October may wrap up with more persistent cold in a sizable part of the United States from a significant change in the jet stream pattern beginning later this week.
Over the past couple of weeks, we've seen some significant cold fronts sweep through the Plains and East, bringing an end to a record early-October heat wave, ushering in some first frosts and freezes of the season while spawning an intense Northern Plains blizzard and Northeast bomb cyclone.
In the wake of these systems, the cold air in the Midwest, South and East has generally been short-lived, lasting one or two days before a warmup ensued.
By later this week, however, a change in the pattern should allow cold air to not only plunge deep into the U.S., but also lock in place for a while.
Computer forecast models suggest two northward bulges of the jet stream are expected to form. One of these near Greenland is what meteorologists call a "Greenland block." The other may bulge north just off the West Coast.
Between these two northward bulges, the jet stream has to plunge south. When it does, the cold air trap door is wide open into the U.S.
But it's the persistence of those blocking northward jet stream bulges that typically allows colder air to last longer than a few days.
That's precisely what the forecast models are suggesting. This cold air, once in place later in the week, could last through Halloween, or perhaps the first weekend of November, over a large part of the nation.
One uncertainty in this colder outlook is how much seeps to the East Coast and how persistent it will be there. Depending on the exact orientation of the jet stream, the cold air could plunge more south through the Plains than east.
The highest confidence of persistent cold to end October is in the nation's midsection.
Parts of the Southeast – Florida and southeastern Georgia, in particular – may be among the few spots to escape this persistent cold near month's end.
The first half of October was among the five coldest on record in much of the Northwest, northern Rockies and parts of the Northern Plains, according to the Southeast Regional Climate Center.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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