Monday, September 21, 2020

Fall arrives Tuesday -- astronomy and meteorology agree!

Welcome to Fall!

The autumnal equinox occurs Tuesday morning at 8:30am. In this case, the weather forecast is right in line with astronomy, as generally pleasant conditions are occurring as the Earth begins to tilt away from the sun and pass the Equator from north to south (the latter of which explains why winter season is cooler than summer in the northern Hemisphere).

It's been a dry month overall with only a couple of major rain threats and officially less than 1/2" of rain at the airport three weeks into the month. That dry streak will hopefully come to an end this week, as yet more remnants of a tropical system move towards the Mid-South (appropriately enough, #2020). While the sunshine, cool mornings, and pleasantly warm afternoons of the past several days have been great, clouds will obscure the sky more often than not over the next several days and rain chances tick up, particularly Tuesday night through Thursday. 

Tropical Storm Beta is making landfall tonight as a disorganized and very slow moving tropical storm over the middle Texas coast near Matagorda Bay, or roughly midway between Corpus Christi and Houston. Once it reaches the coast, a sharp turn to the northeast will result in the storm inching along the shoreline towards Houston, dumping several inches of rain along the way. By mid-day Wednesday it will be near Galveston Bay then start to accelerate into Louisiana, then turn northeast and move across Mississippi Thursday night into Friday as it dissipates. 

Our best chances of rain locally will be as precipitation lifts well northeast of the system into the Mid-South starting Tuesday night and continuing Wednesday and into Thursday, particularly during the morning hours. However, no all-day rain events are really expected and rainfall totals likely will average around an inch through Thursday with higher amounts, possibly up to 2 inches, across section of north MS. So though it won't be a lot, an inch of rain would be welcome at this point! 

Total precipitation as forecast by the NWS through Thursday evening. (WeatherBell)

As for temperatures, the cloud cover and easterly wind the next few days will help to hold high temperatures well below average (which is in the low to mid 80s). Look for highs on Tuesday in the lower to mid 70s. On Wednesday, with scattered showers, temperatures will struggle to even reach 70 degrees, remaining in the 60s most of the day! The last time we saw daytime highs that cool was mid-May! Overnight lows will bottom out near 60 each morning. 

As we head towards the weekend, look for a general drying trend with lingering spotty showers and a bit more sunshine by Saturday and Sunday. Highs rebound to 80+ while lows remain in the 60s as high pressure briefly builds in. Another front on Sunday looks to undercut temperatures once again heading into next week. Outside of a very unlikely, short-lived hot day, it appears we may be done with ninety degree temperatures for 2020 - but don't hold me to it just yet! In the meantime, enjoy the changing of the seasons, cooler temperatures, and your pumpkin spice lattes!

Erik Proseus
MWN Meteorologist

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