Wednesday, January 8, 2013
9:37 p.m.
I’ve been waiting for this date for so long!
 |
| Franklin Falls Webcam on I-90: http://www.wsdot.com/traffic/passes/snoqualmie/default.aspx |
Snow in the mountains. But not only that… snow at Snoqualmie Pass. I’m taking a class with Cliff Mass this quarter, and he’s a bit skeptical that the Summit at Snoqualmie will get enough snow to open next week, but he is certain that they will get more than they have than a while.
I am certain that ski operations will begin at the Summit next week. Well, I am certain that they will have enough snow that they should. I don’t know the inner workings of Boyne USA.
I’ve reposted the diagram I had yesterday of the SNOTEL snow-water-equivalent (SWE) percent of normal for the Western U.S. Percentages are well below average in Washington, and Oregon and California are nearly completely barren. We’ll see how this has changed once this storm cycle is over.
 |
| http://www.wcc.nrcs.usda.gov/gis/snow.html |
How can I be so certain that we will see such heavy snowfall amounts? Well, first off, we have some pretty powerful systems entering the area. We’ve already seen some fairly sizable rainfall totals… yesterday we picked up 0.48 inches at Sea-Tac, and today we have 0.38 with two hours to go (our precipitation is mostly over). Snoqualmie Pass, at an elevation of 3,022 feet, has had 9 inches of snow measured at 3,010 feet in the last 24 hours, as strong orographic enhancement has kept the snow falling there all day.
Another weak system will arrive on Thursday and should bring another half foot or so of snow to the passes, but the big story is Friday, as a degrading 970 millibar low makes landfall on the northern tip of Vancouver Island. Associated with this system will be a strong warm front, which will initially give us rain both here in the lowlands and in the mountains save the highest elevations, but after this warm front passes through, we will be under the influence of a cold front, and this will continue to bring rain to the lowlands but will bring snow to the mountains. One thing is for sure… this system will bring a LOT of precipitation all around.
 |
| Valid 04:00 pm PST, Sat 11 Jan 2014 – 72hr Fcst: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d3_wa_pcp24+///3 |
And how about the snow? You’re gonna like this…
 |
| Valid 04:00 am PST, Sun 12 Jan 2014 – 84hr Fcst: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d3_wa_snow48+///:3 |
This model shows two feet in two days at Snoqualmie, and I’ve generally found that these mesoscale models tend to underestimate the snow directly at Snoqualmie Pass. See those whites in there? Those represent over four feet of snow in two days. Wow.
But we aren’t done yet!
I’m going to have you look at the upper-air chart, because I think it is important that you understand why the Cascades will get a lot of snow even after all the systems have gone through.
 |
| Valid 04:00 am PST, Sun 12 Jan 2014 – 84hr Fcst: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d1_x_500vor+///3 |
This chart represents the height lines at the 500 millibar level of the atmosphere. Think of it as a topographical map, with the mountain to the south and the valley to the north. The flow in the upper atmosphere is geostrophic; that is, it is parallel to these lines of constant height. When these lines are close together, the geostrophic flow is faster. Look at how close the lines are together over our area, and think about what happens when fast moving air encounters a mountain range. It rises, right? And on the leeward side of this mountain range, it sinks. Now, take a look at the image below.
 |
| Valid 04:00 pm PST, Tue 14 Jan 2014 – 144hr Fcst: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_x_wa_pcp72+///3 |
The mountains get tons of precipitation, while the central Puget Sound area is completely shadowed because this flow is coming from the west-northwest, as opposed to our typical southwest flow, where Sequim gets shadowed. The northerly component is key because it helps keep our snow levels below pass level.
How many feet will Snoqualmie Pass get total from this storm cycle? I would guess at least four feet, which would certainly be enough for Summit West to open. We’ll see if I’m right!
Charlie
