The first significant cold front of Fall 2016 moved through Alabama yesterday, cooling temperatures from highs in the upper 90s Saturday and Sunday to the upper 80s today. If you look at the chart above, a secondary front, or dry line, is moving through Alabama now, with another wind shift from west to north, and behind this front the dry air moves in. Dewpoints (green) ahead of the secondary front are around 65 (still fairly humid), but behind the front they fall quickly into the 40s, the driest air in Alabama since May! The dry air will make it feel cooler outside tomorrow and then allow nighttime temperatures to drop a bit lower later this week, with 50s likely if the wind calms down.
The overall weather pattern has changed drastically, as we have gone from a ridge of high pressure at upper-levels that we have had for most of the past two months to a big upper-level low that is currently spinning over the Great Lakes. That low will move little, but sag a bit southward, through the end of the week. This will allow another, reinforcing cold front to move through on Thursday, dropping high temperatures into the 70s, with clouds and a breeze, on Thursday and Friday. It will really feel like fall!
Dr. Tim Coleman