More High Pressure!

There are a few hallmarks of being in the seasonal transition period when it comes to weather. In the early stages of autumn, it's not uncommon to see large daily temperature variations, especially when under the influence of high pressure like we are now. Cooler air continues to reside over us during the night, but with the sun's angle in the sky still somewhat direct, it doesn't take long to quickly warm up during the morning hours. This can lead to a temperature spread of 30°+. Indeed, that was the case today. The mesonet site on the north side of Bowling Green recorded a low of 49° this morning, but unimpeded sunshine brought the mercury all the way up to 84° this afternoon. That's a range of 35°! You may have reached for a sweater when departing for work or an early class, but t-shirts were needed by the PM hours.

This visible satellite image from 4:15 PM this afternoon reveals what little cloud cover we had today. These high-level clouds didn't stick around long.

Another phenomenon during the transition period is a resurgence of severe weather for a short time, commonly known as the "second season". Obviously, the most active stretch of severe weather is in the spring, when the jet stream lifts northward from it's winter hibernation over the subtropics. This results in clashing air masses, genesis of low pressure systems, and boom . . . severe weather. OK, so that's a generalization but it is a large part of the process. Sometime during autumn, the reverse happens. The jet sags southward after ridging out in Canada for much of late summer, and we get a similar chain of events.

This is mainly just free trivia, as there is no threat for severe weather in our forseeable future. The SPC does happen to be eyeing a possible threat for late next week over the central Plains, but this is way out in model territory. Major confidence in severe weather forecasts doesn't present itself until about three days from the anticipated event. Right now, these developments are worth monitoring but it's haphazard to draw any conclusions more than a week away. All we have to focus on right now is an absolutely massive block of high pressure covering nearly the entire eastern half of the United States. We've been almost completely devoid of cloud cover during the past few days. High pressure has been snuffing out cloud development over the Midwest for a few days now. This pattern will hold strong for a couple more days before it finally begins to break down late this weekend. We'll get an influx of clouds Saturday night into Sunday, and may even see some rain on the backside of a weak low churning out of Dixie Alley.

Tonight: Mainly clear skies with calm winds. Low near 54°.
Friday: A repeat of today. Sunny skies and a high around 83°. Northeast winds around 5 mph.
Friday night: A warmer low of 60°. Mostly clear skies and winds becoming calm.

Have a good evening!
- Caleb Chevalier