I'm wondering if Sun Peaks would appeal to a Seattle intermediate? These people are used to skiing the Cascades. I would think they would be unimpressed with the terrain and amount of snow fall.*
The WA Cascades are not that great for intermediate skiers. It can rain at the summit of most mountains 1-3x per winter and more frequently at the bases. Sun Peaks and Big White, with slopeside condos, good terrain, driveable, and fewer crowds than Whistler, are quite appealing.
Snoqualmie Pass/Alpental - 1 or 2 sectors, but generally too mellow (West side) or too tough (Alpental). Very Wet Snow! Prone to rain. 3k base elevation.
Crystal - It's not that great for intermediates. It's either too steep/crowded or a bit flat—just 1 or 2 sectors.
Stevens Pass - Best intermediate area. There are a few lifts with cruisers on the front or back sides. Also, due to the pressure gradient, cold air gets sucked through Stevens Pass from the interior, keeping the snow quality better.
However, if you are looking for a long weekend, you can go to Whistler, Interior BC, Mt. Bachelor, or you may have to hop on a plane. The Okanagan is thought to have 'drier' snow vs. Western Cascades - similar to how Mt. Bachelor has better snow quality than the Mt. Hood areas.
Believe it or not, the area that advertised the heaviest around Seattle is Sun Valley - the GOT SUN? campaign (billboards). Similar to the GOT MILK? campaign. Seattleites suffer from low light syndrome, so they are more than happy to go to sunny Idaho with low snow for some Vitamin D. Also, there is a very strong historical connection between Seattle and Sun Valley - lots of 2nd homes there, same ski shop chains, drivable for a week, etc. Hence, the name of one of the most popular Sun Valley sectors is Seattle Ridge.
Frankly, Seattleites think Colorado or Utah is a ski vacation. Casual NW skiers will complain that they got rained out/fogged out at Whistler since they generally only use the middle 1/3 and a few runs from the top.
Or they will go to Mexico, Palm Springs, Hawaii, etc. Anything to get out of the NW for a few days during the winter.
They have excellent local skiing, but heavy Cascade snow is tempered by occasional rain, wet snow, fog, clouds, etc.
In general, you will find a lot of American skiers (especially casual skiers) who tried Whistler and will never go back because there was no sun for a week or got a Pineapple Express (warm) storm where it rained to the summit, etc. Hence, there are no real destination ski resorts in the NW USA (maybe Mt. Bachelor).