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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Saturday, July 13, 2019

Saturday update: Barry's impacts on the Mid-South

Briefly a hurricane, Barry made landfall on the central Louisiana Gulf Coast this morning and is moving slowly north through Louisiana. It will remain over Louisiana through much of Sunday before heading north through central Arkansas west of Little Rock Monday as it weakens to a tropical depression. Unfortunately, that means the weather in the Memphis area will be depressing for a few days as well.

Pictures are worth at least 1000 words each when you're talking about weather, so I'll use a lot of them in this update. First, the latest track from the National Hurricane Center:

And as an overview, below is how the European model handles Barry's movement through Wednesday evening. It has done a very good job of predicting the path of the storm to this point.

Water, water everywhere

The main story for our area will not be wind (though for the Mid-South, it will be more than we are typically used to), but the rain. We'll start there. The outer portion of Barry's main rain shield will move into the metro Sunday morning, maybe before daybreak. However, despite likely being steady, we won't get an unusual amount during the day Sunday. Here's the NWS rainfall total through Sunday at 7pm (it's about half an inch):

Precipitation 7pm Saturday- 7pm Sunday

Sunday night is when the rain really starts to pick up, especially after midnight. We could see a couple inches of rain in some areas. A few thunderstorms are possible as well which could enhance rain totals in spots.

Monday is a continuation on the rainy pattern, though with the center moving by to our west, we could see more banding of rain set up with localized heavy amounts and others getting less. The NWS puts precipitation totals Sunday night through Monday at 7pm above 2" in the metro, heavier to the west, closer to the center of the storm.

Precipitation 7pm Sunday - 7pm Monday

Rain remains likely Monday night as the remnant low moves north into southern Missouri with showers and thunderstorms continuing off and on Tuesday. As the rain is not quite as continuous by Tuesday, a bit more heating could take place and result in more thunderstorms than Sunday or Monday. Precipitation from Monday night through 7pm Tuesday, another 2-3":

Precipitation 7pm Monday - 7pm Tuesday

By Wednesday, the system starts moving east through the Ohio Valley and we get back to a more scattered thunderstorm pattern as highs climb back to near 90. All of the previous rain will mean a muggy environment. After a few days in the 70s and 80s, a heat index near the century mark Wednesday will be an unwelcome reminder that it's still summer. By Wednesday evening, total rainfall amounts from Barry will likely be in the 4-7 inch range. That's a month's worth (or more) in 4 days. Some areas could potentially see 8"+.

Total precipitation expected from Barry through mid-week

For this reason, Flash Flood Watches go into effect Sunday and continue through early Wednesday.

The long duration event means that local rivers will rise and poor drainage areas could be a real issue. We remind you to "Turn Around, Don't Drown!" Avoid areas with water covering the road. Stay away from drainage ditches and high water in creeks, ponds, etc. (and keep your kids away from them too!). If you're in an area prone to flooding, you might consider leaving for a few days.

Gusty wind too

As expected from a remnant tropical system passing nearby, we'll get enough wind for some bad hair days, but probably not a lot of widespread damage. Southeast to southerly wind will be the norm as the low passes by to the west. We'll see gusts Sunday afternoon and evening into the mid 20s to near 30 mph.

Sunday night and Monday will likely be the windiest with gusts routinely into the 30s and some areas seeing 40 mph or higher. Coupled with the soaking rain and soft ground, 40 mph could be enough to topple some trees and maybe affect power to some areas as well. Plan to keep those devices charged and secure anything outdoors that you can Sunday before the wind picks up. By Tuesday, it'll be breezy but nothing we don't see semi-routinely in spring or fall.

Tornado threat

Land-falling tropical systems are also known to spawn a few weak and brief tornadoes in their eastern semicircle well inland. It doesn't take big supercell thunderstorms to initiate these. Heavier showers in bands rotating around the center can encounter just enough instability, and already are in a high shear environment, to spin up weak tornadoes with very little notice. The most likely time that these spin-ups MAY occur is Sunday afternoon and Monday. For this reason, the Storm Prediction Center has placed areas mainly near and west of Memphis in a Marginal Risk (level 1/5) for an isolated tornado Sunday and Monday.

That gives you a pretty good overview of the hazards we could expect over the next several days. Stay with, particularly on our social media channels, and other local sources as we bring you the latest information while Barry moves through the region.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: 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