Weather Pattern Change by Early Next Week

The weather pattern across North America will be favorable for producing a period of cold weather across much of the central United States this week. However, this appears to be shorted lived as another major weather pattern change will take place this weekend. This looks to lead to a return to warmer conditions across much of the central and eastern United States by early next week.
The left hand side of figure 1 below depicts the current mid level (about 17,000 feet in the atmosphere) pressure fields in the atmosphere across much of the northern hemisphere.  The main features to note are the large area of high pressure across the Bering Sea and the Polar vortex of low pressure across northern Canada. The area of high pressure across the Bering Sea is called a “Blocking High”. This is because it acts as an atmospheric block, diverting the storm track northward across the high latitudes of Siberia and the Arctic Sea. Typically this drives the cold arctic air mass, emanating from Siberia, farther south and east across much of Canada and the northern United States (right side of figure 1).   This is depicted in the figure below by the large area of low pressure (blue colors) across much of northern Canada.  A pattern such as this typically produces colder and more active weather across the central portion of the United States.  Although this will be the case for much of this week, there are signs that this pattern will change by next week.

 

Figure 1: Current atmospheric pressure pattern across the Northern Hemisphere in the mid levels of the atmosphere (left), and current lower atmospheric air temperatures across the Northern Hemisphere (right). 

 

A strong upper level jet is developing across the mid latitudes of the northern Pacific (left hand side of figure 1 above). This jet is expected to undercut the blocking high across the Bering Sea. As this occurs, the blocking high will weaken and allow the polar vortex across northern Canada to be dynamically forced southwestward across Alaska and the northeast Pacific by early next week (left hand side of figure 2 below).  The main consequences of this altered pattern will be higher pressures aloft across much of the United States. These higher pressures will act to drive the cold arctic air mass back into northern Canada and Alaska next week (right hand side of Figure 2), bringing a return to a mild air mass across the region.  

Figure 2: Forecast atmospheric pressure pattern across the Northern Hemisphere in the mid levels of the atmosphere early next week (left), and forecast of lower atmospheric air temperatures across the Northern Hemisphere early next week (right). 

                                

So overall, if you like snow and cold it appears we will continue experience winter conditions across the area through Saturday. Thereafter, it appears temperatures will warm back above average next week. The figures below display the 8 to 14 day outlooks from the Climate Prediction Center. Notice that the Much of the continental United States has high probabilities of experiencing above average temperatures during this period. There are also enhanced chances for above average precipitation during the 8 to 14 day period. This would likely fall mainly as rain as we progress into a mild pattern.  

 



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