ range can be expected with several inches of rain across Washington. The Olympics and volcanoes will see the most precipitation, with ~8+” of water likely. Stevens Pass is often somewhat blocked in this pattern, but will see several inches of rain by Thanksgiving regardless. The good news is that the snow we’ve received so far this year is quite dense and well consolidated; we should still have something to slide on by the end of the week.

24hr Precipitation ending at 4am: Today 24hr water = .75-1.0   snow = 4-6” in base area, 6-8” on upper mountain Tomorrow’s 24hr water = .25  snow = 1-3” Trend and Timing: Precip should start as light snow after noon today, then become a rain/snow mix this afternoon and evening before finishing with a shot of snow. Day 2 snow amounts will be early Monday morning.

24hr temperature ending at 4am:  Low:  26   High: 35 Snow  level: 3k – 5k – 3500’ Trend and Timing:    Snow level should rise this afternoon then fall after midnight to below pass level through Monday morning.

24hr Winds (mph) ending at 4am: Base: 5-15 W Ridge Top: 20-30 SSW Trend and Timing: Winds will increase this afternoon and be gusty overnight and Monday morning. DV