Joe Lundberg

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Welcoming in Summer with a Blast of Heat

June 18, 2012; 10:13 AM

Monday, 11:35 a.m.

While residents of the Northeast and mid-Atlantic have enjoyed a run of normal to somewhat below-normal temperatures, especially this weekend, record heat has been in play elsewhere around the country. Denver, for instance, set a new record for June 17 when they hit 98 in the afternoon, and considering it's already 87 there at 9 a.m. local time and 6 degrees ahead of the pace set yesterday with blazing sunshine, chances are good today's record of 99 will get wiped out.

The heat in Denver is probably being made worse by the fact that everything is so dry there. There's so little moisture to evaporate that most of the sun's energy is going into heating the parched ground and, in turn, the air near the ground. Even though Chicago did manage to get some rain Saturday night and early Sunday morning, most of that moisture will be evaporated today and tomorrow with blazing sunshine and very strong south to southwest winds. In other words, they will have little trouble soaring into the mid-90s.

This expanding heat is a product of several things. I've already mentioned the lack of rain in some areas. Look now at the current jet stream:

The center of the upper-level ridge is parked over northwestern Mexico, but the main jet stream flow is well to the north, through Oregon into Wyoming. The temperature contrast from one side of the jet to the other is nothing short of extreme. And the upper-level disturbance flying through the Northwest into the northern Rockies is driving a cold front along. Winds tend to get stronger in the vicinity of cold fronts, both ahead of and behind them. Given the full complement of sunshine along with the bone-dry air mass, it's pretty easy to send temperatures into record territory.

Strong thunderstorms will also erupt but only around the rim of the heat. That feature zipping through the Northwest and northern Rockies this afternoon and tonight will draw upon the hot, humid air mass surging toward the northern Plains and Midwest, triggering some violent storms tomorrow afternoon from portions of Nebraska and the easternmost Dakotas into Minnesota.

After a three-day run heat in the Midwest and western Ohio Valley, a cold front will race along in the flow. The most active time period in terms of severe weather potential could well be tomorrow afternoon and tonight, though I think Wednesday will also be pretty active as well across Iowa and Wisconsin into northern Michigan as well as northwestern Illinois. After that, though, the front will weaken enough so that the shower and thunderstorm activity tied the front is less likely to be severe. It is quite conceivable that portions of the Northeast and mid-Atlantic get precious little rain from the front when it passes Thursday night or Friday.

That leaves the East to experience the heat, and they will not be denied. Once the marine influence is turned aside tomorrow, it's just a question of how high it'll get Wednesday and Thursday. The hottest day will clearly be Thursday east of the mountains. Then we'll see an abundance of sunshine combine with the very same toasty air mass and a west or west-southwest wind downsloping off the mountains. While few places will top the century mark, many will be well into the 90s. Combine that with dew points well into the 60s, and it will drive AccuWeather Real Feel temperatures well above 100. The saving grace is that it should be well ventilated. In other words, it will be pretty breezy to downright windy at times. And by Friday, the heat will begin to back down before being erased over the weekend.

The official start of summer is Wednesday evening at 7:09 p.m. EST. After that, the days will start getting shorter and shorter. Now that's a cheery thought, isn't it? Ummm, no. I've been waiting a long time for summer to get here, and I will not be in any hurry to see the days grow shorter, though there's not one thing any of us can do to change it!

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

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About This Blog

Joe Lundberg
Joe Lundberg, a veteran AccuWeather.com forecaster and meteorologist, covers both short and long-term U.S. weather on this blog.