They called their collection of log buildings, Fort Clatsop, and remained there until late March 1806 (see artist rendering).
Unfortunately, they learned rapidly that they had picked one of wettest, dampest lowland places in North America, with plenty of wind to make things even more unpleasant They were miserable, as their comments on December 16, 1805 made clear: "The rain continues, with Tremendious gusts of wind. The winds violent. Trees falling in every direction, whorl winds, with gusts of rain. Hail & Thunder, This kind of weather lasted all day, Certainly one of the worst days that ever was!"
Frequent comments included: "we are all wet and disagreeable," "cold and a dreadful day," and, "the rain continued as usual"
If only they had a meteorologist with them! Consider the Oregon annual rainfall map (see image). They had camped in a location that receives about 100 inches a year, most of it falling during the midwinter period in which they camped. Not a good choice. If only they had made camp near Portland, they could have found a location with roughly a third as much rain, and considerably less wind.
Of the 106 days the Corps of Discovery spent on the coast only twelve were free of rain and only six were sunny. I suspect they knew they had picked a very wet location, but wanted to be near the ocean where they would have a chance to interact with a passing ship. Perhaps they hoped for a ride to Hawaii.And one more thing: only a few miles from Fort Clatsop there is Cape Disappointment, the foggiest location in the lower 48 states, with 106 days of heavy fog a year. So they were wet, fogged in, and we haven't have talked about the strong winter winds of the area. Not your winter vacation spot.
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| Typical (foggy) conditions at Cape Disappointment |
The purple colors are the heaviest snow on the map, virtually all of it over the mountains of the Pacific Northwest and southern B.C. Yes, I have to give credit to our neighbors to the north (but that is a short drive for us anyway).
To show you this, here are the snow forecasts for the next two 72 h periods from the UW WRF model forecasts. For the next few days the Sierra and Siskiyou Mts. will get hammered with many feet of snow (yards in some places). We will slowly enhance our snowpack and BC/norther Rockies will get substantial amounts.
For the second 72 hour period the snow accumulation is more evenly distributed up and down the coast, with over a foot of snow enjoyed by all. Eastern Washington and Oregon get plenty.
All and all, a nice Holiday gift for those who enjoy winter recreation, and the amounts should not be heavy enough to mess up the roads.
Strong southeasterly flow will be forced to rise up over the Olympic Mountains--in fact the lift starts tens of kilometers upwind of the Olympics. Thus, there will be heavier precipitation over Mason and Kitsap counties. 
In marginal situations, places with less precipitation (like Seattle in this case) will be mainly rain (perhaps a few wet snow flakes mixed in on the hills), but areas with heavier precipitation rapidly turn to snow as melting of snow falling from aloft progressively cools the air air, pushing the snow level down to the surface. (heavier winter precipitation around here virtually always starts as snow aloft).
But what about Seattle? Here is the same type of plot at the same time. The air is saturated (temperature and red lines are not on top of each other) and the air temperature is above freezing for a few thousand feet above the surface. Rain and disappointed kids.
The next day, with warmer air, the snow is over over the west, but large parts of easterly Washington, including around Spokane and Wenatchee should be whitened up.
Here is the predicted snow for the next 72 hr. The Cascades will get plenty, particularly over the southern sections (e.g., Crystal, Mt. Hood!). 
Do we have a chance of any records? The greatest annual rainfall at Sea-Tac was 55.14 inches in 1950. There is little chance we can reach that in a few days. Only three years (including 1950) got above fifty inches...there is a good chance we will get close to that level. In any case, we will "enjoy" living in one of the top 10 wettest years since 1948. 
The European Center Model has very little precipitation over the lowlands during the next week, and even the U.S. GFS model takes most of it to the north and south of us. This weekend looks fine, with only a few showers around. No serious weather.
The maximum winds (gusts) for the 24 h ending 5 AM for Washington and Oregon are shown below. The Oregon coast got hammered with lots of places getting 50-60 mph winds, some more. Some 40-50 mph gusts in the Willamette valley.
For Washington, 60 mph+ along the coast, with 40-60 mph in the Strait. 40-50 mph gusts in southern Puget Sound, with higher winds (up to around 60 mph) in the southern Sound.
The biggest storm of the season so far (and I haven't even talked about snow in the mountains), but typical of the strongest storm we get each year.