Just saw the weekly 500mb height maps from last night’s monthly run of the ECMWF. Ridging wants to hang around the West Coast much of the 2nd half of December. Here is the first week showing the troughs impacting us at times. They are weak and splitty, evidenced by the highest anomaly to our south. This is bad for skiing, no significant snow (2 feet or more) on the way:
Then Christmas Week a change back to the November pattern we saw with ridging hanging right over us or trying to shift back a little to the west. We turn very dry, although the ECMWF today has warm rain in the Cascades as the ridging is getting established Sunday through Tuesday next week:
It’s interesting to note the ensemble average seemed to be farther west yesterday, putting us on the edge of “backdoor” arctic air invasion. Even the 12z ensemble average that just came out midday looks like that. Slightly under two weeks from now:
Back to the monthly run…Week 3:
A bit more north with the ridging, this could let some systems through underneath it…into mainly California. We saw this in November a bit. Mild West Coast and cold eastern USA.
And the final week which takes us almost to mid January…looks a classic “El Nino” setup again with a strong jet into California and the ridge has moved farther north. This could be wet at times over us, similar to what we’ve seen early in December.
Remember this is just one run, although it is many different ensembles averaged together too. The main message I take away from this is the ECMWF shows no cool/snowy westerly-flow pattern for the Cascades in at least the next 2-3 weeks. That was totally absent last winter as well. At least until the floodgates opened the 2nd half of February!
I’ll probably blog more on the pitiful (and possibly record-setting) state of the snowpack in the Cascades late today.
Chief Meteorologist Mark Nelsen