Joe Lundberg

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The Highs Have It

September 24, 2013; 11:18 AM ET

Tuesday, 11:55 a.m.

High pressure is the most notable weather feature on the weather maps today! Oh, I know. That's not a newsworthy headline by any stretch of the imagination! Who wants to watch the national news if it is filled with stories of good news and wonderful deeds? Face it! As a society, we crane our necks when we see accidents on the opposite side of the highway just to see the damage inflicted on the cars. Many tune into an auto race for the spectacular multi-car wreck. And when it comes to weather, most want the same sort of thing - hurricanes, tornadoes, severe thunderstorms, floods, blizzards, record highs, bitter cold and fierce winds.

Sometimes, though, there isn't much bad weather to talk about. Personally, I like that! It makes the day go a little easier, and good weather means I can get outside and enjoy it! More on that later. If there was ever a time when good weather abounds, it's early fall. We often see lengthy stretches of dry, pleasant weather at this time of the year - day after day after day of sunshine by day, and clear, cool to chilly conditions at night.

Why is that? Quite simply, it comes down to a matter of stability. The jet stream is still fairly far to the north, only beginning to expand southward and show signs of moving from its mean summer position toward a much farther south track in the heart of the winter season. And as such, the air aloft at this time of the year is still warm, having the 'memory' of summer, if you will. Meanwhile, in the wake of any strong cold front, a fresh, dry, cool air mass moves in from some higher latitude, with high pressure often building in, such as we see now in the vicinity of the Great Lakes.

When you put the these two things together, you create a very stable environment - cool on the bottom and warm on top. Furthermore, the sinking air associated with high pressure often creates temperature inversions - a discontinuity of sorts in the atmosphere, where the normal way of seeing the air temperature lower with increasing altitude is suddenly and dramatically reversed at this temperature inversion. Temperatures suddenly warm in a short vertical distance at this inversion before returning to the normal way of things farther up. This is a very stable profile and one that you would seldom be able to get something like a thunderstorm out of. If there's sufficient moisture in the lower part of the atmosphere underneath the inversion, you'll see a lot of clouds trapped underneath the inversion, and even some light precipitation of the moist layer is thick enough.

On the weather map today there are two large surface highs - one over the eastern Great Lakes into southwestern Quebec. Underneath this high, the air is plenty dry.

Temperatures in the 30s and 40s were widespread throughout the interior Northeast and mid-Atlantic states back into the Ohio Valley, the Great Lakes and parts of the Midwest. Yet with plenty of sunshine, most places will reach well into the 60s and 70s this afternoon, pretty typical for the last week of September.

Since there is an upper-level and surface storm just east of New England, this surface high is more or less blocked from moving east, as would typically be the case. Here's what that will look like tonight:

The feature sliding away from the Mississippi Valley into the Tennessee Vally is being forced around this block, and as a result of that, the high over the Great Lakes doesn't budge tomorrow. Even on Thursday, it is still going to be there, with any escape route to the East completely blocked still. It will slowly expand southward late this week, as the features bringing unsettled weather through the South and across the Southeast finally move off the Southeast coast and allow the drier air to expand southward. The end result is a multi-day stretch of really fine early autumn weather, with the biggest problem being fog that forms in the valleys each night.

The other surface high is much farther west. After moving on to the West Coast yesterday, it is now in the central and southern Rockies, promoting bright sunshine there. Of the two highs, this one will get erased much more quickly, as the strong upstream trough dives into the West tonight and tomorrow. The trough will bring with it some rain, mountain snow and much cooler air. However, as the trough swings through the Rockies then up across the Plains, it will allow a much stronger high to build into the Rockies behind it, all the while the one in the East still isn't budging! Here's the GFS surface map forecast for Saturday evening:

At that point in time, there won't be much adverse weather anywhere in the country, as the high will hold court across the country!

I mentioned earlier my love of nice weather and how it relates to being outside to enjoy things like bike riding. A couple of weeks ago I ventured up to southern New England, taking a crew from Happy Valley up to participate in The Flattest Century in the East. It turned out to be a perfect weekend for riding! The day of the event, Sunday, Sept. 8, started out a little cloudy, as you may be able to detect as we head toward the registration tables:

It was fun day to ride, and the sun was fully out as we reached Horseneck Beach to snap a few pics of the Atlantic Ocean while the bikes got a break from us being on them!

Of course, the best parts were finishing and seeing the culmination of three months of training of one of my co-workers from no road bike to a first century ride (completed) ever! Next up for me is to let myself be coached toward a much harder endeavor - that of an ironman! Not sure if I'll do the half or the full yet, but I'm about to hand myself over to be trained for the next 11 months. I just hope I get a day like that one on the day of the event, or like one many will see in the East into the weekend thanks to the sprawling high pressure area.

Yes, it may be boring weather for some, but I'm good with that!

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.