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Another Dramatic Weather Week Is Ahead Of Us

Good morning bloggers,

We begin the day with a very complex weather pattern producing a unique set up across the Northern Hemisphere. There is a split in the jet stream north of Hawaii and south of the Aleutian Islands. The northern stream then bends around an upper level high over southern Alaska, and the southern stream dives south to near Hawaii and then across the southwestern United States:

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There is a wave in the northern branch that is an important factor today.  And, the big upper high and ridge over the Gulf of Alaska is creating the conditions for a continued maintenance of the Arctic air mass, with the true Arctic Air mass being held to the north in response to an AO+ (Arctic Oscillation).  Even though the coldest air is far to the north, a United States born very cold air mass has formed in the wake of the weekend snowstorm and blizzard, and it has dropped into areas just north of Kansas City this morning.  The interaction of the northern and southern branches of the jet streams is creating some weather forecast problems. That strong wave in the northern branch is just the first in a series of such waves. Each time one of these tracks just north of the United States, a cold surge will push south, and then it will relax, and warmer air will try to force its way back in. On Wednesday, the next wave will track across southern Canada with another cold surge. And, then the southern branch is likely going to produce a weak disturbance that will increase the chance of light precipitation.

Today at 4 PM:

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Forecasting just today’s high temperature is quite difficult, as you can see above. A front is going to be nearly stationary and lifting very slowly north. A stationary front is defined to move slower than around 10 mph, and this front will just be drifting around.  On Tuesday, it is still forecast to be nearly stationary.

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Then by Tuesday night, there will be a weak wave in the southern branch of the jet stream racing across and there is likely going to be a little band of precipitation with light freezing rain possible. This needs to be watched closely as temperatures will likely be in the 20s north of that front.

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The front will then become a cold front and push south on Wednesday.  We will then look ahead to later in the week. We are moving into cycle 4 of this years LRC and it begins with the part of the pattern that has produced wet storm systems in the first three cycles from 10″ of rain, to the blizzard in late November, to the snowstorm on January 12th. This time, however, there is a stronger influence from an AO+. Take a look at the latest index:

Screen Shot 2019-02-25 at 6.07.27 AM

I am convinced that Kansas City would have had a much better chance of being even closer to the weekend snowstorm if the Arctic Oscillation were not so positive right now, and this is likely having an influence on the beginning of cycle 4:

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This wave is directly related to the first three cycles, and right on schedule.  In the other three cycles, four days out, the tracks were all predicted to be north and weak, and then they strengthened and produced. The models were absolutely wrong in each previous cycle at this point. The difference this time may very well be the higher AO+.  A bit farther south and it will snow significantly on Friday evening:

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Slightly farther north, then you can lift that Friday evening snow into Omaha and Des Moines, leaving KC with flurries and a cold blast.  And, slightly farther south or southwest on that wave, and a few inches of snow would be likely.  Either way, the storm is right on schedule. Let’s see how the models trend today.

Thank you for spending a few minutes of your day reading the Action Weather Blog featuring Weather2020 and the LRC.  Have a great start to the week.

Gary

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