So today is day 10 since we started seeing the pattern change coming for next week. We started counting down the 14 days until the ridge off the coast moves 10 days ago with day 14 being Tuesday. Although the forecast models are all over the place with what will happen with the storms when the pattern changes, the overall trend with regards to the setup of the ridge and the blocking is very similar and consistent.
Just to recap, we are watching for the ridge to shift North starting Tuesday, then reform South of the Aleutians towards the end of next week, then push up into Alaska next weekend, and maybe spread Southeast into Western Canada beyond. This would setup blocking sending storms underneath into the West Coast. It’s way too early to know what will happen with the storms if this pattern develops but we know what can happen. The forecast models have been all over the place but several runs a day do show the storms breaking through. Let’s run through latest 18z GFS which goes right in line with my thinking.
We’ll start with the pattern for Saturday. The ridge of high pressure is the circle off the West Coast where the number get higher as you go towards the center. This is where it has been for the past month blocking storms.
Here is next Tuesday the 10th as the ridge shifts North and West.
Then the ridge shifts inland as a new one develops South of Alaska and the Aleutian Islands. The door is now open for not only storms but for cold to drop down from the North.
Then the ridge continues to build into Alaska by Sunday the 15th as the cold pushes South through CA. In this frame light snow has already pushed through with the cold front and storms are approaching from the North and the West.
Then by Tuesday the 17th the ridge over Alaska spreads Southeast into Western Canada blocking all storms underneath. At this point the tracks are laid for the storm train.
This is where it gets good so let’s zoom in for Friday the 20th.
And Sunday the 22nd….
This is where the GFS ends but you can see where this pattern can lead. With the low sunspot count and the stratospheric warming the AO continues to trend towards negative and that usually mean blocking is on the way. Keep your fingers crossed that we get a pattern like this one. Right now is looks like the storms could start as early as next weekend or later into week 2.
Here is a blend of the models for the week 1 precip on top and week 2 underneath. So you can see the model consensus right now is for snow week 2 after we go through the pattern change week 1.
Now I may be one of the few forecasters dumb enough to show these charts for storms more than a week away, but I have been scrutinizing everything about the long-range and when snow will finally get in here. I would not start putting this stuff out if I didn’t feel like confidence is growing. You’ll know to get excited for real when I start to forecast actual snowfall amounts. Stay tuned….BA
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