Monday, March 30, 2015

Snow at Snoqualmie Pass

Monday, March 30, 2015
4:28 pm

No, this isn't an early April Fools joke.

Snow actually is going to make a return to Snoqualmie Pass tomorrow.

Consider this: Snoqualmie Pass is "supposed" to have picked up 350 inches by now based on their five-year average, but to date they have only picked up 84. They've only picked up 10 inches since the beginning of February (six inches in February, four inches so far in March). In fact, March had been snow-less until the 24th, when Snoqualmie Pass picked up an inch.

But things are taking a turn for the snowier. An upper-level trough will settle over our area and direct cool, unstable air from the Gulf of Alaska into our region. Although the higher sun angles this time of year will still allow temperatures to heat up into the mid-50s, the air aloft will be considerably cooler, and this translates to steep lapse rates (decreases in temperature with height) and therefore relatively low snow levels. Take a look at the 72-hour snowfall valid 5:00 pm Thursday! Several inches over Snoqualmie, with much more at Stevens.

Valid 05:00 pm PDT, Thu 02 Apr 2015 - 84hr Fcst: Retrived from UW mm5rt modeling site

The reason there is so much more snow at Stevens is because a Puget Sound Convergence Zone is predicted to form and dump a lot of snow over there. However, if this zone moves south, it will drop this precipitation (almost certainly in the form of snow) over Snoqualmie Pass. If that happens, Snoqualmie Pass will see more snow in a day than they've received in 2.5 months! In the below 3-hour precipitation chart below, you can clearly see a convergence zone that has been pushed back into the Central Cascades.

Valid 11:00 pm PDT, Tue 31 Mar 2015 - 42hr Fcst: Retrieved from the UW mm5rt modeling site

Even more snow looks to fall in the days ahead, as more relatively cool disturbances from the northwest will slide on into our area. Going 84 hours ahead to hour 168 in our chart, you can see that there is still a significant amount of snow forecast throughout the Cascades with snow levels well below Snoqualmie Pass.

Valid 05:00 am PDT, Mon 06 Apr 2015 - 168hr Fcst: Retrieved from the UW mm5rt modeling site

If these forecasts hold, Snoqualmie Pass should see over a foot this coming week. Needless to say, operations won't be resuming until the autumnal equinox has come and passed, but it's still nice to be reminded that it does indeed snow there.

The record for minimum snowfall at the pass was set back in the winter of 1976-1977 when a measly 191 inches of snow fell. It's almost a given that we will break that at this point; we would need 107 more inches to tie it, and the most snowfall measured past April first for any year since records started being taken at Snoqualmie was 97 inches, all of which occurred in April. This occurred directly after a record-setting March total of 221 inches. Talk about some serious spring skiing!

Part of me is hoping that the snow that we do see will be minimal, because I'd like to keep the snow total for this year at or below 91 so that we can break the previous record by three digits. I'll settle for keeping this year's total under 100, though. Nevertheless, the snow will still be a very, very welcome sight for many, myself included, and I'll post some pictures in my next blog!

- Charlie

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