Jeff's Sound to Summit Forecast

The Good, The Bad, The Semi-Ugly

Saturday, June 20, 2009

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Summer may officially begin late Saturday evening, but it won�t feel like it. But then we�ve been spoiled for the last month. This weekend, our record-tying dry spell will be but a distant memory, with early-spring-like conditions in the mountains, together with some moderately challenging conditions on the water..

THE BIG PICTURE:

The split in the jet stream that sent clouds everywhere but western Washington is no more. Even a cursory look at satellite images show clouds racing across the Pacific Ocean toward us! Still, there�s a bit of a break, and that means decreasing showers later Friday evening into Saturday as surface air pressure rises. However the break may not last long. And the cool air rushing in behind it will drive snow levels down in the mountains Saturday. More on that below.

Much of the action will be rooted in the upper atmosphere; a low will slide over British Columbia�s Queen Charlotte Islands Saturday. A disturbance extending south of that low will move into the coast Saturday evening, slowly stretching south and sliding into the Sound and Cascades by about mid-day Sunday. That will increase the potential for showers, especially over or near the mountains. But because the disturbance will stretch southward as it approaches our area, it is likely to weaken. That�s good news.

Special Boating Weather Remarks: Much of western Washington will still wake up to low morning clouds Saturday, but some clearing is likely in the afternoon. Sunday, the approach of that disturbance I mentioned above should increase cloud cover.

Winds don�t look terribly impressive Saturday, with the possible exception of the Strait of Juan de Fuca in the afternoon hours. Winds could reach 25 knots there, largely in the central to eastern Strait. Otherwise, expect more modest winds; probably 10 to 15 from the northwest along the coast albeit with swell reaching 7 feet. Puget Sound will struggle to find wind in the morning, but rising to perhaps 10 to 15 knots in the afternoon (probably closer to 10 knots). The San Juans and Bellingham bay may begin a bit breezy (perhaps 15 to 20 mph) but slowly ease in the afternoon hours Saturday, as winds back from northwesterly to southwesterly.

Sunday, winds will rise in most areas; the coast will likely see 10 to 20 and possibly even 25 knots in the afternoon. Similar winds are likely in the Strait, San Juans and Bellingham Bay (though more in the 10 to 20 knot range). The one exception: Puget Sound. We�ll be lucky to reach 10 knots Sunday, and winds will be fluky-a sailors� nightmare. Of course, keep an eye on my colleague�s updated forecasts on television or here on www.king5.com if you have access to either, or tune into NOAA weather radio if you�re out on the water.

Special Mountain Weather Remarks
Although Saturday looks like the drier of the two days, the moderately strong onshore flow will produce uplift along the Olympics and Cascades; the rising air will maintain at least a potential for showers, something we call orographic enhancement. Any showers that do form will produce snow at relatively low levels-certainly not what climbers typically expect for the first weekend of summer�even if it�s the first partial weekend of the new season. Some sunbreaks are possible, but I believe skies will generally be mostly cloudy over the mountains this weekend. The potential for showers will increase Sunday with the arrival of that trough of low pressure.

Saturday
Snow Level: 5,500 to 6,000 feet
Pass Highs/Ridgetop Highs/10,000 foot Highs
48 to 56 degrees/42 to 47 degrees/23 to 27 degrees
Pass Winds/6,000' Winds/10,000' Winds
Northwest 10 to 15 mph/Northwest 10 to 15 mph/Southwest 5 to 10 mph

Sunday
Snow Level: 5,000 to 6,500 feet
Pass Highs/Ridgetop Highs/10,000 foot Highs
47 to 54 degrees/40 to 47 degrees/20 to 25 degrees
Pass Winds/6,000' Winds/10,000' Winds
Northwest 10 to 15 mph/Northwest 15 to 25 mph/Northwest 5 to 10 mph

Have a good weekend!

Jeff Renner is the Chief Meteorologist for KING 5 News, and the author of Mountain Weather and Lightning Strikes on thunderstorm safety, all published by Mountaineers Books, aimed at making sure you don't find yourself staying at home, wishing you were enjoying a beautiful day in the mountains or on the Sound, or hunkered down in a storm desperately wishing you were at home.