In the previous post on 11/23/22 (read it by clicking here) the headline was "another swing and a miss?". I also discussed that this year's pattern was not quite set, or so it would appear. With the system this week (southeast of the area across mainly Oklahoma but a secondary moving well north) and the system moving by this Friday night and Saturday (again mainly southeast of the area), I believe I have a pretty good idea of the nature of the pattern. Is it concerning that much of the high plains has been left high and dry? Absolutely. But with the changing of the seasons (fall into winter, winter into spring, and spring into summer), the pattern will shift around enough that it won't be totally gloom and doom. Now to time it.
The system(s) the past 2 days brought good moisture to Oklahoma again (and into the Corn Belt). Here is a map of that precipitation.
During the past 2 weeks there was "some" precipitation farther into the plains, but not a lot.
The biggest weather news this next week will be a monster storm that is going to impact much of the central part of the country with a blizzard across Nebraska and the Dakotas and severe convective weather farther south and east. There will be a big concern for a possible outbreak of tornadoes across the Mississippi Valley. For the high plains (at least the central and southern high plains), it looks like more of the same with dry and way too much wind. But....
In the past few meetings and presentations that I have been doing, I mentioned the second half of December could be active and very cold. I've expected this for several weeks because of some connections to the tropics with the higher latitudes; possible blocking of the jetstream;, and a buildup of snowcover across the northern hemisphere. One thing I look at in a shorter time frame (less than 30 days) is the indices of the Arctic Oscillation and the North Atlantic Oscillation.
It's not unusual for these indices to go strongly negative. When the Arctic Oscillation goes strongly negative, it is often followed by a deep intrusion of Arctic air into lower latitudes. Sometimes it's across Europe or Eurasia and sometimes into North America. It just depends. When the North Atlantic Oscillation goes deeply negative, there is usually blocking of the jetstream across the Atlantic and into Greenland. When this happens weather systems tend to slow down and move more meridional. But, when both the AO and NAO go negative, there is quite often a major intrusion of Arctic air into North America, including the U.S.. That is one clue that December is about to get frigid. Then top it off with the snow that has built up across the northern hemisphere...
BTW, that area of snow cover across the northern hemisphere had been above record levels and still is above the 56 year mean. Interesting.
With all this going on and with the pattern that is setting up, the jet stream flow is going to become (or has become) very energetic and volatile. After this major storm moves by early next week, the remainder of December will, on average, be colder than normal with periodic episodes of snow (including snowfall for the high plains). The way I see it, many locations across the central and northern U.S., will have a white Christmas or at least the odds favor such.
As far as precipitation, here is what the Weather Prediction Center is expecting through the end of next week.
With me wrapping up my career in Meteorology with the NWS, I'm not having much time to update this blog but I will attempt to do so again next week. As mentioned, a month ago or so, changes will be coming to this blog. More later.
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