Sunday, September 19, 2021

Who's ready for fall? Autumn front arrives Tuesday PM

In the wake of the now-dissipated remnants of Nicholas, a tropical-like airmass sits over the Lower Mississippi Valley into the southeastern U.S. that has led to daily showers, some heavy, and a few thunderstorms each of the past few days. This pattern will stick around another day before the first significant fall cold front arrives just in time for the autumnal equinox! Let's hit a few details...


The start of the work week brings more rain chances, though they appear to be a bit lower than the past few days. Scattered showers and thunderstorms are possible throughout the area during the day, but appear to be most likely east of the Mississippi River. With warm, and muggy air around, and fewer showers than past days, temperatures will rebound into the mid 80s with partly sunny skies in the afternoon. A south wind keeps dewpoints in the lower 70s - which is where they have been the past week.

The HRRR model forecast radar for Monday shows most precipitation remaining east of the metro. Remember, models aren't gospel and we think there could be some scattered activity further to the west, but it won't be as wet as the past few days. (WeatherBell)


Cold front day! We'll start the day with warm and muggy conditions, but it won't take long before the wind shift associated with the front arrives around mid-day. That will trigger scattered showers and thunderstorms once again, with fairly high rain chances lingering into the afternoon and evening. Highs will again reach the mid 80s, and could begin falling by mid-afternoon. Overall, rain amounts Monday and Tuesday are likely to average in the 0.5"-1.0" range with locally higher amounts where multiple heavy showers or storms move over. Drier air associated with the front won't get here until Tuesday night, with a push of cooler air arriving on gusty north wind. 

The effects of the fall front can be seen in this forecast of dewpoints on Tuesday. Humid air will be shoved away by north wind that brings much more comfortable conditions. (WeatherBell)

This loop shows total atmospheric moisture from Monday evening through Friday and also clearly shows the arrival of drier air behind the front. Very moist air (yellows to reds) is displaced by the dry air (in purple to brown) behind the front. (WeatherBell)


Fall officially starts at 2:20pm Wednesday and it'll certainly feel like the seasons have changed! We'll wake up to temperatures near 60 degrees. Despite sunshine all day, high temperatures will only reach the mid 70s on a dry north breeze. With that dry air in place, dewpoints will fall into the 40s (FORTIES)! That is dry enough to break out the hand lotion. Thursday and Friday will feature abundant sunshine, morning lows in the 50-55 degree range and afternoon highs in the mid to upper 70s. A simply stunning end to the week and welcome change!

First weekend of fall

...will feel like it! Another front may graze the area Saturday, but with no more than a few clouds. It will keep things dry throughout the weekend and into early the following week. While temperatures will start to slowly rebound to near average levels, lows will still be in the 50s to near 60 and highs in the lower 80s. With dewpoints remaining low, it will be a comfortable 80 degrees in the afternoons. Should be beautiful weather for football Friday night and Saturday afternoon at the Liberty Bowl. After Tuesday, no rain is in the forecast for a week. Enjoy!

The temperature outlook from the Climate Prediction Center for the end of September indicates a good chance of below average temperatures. (NOAA/CPC)

Erik Proseus
MWN Meteorologist

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