Above average heat forecast to continue through next week: SW MS Weather Forecast – 6/17/2022

Good morning! Hope you all haven’t become sick of the above-average heat just yet, because it sure does look like it is going to stay for a while…

Currently, a stubborn mid-level ridge is parked over the southeastern half of the United States, with the center somewhere around Northern Arkansas and Southern Missouri. What this means is that the anticyclonic flow around the ridge is forcing large amounts of moisture from the Gulf of Mexico onshore, circling around the ridge, and creating somewhat of a bubble of sticky, humid air across the Southeast.

In fact, according to the SPC Mesoscale Analysis page, at the time of writing this article (10:00 pm Thursday), the precipitable water values – which are a measurement of the amount of water vapor in the air – are over 1.8″ for all of Mississippi, with some parts of Western Mississippi surpassing the 2″ mark! There’s certainly no doubt that this air is humid…

It’s not just the humidity that makes it feel muggy outside, however. Temperatures this week have been well into the 90s F, leading to heat index values over 100 F. In fact, yesterday, with a temperature of 97 F and a dewpoint of 75 F, the heat index at Jackson got to 110 F between 4-5:00 PM before a thunderstorm moved in and cooled things down.

So, is this muggy weather going anywhere? If you’re looking for the short answer, then it’s no, as both the GFS and the ECMWF models depict anomalously high 500mb geopotential heights through the end of next week.

However, if you’re looking for a longer answer: It is still no.

But there is at least the chance for some relief come Sunday. As an upper-level low continues to moves eastward from the Great Lakes to the Northeast, and another upper-level moves onshore in the Pacific Northwest, the ridge that has been dominating the weather in the South recently is forced to wobble westward for a bit over the weekend as it is pinched between these two upper-level lows.

Now, with the mid-level flow directed from the north instead of from the east-southeast like the past few days, some notably drier air can work its way into Southwestern Mississippi for Sunday. One interesting feature about this drier air is that it’s actually a gift from our neighbors to the North. As shown from the NOAA HYSPLIT model, the dry air arriving on Sunday can be traced back all the way from the territory of Nunavut in Northern Canada!

Unfortunately for us, however, this air originated from more than 3.5km (11,500ft) above the ground, and during its journey to Southern Mississippi where it will sink toward the surface, it will undergo a process called compressional heating – this means that, despite this airmass coming all the way from Northern Canada, Sunday will still be hot with temperatures in the low-to-mid-90s – regardless, the lower humidity will still be a nice relief. As a matter of fact, precipitable water, which if you recall is currently around 2″, will fall to as little as 0.5″ Sunday afternoon, almost 3 standard deviations below average! This shot of much drier air will result in dewpoint temperatures in the 50s.

As has been alluded to in previous forecasts, the dry weather doesn’t stay for long. By Tuesday, the mid-level ridge will drift back over the Southeast, restarting an east-southeasterly flow that will draw moisture from the Gulf of Mexico back into the region, causing dew points to rise back into the 70s F.

Aside from the brief respite from the perpetual muggy weather on Sunday, there are a few chances of relief in the form of afternoon storms. While Friday looks mostly dry, Saturday evening into Sunday morning has a greater chance for some unsettled weather as some enhanced 500mb vorticity advects in from the north.

Apart from this, the generally weak low-level synoptic flow courtesy of the high pressure will support at least the chance for a scattered afternoon thunderstorm developing along converging sea-breeze boundaries through the remainder of the forecast period.

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Day-to-Day Forecast

Friday
Partly cloudy skies with a 20-percent chance of an afternoon shower or thunderstorm. High temperatures in the mid-90s are likely with heat index values approaching 105F; overnight lows in the mid-70s are expected.

Saturday
Partly cloudy skies with a 60-percent chance of an evening or overnight shower or thunderstorm. High temperatures in the mid-90s are likely with heat index values approaching 105F; overnight lows in the mid-70s are expected.

Sunday
Less humid. Mostly sunny skies with high temperatures in the mid-90s and overnight lows around 70F.

Monday
Mostly sunny skies with high temperatures in the mid-to-upper 90s with heat index values approaching 105F; overnight lows in the low-to-mid-70s are likely.

Tuesday
Mostly sunny skies with a 20-percent chance of an afternoon shower or thunderstorm. High temperatures in the mid-to-upper 90s with heat index values around 105F; overnight lows in the mid-70s are likely.

Wednesday
Partly cloudy skies with a 20-percent chance of an afternoon shower or thunderstorm. High temperatures in the mid-to-upper 90s with heat index values around 105F; overnight lows in the mid-70s are likely.

Thursday
Partly cloudy skies with a 20-percent chance of an afternoon shower or thunderstorm. High temperatures in the mid-to-upper 90s with heat index values around 105F; overnight lows in the mid-to-upper 70s are likely.