Time and Day:  0545 Friday

The Snapshot:   Light to moderate snow with gusty winds today, light snow and cooler temperatures Saturday.

Current Observations:  The mid-mountain inversion is still present with 34 degrees at the upper sites and 23 degrees in the base area. However, winds at pass level are calm and there is no fog! Upper mountain winds are light and from the west. RH is 92 in the base area (62 at 4850’) and the barometer is dropping steadily.

The Science:   The much anticipated change in our weather pattern is taking shape this morning. Cold air remains pooled east of the pass, maintaining the inversion for the moment, but upper level temperatures have dropped and a trough with associated cold front are approaching our area. Precipitation has already begun in the Puget Sound/north interior and should spread from north to south this morning. Freezing levels will drop nicely with the frontal passage, along with an increase in winds and a brief period of moderate snow. The front is relatively weak, and only light snow showers will continue Friday. Upper level flow becomes WNW bringing continued light snow showers at cool temperatures Saturday.

The Long Range: Upper level flow strengthens on Sunday, becoming zonal (broadly from the west) with a parent low in the Gulf of Alaska and plenty of moisture. Freezing levels will bump up a bit Sunday midday, bringing snow levels to Pass elevation. Moderate to heavy snow is expected Sunday and Sunday night before drying out for a bit Monday, with cooling temperatures. Currently Tuesday/Wednesday looks very interesting, with heavy snow in the mountains and high winds in the Puget Sound possible. 

24hr Precipitation ending at 4am: Today 24hr water: .5    Snow: 4-6” Tomorrow’s 24hr water: .25    Snow: 2-4” Trend and Timing: Light snow will start after daybreak Friday, becoming moderate mid-morning before turning to light snow showers Friday afternoon and evening. A brief period of convergence showers may take place before sunrise Saturday.

24hr temperature ending at 4am:  Low: 22 High: 34 Free air freezing level: 5,000’-1,500’ Trend and Timing:    Rapid cooling during the day Friday and overnight, remaining cool Saturday.

24hr Winds (mph) ending at 4am: Base: W 10-15 Ridge Top: W then WNW 15-25 Trend and Timing: A period of gusty winds will occur with the frontal passage Friday mid-morning, then become steady from the WNW thru Saturday morning. DV