“Winter-like” Pattern Setting Up Across The U.S.

Before someone takes the title of this article to mean that winter temperatures are on the way in the middle of summer, that is not at all what I’m saying. The overall pattern that is going to start setting up across the U.S. this upcoming weekend is going to be very reminiscent of the pattern that has been quite common over the last two winters with a trough in the eastern U.S. and a ridge farther west. Even throughout last summer, the jet stream dipped unusually far to the south, keeping the pattern anomalously cool for much of the central and eastern U.S.

So far, this summer (meaning the meteorological summer) has been very different than what many of us have experienced over the last couple of years. Ridging has dominated much of the Southern U.S., bringing a heat wave to both the Southwest and Southeast. A weakness in the ridge has kept the Southern Plains cooler, which allowed Bill to work its way northward into the area and around the Southeast ridge. As the month has progressed, parts of the Northern Plains into the Northeast have cooled off quite a bit, but overall, the pattern has been stubbornly persistent.

The stubborn ridge across the Southeast is going to begin breaking down this weekend as a broad trough moves in and builds well south, bringing much cooler and less humid temperatures across much of the central and eastern U.S. with Florida being the only location in the eastern U.S. that hangs on to the above average temperatures. The change will be very noticeable. At the same time, a ridge is going to build over the western U.S. well into the northwestern U.S. and northwestern Canada. While the focus of the warmth in the West has been over the Southwest, that focus is going to shift over the Pacific Northwest, where temperatures will likely challenge or even break records. As you can already tell, this is the pattern of extremes that we have all become acquainted with by now. Many locations will get a shot at rainfall/storms by this weekend in the eastern U.S.

The Probability Of Above Or Below Average Temperatures From June 29th To July 3rd:

Probability of cooler temperatures

I wouldn’t be surprised if this pattern sticks around for awhile, especially keeping the Great Lakes and the Northeast cooler with the western U.S. staying warm into July. The biggest uncertainty that I have right now is whether or not the ridge will try to build back into the Southeastern U.S. as we head a little farther into July. Sometimes it’s hard to break out of a hotter pattern in the Southeast during the summer once it has already become established. The forecast models try to build Bermuda high pressure back farther west into the Southeast, which would mean more heat, however, if this ridge stays suppressed, the Tennessee Valley into the Mid-Atlantic and northward could stay cooler, while the Gulf coast states would get hot again. In between all of this, there could be a zone of very wet and stormy conditions, which would probably be into the Tennessee Valley and/or Ohio Valley and north/east. Anyway, I’ll get all of those details ironed out as we get a tad closer to July. In the meantime, enjoy the cooler temps in the central and eastern U.S. that will be arriving by this weekend or sooner for some of you.

Notice The Broad Trough Building In The Eastern U.S. With A Ridge Building Over The West:

Trough In Eastern U.S.

  • Jon Davis

    Don’t worry, most of us realize that in the summer, when you mean winter like pattern, we’re taking it that you mean the weather’s behavior, not that the temps are suddenly plunging like we’re in the second half of Day After Tomorrow. (Fun movie, crappy if it happened for real…((not to mention scientifically inaccurate as all get out…))

    • matthewhlldy

      I always mention it because I always have that one person who says I’m forecasting a blizzard in July. 🙂

      • Jon Davis

        LOL, hope springs eternal in the heat of summer.

  • Jessie Carman

    And let’s be clear: in those charts the intense blue doesn’t mean “very much below normal” (large delta-T) it means “very large probability”. The documentation tells you this, but few people read that. The delta-T may in fact be moderate or small.

    • matthewhlldy

      Unless someone failed to read the sub-heading, that should be pretty obvious. Unfortunately, there are a few people that only look at the maps and nothing else.