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...



Monday

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)


Tuesday

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)


Wednesday-Friday

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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Sunday, September 12, 2021

Humidity & rain chances return as T.S. Nicholas moves towards southeast TX

Much to my chagrin, and probably most of yours, the cooler mornings and below average humidity of this past week is on its way out for the coming week. High pressure to our east brings a return of near-70° dewpoints on light southerly flow, as well as an increase in shower and thunderstorm chances for the coming week. Let's dive into the details.

Monday-Tuesday

With wind shifting to the south today, moisture is starting to increase again after a very pleasant week gone by. Dewpoints - which were in the 50s for much of the past week - will rise to the upper 60s to near 70 degrees to start the week. Ick. Moisture aloft also increases, and that means more scattered to broken cloud cover, especially during the daytime hours. While most of us stay dry, I expect to see a few echoes on radar by Monday afternoon as instability rises a bit. Tuesday will features a few more showers than Monday, but rain chances are still likely to only be 10-20% each day. High temperatures will be in the upper 80s Monday and mid 80s Tuesday with lows in the low 70s instead of the 50s and 60s of the past several days. You'll notice that as you step out in the mornings.




Wednesday-Thursday

As a front moves south towards the region but stalls near the KY/TN border, atmospheric moisture increase continues into mid-week, mainly sourced to our south where brand-new Tropical Storm Nicholas (currently making its way towards the TX coast; see below) will likely be in the vicinity of eastern TX. Southerly wind will push clouds and increased rain chances into the area, though with the main focus of the storm well to our south, I don't expect rain-outs locally. We'll put POPs (probability of precipitation) in the "scattered" range, or 40-50%. Rainfall totals will be insufficient to completely overcome the recent dryness, likely less than an inch in any one spot.


Additional cloud cover will hold highs back to the mid 80s with morning lows near or just above 70° and dewpoints lingering around 70° as well. It'll feel fairly sticky and you'll want to keep the umbrella handy. Forecast confidence dips just a bit for this mid-week period, depending on the eventual track of Nicholas, though it's likely to remain well to our south.




Friday into next weekend

Remnants of Nicholas may dry up a bit to our south due to a lack of flow to push it somewhere else. Meanwhile, high pressure rebuilds a bit over our area, so the Mid-South will probably see diminishing rain chances into next weekend, though maybe not totally dry. High temperatures start to rise back to near 90 degrees with humidity sticking around without a frontal system to shove it away. Overall, for the last weekend of "official summer," you'll probably be ready for fall to arrive for good. We're not quite there yet! 

The temperature outlook from the Climate Prediction Center for next weekend into the start of the following week paints a warm picture. There is a very high probability of above average temperatures for our area, during a time when average highs are in the mid 80s. 

If you are heading to the Mississippi State/Memphis football game on Saturday, it won't be hot chocolate or long sleeve weather yet - plan on a bit of sweat, even just as "engaged bystanders" in the stadium!

Erik Proseus
MWN Meteorologist

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Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: MemphisWeather.net on the mobile web or via the MWN mobile app
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!
MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder