WEATHERAmerica Newsletter; Wednesday, February 5, 2025

[Larry Cosgrove]

A Challenging Weather Pattern And A Looming Threat For President's Day Weekend

There are many elements to the atmospheric set-up that will make life miserable for some, but enjoyable for others. The good stuff will be in Florida, where temperatures are likely to stay well above normal at a time when most of North America will be crying out for Spring. It boils down to position and action by three key features at 500MB: a massive blocking ridge that starts in Alaska, then grows to encompass the entire Arctic Sea and Greenland; a persistent cAk vortex formation that starts in British Columbia, matures in Ontario, and progresses into far eastern Quebec; and a very early version of the Bermuda High, which for now can be termed a Greater Antilles/Sargasso Sea positive height anomaly.

It works like this: the subtropical high wants to pump up warm and humid air into the eastern half of the nation. The vortex, with a recurrent extension or trough across the western U.S., tries to dump Arctic air in the same general direction. Surface cyclogenesis results about every four days, and these impulses are meant to neutralize the difference in temperature. As for the sprawling block that eventually comes to rest just below the North Pole, that high latitude ridge complex keeps the brutal cold from easily moving and minoring out. But the interactions never occur easily, which will mean some stormy conditions in the lower 48 states for the next two to three weeks.

I suspect that the next two disturbances in the series will be of moderate strength. A cold dome aloft, working with some moisture, could produce very heavy snowfall from Ontario and Quebec through the interior Northeast. Freezing rain and sleet could be a concern in Appalachia before the cold and dry part of this regime takes over. Another shortwave moving out of the Pacific Northwest looks to bring light/moderate snow to the Great Lakes Region, St. Lawrence Valley and New England. But warmth and moisture drawn into this storm will modify the earlier cold intrusion. Temperatures in much of Canada and the northern tier of the USA will be quite cold.

And this is the difficult part, as most data suggest two more storms impacting much of the nation, from the West Coast to the Eastern Seaboard. While the cold returns February 12 or so (advancing to the Gulf Coast and Atlantic shoreline), two stronger mid-latitude cyclones will be in polay. Unlike the preceding systems, these will likely take a more southern track. Severe thunderstorms and heavy rain may target Dixie, while a heavier brand of snow and ice progresses from the Intermountain Region through the Mississippi Valley into the Virginias. There is real potential for travel and power issues from February 13 - 18 from the Midwest into the Northeast, followed by another punch of Arctic air.

Stay tuned....