Evaluating the Lower- and Upper-level Flow over North America (credit: Thermodynamic Solutions)

DISCUSSION: As the present national weather pattern stands, there is quite an interesting set-up in place across the United States.  One of the first thing atmospheric scientists (i.e., operational forecasters and/or broadcast meteorologists) execute when doing a given forecast is to ascertain a more concrete foundation of what is currently happening at that given time near both the top, middle, and bottom portions of the "active" atmosphere.  The "active" part of the atmosphere referring to the portions of the atmosphere within which a large majority of the global weather phenomena occur within the confines of.  As you can clearly see in the graphic above (courtesy of the Thermodynamic Solutions Weather Company), there are very different atmospheric flow regimes in place closer to the surface and towards the middle-to-upper portions of the atmosphere. 

This is chiefly due to the fact that in the middle-to-upper part of the atmosphere, there is presently a "ridge" (or an area of high-pressure) in place over and across a good portion of Western North America which is shown on the right-hand side of the graphic attached above.  To the east of any ridge can often be found a "trough" (or an upper-level region of lower pressure) which is also reflected by the "dip" or "deep left-turning curve" in the deep-blue colored flow shown on the right-hand side of graphic above as well.  On the right side of any trough is where you nearly always find a higher probability of there being a greater likelihood of low-pressure formation.  This is a combined result of there being stronger cyclonically-turning winds from the surface upwards on the eastern side of a trough which is much more favorable for surface-layer cyclogenesis which can then extend into the mid-levels of the atmosphere as well under the right conditions.  Sure enough, very far downstream, there is a strong low-pressure system parked over part of Southeastern Canada which is helping to amplify a good portion of the ongoing lake-effect snow events downwind of Lake Erie, Lake Ontario, Lake Michigan, and Lake Superior.  Thus, it is always neat to see how atmospheric science theory works out in real-life application.

To learn more about other interesting weather events occurring across North America, be sure to click here!

©2017 Meteorologist Jordan Rabinowitz