Good morning Weather2020 bloggers,
We are now moving through the big Thanksgiving week with a big storm developing. All weather forecasts are complex because we are predicting the future. But, some are even more complex than others, and this week has many of those challenges. Let’s take a look:
Energy is now coming into the Pacific northwest coast as a trough, i the shape of a tilted V. We have seen energy come into the flow in this configuration as this pattern began setting up in September and October. The flow is unblocked and the AO and NAO indexes are well above zero. A strong cold front is developing anyway and it is about to surge southeast into the plains states. What happens with this energy in the flow is rather fascinating during the next few days.
The upper low forms and closes off by tomorrow evening, as you can see on the right. The flow is still unblocked over Canada. There is a northern branch wave developing, and this wave will likely push the cold front through Kansas City earlier than previously forecast by the models, but it is still just Monday, so let’s keep monitoring it.
The evolution of this pattern in the next seven days may end up bringing Kansas City it’s first chance of snow.
This next map, on the left, shows one forecast solution for Thanksgiving night. A high over low is trying to form near the west coast. The models historically have a very difficult time forecasting these blocks and then they have a very hard time forecasting what will happen next. This pattern is actually quite similar to how it set up in early October, but with so much more energy now into the flow we are about to experience something rather fascinating this week. Now, how will it impact us, and what comes out of this pattern early next week?
Look at what happens by Saturday night. The upper low reforms/evolves and is forecast to be spinning over the west. The high over low blocking only is forecast to last a very brief time with the main flow continuing at very north latitudes over Canada. Forecasting what will happen next is going to be quite difficult. The surface will be in “chaos” after the front pushes south, and how it sets up later this weekend will decide who has a chance of winter precipitation. We will look at the surface map for Thursday evening, and for next Monday, but first look at one solution for how the upper low comes out early next week.
Look closely at this fifth map that I am posting this morning. There is a well defined northern branch over Canada. This flow is a symptom of the AO and NAO staying positive. There is also a southern branch, stronger than normal, and likely a somewhat direct influence from the strong El Niño. The upper level low circulation is forecast to track north of KC, and this would usually indicate that any chance of snow will track to the north. Where will the system really track, and due to the surface being all “messed” up there are all kinds of potential solutions for us to analyze. Okay, here are the two surface maps:
The trend on the models has been for a bit more northern branch dipping into the Great Lakes by Thursday. This would likely help push the cold front farther south. It’s still just Monday, so let’s see how this trends in the next few days, but this solution would be cold and wet for the traditional Plaza Lighting Ceremony Thanksgiving Night.
This second surface map shows one of many solutions for early next week. The blue dotted line, the first one that extends from northern Oklahoma to northeastern Missouri would be the likely rain/snow changeover line. Let’s hang on and try not to analyze this too much. There is a lot that will be going on between now and the end of the holiday weekend.
Have a great start to this holiday week. Thank you for participating in the LRC Forecast Experience blog!