Autumnal equinox begins tilt away from sun in Northern Hemisphere

Summer still reigns supreme here in Mid-Missouri, as temperatures hover around 90 degrees.

While this has been the last trend for the last several days, which is nearly 15 degrees above average, it is only two degrees above-average for the entire month of September. In the coming days the summer temperatures will be challenged as a strong cold front tracks through the Midwest.

It’s the start of what will be a cooling trend that will carry through the rest of the year. This doesn’t mean there won’t be anymore abnormally warm days, it just means that the northern hemisphere is beginning the tilt away from the sun. This brings shorter days and longer nights, along with cooler weather.

So what is the autumnal equinox, and when did it take place? The autumnal equinox marks the point at which the sun is directly over the equator, the start of fall in the northern hemisphere and spring in the southern hemisphere. It also marks equal day and night for those along the equator. There is a common misconception that everyone on earth experiences 12 hours of daylight and night during the equinox, but that’s not entirely true. Because of the atmospheric refraction of sunlight and the way sunrise and sunset are defined, many places don’t see equal day and night until a few days after the autumnal equinox. This year, the autumnal equinox occurred on September 22 at 3:02 CST, which means Saturday was the first full day of fall.

From now through the rest of the year, the northern hemisphere will spend its time tilted away from the sun. This tilt means less solar radiation and cooler days. Those cooler days start next week when a strong cold front rolls through the Midwest. It’ll go from above-average temperatures to below-average temperatures and little to no humidity. It’s a true testament to fall with sunshine, low humidity, and cool nights followed by pleasant afternoons.

Lately that hasn’t been the case, as a rather impressive upper level ridge has set up shop across the eastern half of the country. This has led to the warmer temperatures, with the extended summer afternoons. In the western portion of the country a trough has been digging in the Pacific Northwest, it’s this trough that will drive our weather over the next week.

As Sunday approaches, the large upper level ridge will finally shift off to the east. This will put Mid-Missouri on the western periphery of the ridge. Aloft there will be a weak upper level disturbance that will round the ridge and bring a chance for some nonsevere afternoon showers and storms. From Sunday through the middle of next week a front will gradually track into Mid-Missouri and bring an increased chance for showers and storms. Most of the activity holds off until Tuesday, but it’s not looking impressive when it comes to rain accumulations. For now it’s looking like Mid-Missouri will see anywhere from a tenth of an inch to half an inch of rain by Wednesday morning.

From the middle of next week and on into the weekend, cooler temperatures will be more pronounced. By this time next weekend temperatures will struggle to make it into the lower 70s. Just be sure not to overindulge on the pumpkin spice lattes as temperatures continue to fall.

For continuing coverage on the fall outlook and what to expect as we head into severe weather season you stay tuned to ABC17news.com and follow us on Twitter @ABC17Stormtrack.