Mountain Weather Forecast

Time and Day: 1200 Sunday

The Snapshot:  A surprise 14” of cold smoke overnight, and a beautiful clear morning. Light showers ending today and clear and cold conditions going into the New Year.

The Science:  Yesterday’s SWE (snow-water equivalent) forecast was pretty close, but when it snows at 15 degrees the same amount of water goes a long way. A warm parcel of air can hold more water vapor than a relatively colder parcel of air, so when the same amount of water goes into colder air, the result is lower density snow and therefore higher total amounts of snow. We’ll take it.

Stationary low pressure centered over the OR/WA border and a large high pressure ridge in the Pacific will usher very cold arctic air into the Pacific Northwest over the next few days. The upstream airmass moving into our area will be continental in origin so no moisture is expected for the next few days. Surface temperatures will be very cold. East winds will also pick up the next few days, bringing dangerously low wind chill values.

The Long Range: Model agreement is poor beyond Wednesday, thus confidence is low in the 5-7 day range. The GFS has west/northwest flow developing with precip, the European is drier into the weekend. These details should resolve by mid-week.

Precipitation Ending at 4am: Today 24hr water = >.10 Snow = 0-2” Tomorrow’s 24hr water = 0 snow = 0 Trend and Timing: Light showers should end mid-Sunday, with no moisture expected Monday.

24hr temperature ending at 4 am tomorrow:                                        Low: 6    High: 20 Freezing level: Surface Trend and Timing:    Stevens Pass should be seeing it’s high temperature for the day around noon-2pm, with temperatures dropping overnight and remaining low Monday morning.

24hr Winds (mph) ending at 4 am tomorrow: Base: E 20-30 Ridge Top: ENE 20 Trend and Timing:  East winds are in place currently and should strengthen during the day Sunday, becoming moderate to strong and gusty Sunday night and Monday. DV