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Spate of Severe Storms Giving Way to Summer Sizzle

5/26/2011, 6:50:43 AM

The Memorial Day weekend is just about upon us, a time when most really start thinking 'summer.' Up to now, the spring season has been, in a word, violent. The latest run of severe weather has been every bit as wild, destructive and deadly as what has come before. The good news is that it will back off considerably in the next 24 hours, and there will be much less of it through the holiday weekend. As the severe weather eases, it's going to look and feel a lot like summer in much of the country all of a sudden.

First, the severe weather. Here are the severe weather reports from the past three days, starting with Monday and Monday night:

Then, Tuesday and Tuesday night:

And finally, the past 24 hours, the most active of the three days:

The worst is behind us, though we're not out of the woods just yet. Take a look at the 500 mb chart from this morning:

That upper-level low rolling across the Mississippi Valley into the Ohio Valley represents a pocket of very chilly air aloft. Meanwhile, at the surface, it's warm, and it's pretty humid, too. And where there's any kind of sunshine in and west of the Appalachians, it will take almost nothing for the atmosphere to destabilize to the point at which strong thunderstorms will develop. Some of these will be accompanied by large hail and damaging winds, and the risk of tornadoes is still relatively high.

By the end of the day tomorrow, though, that upper-level low will look a lot less impressive:

While weaker, there's still some residual chilly air aloft, enough so that with some daytime heating in parts of the Northeast tomorrow ahead of the feature, strong thunderstorms can again flare up.

There's also a worry that the system plowing through the Northwest and across the northern Rockies may spark some gusty thunderstorms over the eastern Dakotas into Minnesota late tomorrow and early tomorrow night. As the warm, increasingly humid air quickly tries to return to the southern Plains from the Gulf of Mexico, there may be a flash point over portions of Oklahoma and Kansas into Arkansas late tomorrow night for some potent thunderstorm to erupt:

Heading into the weekend proper, though, the Eastern feature will further weaken. The one coming across the northern Plains will bypass the northern Great Lakes. There will be a boundary separating growing heat and humidity across the southern tier of states from the lingering chill across the Northwest, the northern Rockies, and the northern Plains. Along that boundary, there can be some showers and thunderstorms Saturday and Saturday night into Sunday, but that boundary will be in retreat to the north on Sunday in the face of a burgeoning upper-level ridge over the lower and middle Mississippi Valley into the Ohio and Tennessee valleys, not to mention the mid-Atlantic states:

The GFS expands this ridge on Memorial Day:

This ridge will hold its ground over the East through Tuesday before that disturbance crossing the northern Plains rolls over the top of the ridge and finally pulls a cold front through the Northeast and mid-Atlantic later Wednesday and Wednesday night, ending the run of heat in those areas. During that time, though, there may be quite a number of places that reach 90 at least once, if not two or even three times! And with it, fairly high humidity, too. Perfect timing to open up the pools and for the beaches and lakes to be packed over the holiday weekend!

Later in the week, as the Northeast cools down, the upper-level ridge will merely shift westward, and the focus of the heat will shift back into the Plains and eastern Rockies. In some cases, the change from Saturday and even Sunday to next Thursday and Friday will be nothing short of astounding--potentially more than 40 degrees with high temperatures in that span!

Unfortunately, the one place that will not see much sign of summer in the coming week will the West--temperatures should remain cooler than average from Washington to much of California for the foreseeable future.

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

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