BALTIMORE - Mike Masco
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Since late November, I have been pushing the idea that a pattern change would occur, plummeting the east coast into cold and snow by December 14th/15th. We sit here on a Sunday evening scratching our heads and saying .. Well, where is our pattern change?
As I have said all along you could have the best set up on the eastern sea board (negative NAO, strong Arctic Oscillation) yet, as long as the Pacific does not play nice much of that will be wasted.
What is going on in the Pacific now has lead to a very cool western USA while the eastern US states remained warm. Storm after storm has forced a dip in the jet stream known as a "Trough" over the west coast. When you dip the jet stream out west, you force an over abundance of mild pacific air over much of the United States. This has blocked all the arctic air from coming south and east leaving us with above normal temperatures.
I firmly believe that once we open the cold source region up (in red) and transport it south we will not break the cold pattern. There is just too much cold air available and even if it was modified a bit it would still be COLD!
Where do we go from here?
The fact is the NAO has been negative (which we usually say is a good thing) however, it has been on the wrong side of the Ocean. For the last three weeks we have seen a block stretching from eastern Greenland into northern Russia favoring cold over Europe. Well, that is about to change.
The block will shift more west going into what we call a WESTERN BASED NAO. The GFS and European models say this block will extend right into western Canada linking up with another ridge over the Gulf of Alaska. This will shove the cold air south pushing the main jet stream to the southern states (opposed to the northern states where it has been). Two things can happen from this. 1. we get very cold and stay cold with NO storms (storm track is supressed) or 2. We get cold with the potential for a very active situation. It will depend solely on the mean position of the jet stream over the western US and how much ridging we see (dips over the central USA).
GFS: Showing height anomlies. Red means HIGH PRESSURE Green= Very low pressure
The European is also on to this idea. You now have strong heights building over western Greenland (STRONG NAO) sending the storm track further south. Key ridging over the USA will determine if a storm gets stuck south of the Mid Atlantic, sending it up the coastline (snow storm track). This is a classic snowstorm look over the east IF THIS SOLUTION PANS OUT!
IMAGE DECEMBER 21 ST
While I can admit I am off on the timing of this change I do feel right after this weeks series of storms we will grow much colder. While I have a few 50's in my 7-DAY forecast which accounts for the storm track of Tuesday and Thursday storms running NW of Maryland I do believe we are easily into the 40's to close out this week (that maybe too high) !