Hey everybody, I hope your Saturday is going well. Mine is. I haven't done much (or anything for that matter), but that's doesn't necessarily constitute a bad day. It's good to have a chill day every once in a while.
The story of this week has been the snow 173 miles to our south. Earlier this week, models showed Seattle getting some snow, but that has not been the case. Instead, Portland, Salem, Vancouver, and many other places in NW Oregon and SW Washington have been getting absolutely hammered with the white stuff. My uncle, who lives in Portland, came up to Seattle this weekend, and reports that there is over a foot of snow on the ground where he lives. This gives me mixed emotions... I'm happy for him and the kids of Portland, because I know how much joy snow brings and how it truly lifts the spirit on even the darkest day, but I'm also extremely jealous of their situation.
But not all is lost, as we may get some snow tonight. The National Weather Service is predicting an inch or less in the Seattle metro area, and they are initially basing this on pressure gradients between certain stations to our north and south. For example, if there is much higher pressure over at Bellingham than Olympia, the winds will howl southward, but if the pressure is much lower over Bellingham, a strong wind headed to the north will dominate, as wind at the surface always flows from high pressure to low pressure (unless something REALLY screwy is going on and messes with the sum of force vectors that end up creating the wind vector). At 3 p.m., the pressure gradient between Seattle and Yakima was -9mb (meaning Yakima is higher) and the Olympia to Bellingham gradient was -4mb (Bellingham is higher). This corresponds to dry, northeasterly flow, which, while cooling our air, could decrease the amount of precipitation we will receive. Hence, the National Weather Service is only giving Seattle an inch of snow... tops. Places to the south, Olympia and south of there, are expected to pick up 1-3 inches of snow. Meanwhile, the NWS office in Portland is still giving the Portland metro area a Winter Storm Warning for 4-6 inches of additional snow. -_-
Looking at the radar, it looks like the Seattle area will see more than a measly inch. We've got a lot of greens headed up our way.
|UW Radar - http://www.atmos.washington.edu/weather/radar.shtml|
But here's the problem. Much of this precipitation is not reaching the ground. Why? The air mass is too dry! The moisture simply evaporates before it can hit the ground. As more precipitation evaporates, the air gets more moist, and it also gets cooler due to a process known as evaporative cooling, which I won't go into depth here. But if the precipitation rates are too light, all of the moisture will evaporate before reaching anybody, and we won't see any snow, even though it is indeed snowing up above.
I think that Seattle will be lucky to make it to the 1-inch mark. Hopefully we can get a few flakes for some nice scenery. The air is just too dry and I don't think the heavier moisture is going to get up here. Places like Olympia and Centralia, though, have a much better chance of picking up 1-3 inches or even more, and I think they will actually get more than the NWS is predicting.
I don't have access to atmospheric moisture content like the NWS guys do, so this is a hard prediction for me to make. Nevertheless, I'm fairly confident that we'll see some flakes and perhaps a little bit of accumulation here in Seattle, but nothing to take a second look at. I'll post updates all night long as warranted.
***NOTE: A SNOW ADVISORY WAS JUST POSTED FOR PIERCE COUNTY, EXPANDING NORTHWARD ON THE ONE FROM THURSTON AND COUNTIES SOUTHWARD. I STILL THINK SEATTLE WILL LARGELY STAY BELOW AN INCH, BUT WOULD HAPPILY BE PROVEN WRONG.