Mountain Weather Forecast

Time and Day: 0700 Saturday

The Snapshot: Cool and intermittently foggy in the base area, sunny and warm on the upper mountain today. Increasing clouds and light snow tomorrow.

The Science: Satellite imagery this morning shows a triple point frontal system with a parent low centered in SE Alaska and a long SW-oriented fetch of moisture aimed at the Northern Coastal Range in BC. They will experience extreme winds and high freezing levels. Fortunately it is well off shore of Washington and the main effect felt in the Cascades should be scattered clouds. A high pressure ridge is in place over Washington, providing high freezing levels, mostly sunny skies, and dry conditions throughout most of Washington and Oregon. An exception is the base area at Stevens Pass, where an inversion and light east flow is bringing below freezing temperatures and intermittent fog. Above mid-mountain (~4500’) it is above freezing and should be partly sunny today.

The ridge flattens a bit Sunday, allowing more westerly upper level flow to clip the northern part of the state. A very weak embedded trough should move across Northern Washington Sunday night.

The Long Range: Monday looks mostly dry and partly cloudy, with lower freezing levels (~2,000). A feature called a Rex Block looks to develop on Tuesday. Typically these features are not helpful to Western Washington in terms of snowfall. However, this one looks to set up just far enough west that the convergent flow on the eastern side of it (similar in concept to a Puget Sound Convergence Zone) may lead to enhanced precipitation (snowfall) for the Cascades next week. Stay tuned for details. 

Precipitation Ending at 4am: Today 24hr water = 0  Snow = 0 Tomorrow’s 24hr water = >.25 Snow = 1-3” Trend and Timing: Precipitation should arrive late Sunday afternoon, a brief shot of snow will end by midnight.

24hr temperature ending at 4 am tomorrow:                                        Low: 22 (in base area)    High: 40 (on upper mountain) Freezing level: 7,000 Trend and Timing:    Freezing levels should peak Saturday night before slowly falling back to near Pass level during the day Sunday.

24hr Winds (mph) ending at 4 am tomorrow: Base: E 5-10 Ridge Top: Variable 5-10 Trend and Timing:  East winds should hang in there through Sunday morning. The battle of East vs. West should be in place at the ridgetops, with temperatures swinging back and forth accordingly. DV