Thursday, May 27, 2021

Stormy lead-in to a fabulous holiday weekend

The heat and humidity has built this week with spotty precipitation over the past couple of days. High temperatures have generally been near 90 degrees, though as of early Thursday afternoon we had yet to actually reach 90 degrees yet this year. Looking ahead to the Memorial Day holiday weekend, fabulous weather is on tap - low humidity, cool mornings, pleasant afternoons and sunshine! However, we'll first need to deal with a late spring cold front...

Storm chances the next 24 hours

With unstable and humid air in place ahead of a cold front that arrives on Friday, the ingredients are in place for thunderstorms, and those will affect us over the next 24 hours. There are multiple small-scale (or "mesoscale") atmospheric features that are affecting thunderstorm development well to our northwest today - chiefly over the central plains. The development and propagation of those storms will determine when we see storms in the Mid-South, which makes pinpointing the timing somewhat complex. In addition, the timing of the arrival of those storms will also factor into the risk of severe weather. 

Our best educated guess at what to expect is that an initial wave of thunderstorms will move into the area late this evening, most likely after 8-9pm. Models hint at these mainly affecting northern AR and western TN. The Memphis area may be on the tail end of this cluster or line. After what should be a lull of perhaps a few hours, a more substantial threat of storms arrives in the wee hours of Friday morning. The exact timing is again in some doubt, but most model sets suggest that they will roll through at some point between 2-3am and morning rush hour. These storms, due to their timing in the "coolest" part of the day (though it will still be relatively warm and muggy) will likely be weaker when they arrive than when they are moving across AR during the overnight hours and should mostly fall apart as they shift east of the metro. Below is the HRRR model's opinion of how the scenario unfolds, with caveats that it's timing and/or intensity could vary, perhaps quite a bit.

The mid-day Thursday HRRR model showing forecast radar through noon Friday. Model output does not equal gospel. (WeatherBell)

Storm threats and preparation

Our main threats with any severe weather would be strong wind gusts due to the expected linear nature of the storms - in other words a squall line, though weakening. Minor flash flooding or small hail are also possible. The tornado threat appears minimal. Below is our latest impact graphic. Best ways to prepare include tying down anything that might blow away in strong wind and garaging vehicles if able. After a fairly long dry spell, the ground should readily accept most water than falls with little issue as rainfall will average under an inch.

A Memorial Day weekend to remember!

Speaking of the weekend ahead, we'll have quite a nice few days to spend outdoors without too much sweat! Overnight lows behind the cold front are expected to dip into the mid 50s with highs Saturday and Sunday in the 70s! We'll warm up some Monday, but still should feel very pleasant for holiday cookouts. Look for more humidity to build into the middle of next week with daily rain chances by Wednesday.

Erik Proseus
MWN Meteorologist

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