Larry Cosgrove = Pants Tent
“There is no fighting the notion that most of the lower 48 states are going to get swept up by the Arctic regime now descending from Canada. But there are questions about storm potential, especially regarding track and type of precipitation. Let me remind you that all of the numerical models show at least one massive disturbance passing out of the southern Rocky Mountains in the 6 - 10 day range. The ECMWF scheme is reluctant to allow the intense cold to reach the southern and eastern tier of the nation, which the GFS series is more aggressive and brings the forward edge of the cAk readings all the way into the Interstate 10 and 95 corridors. In effect, only California and Florida dodge the proverbial bullet.
It has been my experience that the American scheme handles cold advection much better than its European counterpart, particularly when a true Arctic air mass is involved. It is a judgment call, but the regime over North America is arguably the coldest in the Northern Hemisphere and will continue with that dubious title for the rest of the calendar winter. This is important because the path of storms in the medium range will likely be suppressed into the northern Gulf of Mexico and then up or off of the eastern Seaboard. I can see a scenario where the southern rim of the U.S. has a rain ending as an ice event, while snow deepens from the Great Plains into the Mid-Atlantic and New England states. Much of this is up for grabs, mind you, but the emergence of renewed blocking in Greenland, agreed upon by all of the computer models, will favor a lower latitude trajectory of impulses in the Arctic, polar, and subtropical jet streams. And the most obvious candidate is the broad cyclonic circulation below the Aleutian Islands
I note that most of the ensemble packages show yet another shortwave from the northern Pacific Basin getting caught up in the deviated jet stream configuration, with another deepening storm in the Southwest seven days from now. We have to watch this feature carefully! I can see a track scenario taking shape where the system drops into northern Mexico, then moves along the Gulf Coast,m and then close to and likely just to the right of the Eastern Seaboard. around February 14 - 17. This is the type of set-up that -could- produce a true monster winter weather event, with the Arctic motherlode being pushed into the Great Lakes region and phasing with the low pressure area. The vast expanse of cold is worrisome since actions like overrunning and cold instability will interact, with a wider coverage of precipitation types than is normal”