Here Comes The Roller Coaster

10/19 Tuesday 9 am

Last night’s light precipitation event has come to an end in most areas. Isolated showers may linger a while in the Northern San Juans and over Wolf Creek.

AR events, also known as an Atmospheric River have become an overused term that the weather media has become obsessed with over the last few years. It is right up there with the dreaded Polar Vortex. Both are coming but one will be sooner than the other.

For those of you old enough to have gray hair, we used to know Atmospheric Rivers by the name of The Pineapple Express. This is not to be confused with the bad movie of the same name.

Over the last few days, I talked about the MJO going into phase 1 after the 24th. I also said I would talk more about the MJO, which I will, but not right now. The result of the MJO in phase 1 translates to cooler, wetter conditions for us.

The models are still struggling with exactly where the MJO is going to end up. The GFS has transitioned towards phase 1 over the last couple of days, now this morning it is backing off slightly. There is only one model showing the MJO going deep into phase 1.

The Euro has backed off from where it was a couple of days ago but seems to at least make it there. The Canadian model is similar to the Euro, stalling around phase 1.

The Japanese model is showing a deep trek into phase one. The deeper the model goes into a particular phase the higher the confidence in the resultant conditions for the phase. The Japanese model is a highly regarded model, especially for long-term seasonal modeling and for ENSO (El Nino/La Nina).

My problem with AR events is the majority of the time they do not live up to the hype. They run out of most of the precipitation before they get here.

Here is the Euro in motion.

This is the regional view, I am going to stop it right as it reaches Colorado.

Check out the precipitation accumulation for California.

That is 6 to 12 inches of liquid across the Sierra.

How about snow?

It is difficult to see but that is 40 to 80 inches of wet snow in the higher elevations.

OK, back to our area.

I am going to use static images otherwise it goes too fast.

Tuesday morning the moisture arrives.

Tuesday at noon!

Tuesday 6 pm…

12 am Wednesday morning.

Wednesday morning 6 am.

Euro precipitation total

Euro snow


That was a very extreme example of what I don’t like about AR events.  I do not think it would be possible for that strong of an event to end up like that for Western Colorado. However, that is what it sometimes feels like around here. Here is a look at the other models. I will spare you the run-up and drama and just cut to the totals.



I think the Canadian is the most believable of the three.

I know I mentioned the Polar Vortex earlier. That won’t be for a while, and it is way too early to figure out where it is going to end up over North America. Historically, if it is going to affect our region, it drops into the Upper Great Lakes or Upper Midwest then retrogrades west spilling colder air into our area.


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One thought on “Here Comes The Roller Coaster

  1. Ruth Ann Thompson

    Good morning Jeff,

    We got .08″ of rain last night – I was really happy about that. We live off Hwy. 184 on Road 38.7, about 5 miles northeast of Mancos.

    Ruth Ann

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