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    Waning Days of Summer Still Packing Plenty of Heat

    8/21/2013, 5:49:05 AM

    Wednesday, 10:30 a.m.

    We're about a month away from the autumnal equinox, and daylight is slipping away quickly. And let's face it. We've not had much heat at all so far in August, particularly east of the Mississippi! With the normals beginning to fall at a more steady pace, it will get harder and harder to reach 90 degrees in the coming weeks, plain and simple. But is summer over? Hardly. Just ask the folks in the middle of the country about that after yesterday:

    A number of records were toppled on Tuesday, such as the 87 in Laramie, Wyo.; the 91 in Duluth, Minn.; the 94 in Idaho Falls, Idaho; the 99 in Denver, Colo.; the 101 in Scottsbluff, Neb.; and the 102 in Bismarck, N.D. And the heat is hardly done there.

    The current setup has a large upper-level high anchored over the Rockies:

    Some heat is being squeezed into the Midwest ahead of a cold front that stretches from northeastern Minnesota into southeastern South Dakota and northwestern Nebraska. The air mass is considerably drier (much lower dew points!) on the northwest side of this front, and it won't be as toasty. Meanwhile, it could touch 90 in Chicago this afternoon, and temperatures will be within hailing distance of 90 in the Northeast this afternoon as well. It may make a run at 90 again tomorrow with enough sunshine and little precipitation. Then the heat and humidity will be taken off the playing field from the Midwest and Lakes to the mid-Atlantic for a few days.

    Meanwhile, back in the middle of the country, what trimming of the heat there will be is going to be short-lived. The upper-level high gradually rolls eastward across the Plains in the coming days, and by the end of the weekend, it's as far east of the middle Mississippi Valley. Look at the 0z August 21 GFS 500mb forecast for Sunday evening:

    Now look at the projected 850mb temperatures for the same time frame:

    That's +20C air blowing across the Plains into the Midwest! If it were the middle of summer, we would easily see temperatures jumping into the 90s. Well, it may be late August, but the ground in the Midwest is pretty dry right now, and the front coming through today won't bring them much rain. Therefore, there's every reason to believe it will surge into the 90s once again, and in the core of the heat, 100s could well be reached. Indeed, look at the 6-hour, 2-meter maximum temperature forecast for Sunday afternoon:

    And there's every reason to believe that 90-degree heat will reach Chicago and parts of the Ohio Valley on Monday and may take a stab at the mid-Atlantic on Tuesday! Even after that, there may be another surge or two of that heat out of the Plains and toward the East heading into Labor Day weekend and beyond. The problem with carrying the heat too far downstream is that there will be a northwest flow aloft that will cause the expanding heat zone to run into stiffer resistance. That's likely to lead to some showers and thunderstorms that would serve to cut the heat off at the pass!

    Regardless, the rumors of summer's demise have been greatly exaggerated. The waning days of it will still pack plenty of heat in large chunks of the nation.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com


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