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Saturday, July 20, 2019

Barry, then humidity... but a "fall" front is right around the corner!

It's been a fairly wild weather week in the Mid-South. First we dealt with the remnants of "just briefly" Hurricane Barry, which moved across western AR as a tropical depression then sliced into southern MO and headed east into the Mid-Atlantic. Rainfall totals were generally in the 4-6" range from Saturday through Wednesday in the Memphis metro.

Total rainfall from Barry. Generally 4-6" fell in the Memphis metro. (WeatherBell)
As soon as the clouds moved out, the heat built back in as a high pressure ridge took over where Barry left off. The heat, combined with the remaining moisture from Barry's rainfall, resulted in a string of days with Heat Advisories and Excessive Heat Warnings as heat indices climbed into the 105-112° range!


It wasn't the heat, it was the humidity...

In actuality, the humidity was the back-breaker during this week's heat wave. High temperatures were right at normal for July (lower 90s). But typically dewpoints are in the lower 70s and we had dewpoints in the mid to upper 70s, and even some 80° readings, after Barry departed! This made the typical "heat" more dangerous as it was much harder for the body to cool due to excessive moisture in the air. The extra moisture also kept overnight lows warmer than average for summer, which provided less of a chance for cooling (and a much-needed break for our air condition units!).

Daily temperatures for July. Barry's remnants brought cooler temps early this week (blue), but the heat quickly kicked back in late this week (red) with normal highs but very warm lows and very humid air to boot! (NWS)

Fortunately, there is an end in sight! (We just have to hold out a couple more days!)


Rest of this weekend

This weekend will continue the mid/late-week pattern as highs continue to reach the lower 90s and dewpoints remain in the mid 70s. Look for heat indices to peak in the low to mid 100's this weekend. However, there are also small rain chances each afternoon, which might provide some temporary relief for some. For today, the chance is 20% with most afternoon pop-up showers or storms in northeast MS. Sunday will see slightly better chances at 30% for the metro.

The NAM3 model forecast radar from noon Saturday through 7pm Sunday shows a few showers possible Saturday afternoon and a slightly better chance Sunday afternoon. The best chances are southeast of the metro. (WeatherBell)

Monday cold front (hooray!)

Early next week, an anomalously cool and dry airmass (for summer) will push south into our region and hang around for much of the week ahead. On Monday, the cold front preceding this early fall-like high pressure system will move through, bringing with a a high likelihood of  showers and thunderstorms, as opposing air masses collide.

A few strong storms are possible Monday afternoon, though the Storm Prediction Center currently does not have the metro in a severe weather risk. Best chances of rain are Monday afternoon through early evening, though some showers Monday morning are also possible. It'll still be a muggy day but highs should remain in the mid to upper 80s.

The same NAM3 model forecast radar for Monday, from midnight through 7pm. Much higher rain chances, and some storms, appear Monday afternoon as the front arrives. (WeatherBell)

Tuesday-Thursday - an early taste of fall?

Tuesday morning is when we'll first notice the new dome of high pressure as we step outside in the morning to temperatures in the 60s - the coolest in a month. Even better, highs will only be in the low 80s Tuesday afternoon! This lovely pattern continues Wednesday and Thursday with abundant sunshine, low temperatures in the mid 60s and highs in the mid 80s, and low humidity levels.

The European model showing dewpoints from Sunday at 7pm through Wednesday at noon. Notice the high values (deep oranges) slide south and get replaced by dewpoints in the 50s (blues) behind Monday's front! (WeatherBell)

In other words it'll feel more like mid to late September than late July! Perfect weather to kick off the World Golf Championship - FedEx St. Jude Invitational with most of the world's best golfers in town!




Next weekend

By next weekend, as the beautiful dome of high pressure shifts east, southerly wind will start to bring summer back with chances of afternoon thunderstorms and a more typical temperature regime. But at least we will have gotten a nice reprieve after dealing with plentiful rain, then plentiful humidity and heat!

Erik Proseus
MWN Meteorologist

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