The interaction between the Gulf of Alaska vortex and the subtropical jet stream returns the threat for major cold and stormy weather to North America by March March 7. I realize that many of you are probably sick and tired of reading about that gyre setting up below the Farthest North State. But as a function of a La Nina episode, the sprawling vortex is often recurrent and one of the dominant factors in altering sensible and apparent weather in Canada and the U.S. during the winter months. Forecast rules for the GOAV are easy to remember. If the cold 500MB circulation is stable or stationary, then the lower 48 states and southern Canada will come under a mild, largely inactive, semizonal flow. But should the monster vortex be progressive, and shift to points like the Lake Of The Woods or James Bay, there will be breakout surges of Arctic air that sometimes reach down to Mexico. The saving grace for parts of Dixie and the Eastern Seaboard is that there will often be a Southeast (heat) ridge be present, which keeps the cAk regime from getting to the Interstate 10 corridor. This is exactly the pattern I describe for the first week and a half of March. The chill seen now in much of the continent may alleviate in the 6-10 day range (though I doubt that the Midwest, Great Lakes, and Northeast catch much of a break from the freezing weather). But that big storm in the northeastern Pacific Ocean will be on the move, with snow and cold over the Intermountain Region. Forming what I think will be a Colorado/Trinidad "B" path scenario (eastward to Virginia and then off of the New England coast). the floodgates to bitter cold and a late season snow event will push through the Great Plains and Midwest into the Northeast before the middle of March. Then, with any luck, the subtropical high in Florida will expand, and slowly force out the tundra air mass. Have a nice weekend, everyone!
How about this toppop and he has been spot on all winter