It gets tempting when tracking a storm to just skip forward and check out the totals and post them. It probably seems like that is all I do. In a changing weather pattern like we are entering you really have to take a look at the whole picture because the models are struggling from a seasonal perspective and because of the whole long wave pattern. They each have a different idea of which features are going to be dominant and when.
Troughs typically go from west to east but depending on a few things, systems can get clogged up as they try to make their way across the country. Sometimes we see the trough position change due to a cold front dropping in the middle of the country then retrograding the cold back to the west. How the models interact the low pressure to the west with the cold front to the east leads to a variety of solutions and model uncertainty. Time is the only thing that helps the models resolve their conflicts.
It is easier to show you than to explain.
Here is the Euro map on Thursday morning. You can see the position of the low pressure (the blue circle above Las Vegas). The cold front I mentioned cuts through the upper midwest from southeast to northwest, you can see the blue lines with 540, 534 and 528.
Compare those two positions with the GFS’ depiction at the same time on Thursday (below). Much colder air is in the midwest. See the 522 and 516 blue lines? That is very cold air. The low pressure is not in Vegas like on the Euro, it is actually the red circle that says 546 over the Four Corners Region, it has moderately heavy snow falling across SW Colorado.
The Canadian has the coldest air and it is further southwest with the cold front than the other two models. Notice how that 540 line drapes across NE Colorado? That is several hundred miles southwest of where the Euro has it. Also, the low pressure (the red 546 circle) takes up most of the state of Arizona.
Three different models, three different ideas and about four days to figure it out. I equally distrust the three models at this point. I am anxious to see what they come up with tomorrow.
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