Four things to know about our Labor Day weekend weather

It's been a long time coming, but we've finally got some beautiful weather in the Mid-South! And not a minute too soon... because it's a holiday weekend! If you have outdoor plans this weekend (and who doesn't there's SO much going on), here are 5 things you need to know about our Labor Day weekend weather.

1. The streak is over!

A couple weeks ago we ended lengthy (two-month-plus) heat streaks - one for daily average temperatures over 80° and another for high temperatures above 88°. This morning, the last summer-long warm weather streak came to an end. Until this morning, we had not had an official low temperature in the 60s since June 10. 83 days later, and after breaking the record on Thursday morning set in the scorching summer of 1980, that streak came to a merciful end as the low dropped to 68° at the airport.

2. Early autumn-like dewpoints

The dewpoint (a direct measurement of the amount of moisture in the air) is related to relative humidity, which tells us how "sticky" the air is, and drives things like low temperatures. It's one of two contributors to the heat index (temperature being the other). We've endured dewpoints well into the 70s most of this summer, which is very muggy, and coupled with temperatures in the 90s produces heat indices well above 100. A cold front that moved through Thursday afternoon has brought a nice northerly breeze and forced dewpoints down into the upper 50s this afternoon and it's like a breath of fresh air! These cool dewpoints will stick around through Saturday before starting to rise again Sunday and Labor Day. That will mean cooler low temperature as well, making for very pleasant conditions through Sunday morning. By Sunday afternoon, dewpoints will be rising back through the 60s, which is a little more noticeable but still lower than we have experienced in some time.



Surface high pressure over the Great Lakes is bringing a refreshing northerly breeze and lower humidity into the Mid-South as dewpoints above 70 are suppressed to our south (south of the pink line). (Wright-Weather.com)

3. Upper level trough means cooler temperatures

As you can see from the map above, high pressure is centered over the Great Lakes so it is cooler than high pressure centered over the Atlantic, like the "Bermuda high" that typically dominates our summer pattern. Coupled with the cooler surface high, the upper levels feature a trough of low pressure over the eastern U.S. We expect cooler temperatures under upper level troughs than upper level ridges (of high pressure). With the trough in place (which, coincidentally, has helped steer Hurricane Hermine northeast around its periphery), below average temperatures continue through Saturday with highs only in the mid 80s. As it weakens, temperatures start to rebound on Sunday and we'll be back to near or slightly above average temperatures in the lower 90s for Sunday and Monday.

At the upper levels, low pressure over the Ohio Valley has resulted in a "valley" or trough south of it, which typically signals cooler than normal temperatures. While it won't last long, it is definitely a welcome pattern for a holiday weekend! (PivotalWeather.com)

4. Unfortunately, summer's not necessarily over

Not to be a "Debbie Downer" on this great weekend forecast, but as we head into next week, warmer high pressure at the surface and a ridge aloft will build back into the area as Hermine moves into the western Atlantic. The result? More warm weather and higher humidity, though not to mid-summer levels. Most of next week will feature high temperatures that rise back into the lower 90s with dewpoints in the lower 70s. That's enough to get heat indices back up close to 100°. In addition, a few afternoon thunderstorms will be possible each day, especially the latter half of the week. In the long-term, it looks like another front will move through next weekend (Sept 9-11 timeframe) that will once again cool us back down, hopefully this time out of the 90s for good! Hang in there! Fall is just around the corner, and after the fourth warmest "meteorological summer" (June-August) on record, it can't come soon enough!

And with that, I'll just be going now... Happy Labor Day!

Erik Proseus
MWN Meteorologist

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