Tuesday, November 22, 2011
This has got to be another quick post... I have class in 12 minutes, and I need to walk over there as well.
This isn't quite the "classic" setup for flooding in Western Washington. The reason? The snow levels are too low.
Many of our major flooding events have snow levels over 10,000 feet. Right now, it is absolutely dumping in the mountains, with snow levels around 6,000 feet in the south and 3,000 feet in the north. The Cascade passes, however, are seeing snow due to an easterly pass flow, keeping temperatures cooler there.
Eventually, this snow will shift to rain later today into Wednesday, and that presents a lot of problems for avalanches. The rain will put a lot of additional stress on the snow layers and act to lubricate it, making it more conductive for sliding.
This is for Tuesday and Tuesday night at Snoqualmie Pass, with the red denoting high avalanche danger and the black denoting extreme avalanche danger. The Northwest Weather and Avalanche Center had this to say:
"Tuesday and Tuesday Night: Avalanche danger becoming extreme above 5000 feet and high below. Natural avalanches are certain with large to very large avalanches in many areas. Avoid all avalanche terrain."
The passes will likely be closed for avalanche control.
One more thing... Seattle is not seeing heavy rain right now, as the band has shifted south. However, we will see heavy rain by noon as the band shifts northward again, and it will stick around until Wednesday morning. Overall, southwest Washington looks like it will receive the heaviest blow from this storm.