Extreme Heat and Humidity to Impact Much of the Southern U.S.

Quincy Vagell
Published: August 7,2015 




 

On the heels of a hot finish to July across much of the southern U.S., another string of hot days is underway way. In many spots, the heat will only worsen this weekend.

Three-Day Forecast Highs

 Widespread highs in the upper 90s to 100s are in the forecast for portions of the southern Plains and Lower Mississippi Valley through this weekend and should last into early next week. As of Friday morning, roughly 18 million people were under heat advisories or excessive heat warnings. Many more heat-related advisories can be expected in the coming days. 

If 100-degree heat was not bad enough, high levels of humidity will make it feel even more uncomfortable.

Forecast Feels Like Temperatures

With dewpoints forecast to remain in the 70s for several days, the heat index – or the temperature it feels like when you factor in the humidity – is forecast to rise to near or even above 110 degrees in many locations by this weekend. The hardest hit areas look to be across Oklahoma, Texas, Arkansas, Louisiana, Mississippi, Alabama and western Tennessee.

Little relief is expected at night as cities like Memphis, Tennessee, and Jackson, Mississippi, may struggle to fall below 80 degrees for low temperatures by Sunday and Monday.

(MAPS: 10-day Forecast)

While some daily record highs may be broken, the bigger story may be the longevity of such hot conditions. Shreveport, Louisiana, did not hit 100 degrees even once in 2014, but they have already reached 100 degrees 10 times this summer. This includes a stretch of 10 out of 13 days from July 24 to Aug. 5. 

The hot weather will be associated with a ridge of high pressure in the upper levels of the atmosphere. This ridge is projected to be centered right over southwest Arkansas. However, it will influence a broad area of the South with sinking air motions that suppress thunderstorm development. This will deflect most rain and thunderstorm activity to the north, meaning much of the period will not only be hot, but short on rainfall as well.

Rainfall is one thing several Texas cities saw none of in July. The city of Tyler, Texas, marked its first rainless July since continuous recordkeeping began at the airport in 1984. Longview and Waco each had their first rain-free July since 1993. Monroe, Louisiana, just experienced one of its top 10 driest months of July on record.

(FORECASTS: Dallas, Texas | Baton Rouge, Louisiana)

Even locations very close to the Gulf Coast, including southern Louisiana, can expect to feel the effects of the oppressive heat and humidity. Being east of the high-pressure center means winds will tend to blow from the north. While that's a cold wind in winter, it's a wind blowing off sun-parched land in summer and preventing the moderating effects of the Gulf of Mexico from having as much of a cooling influence.

Some relief is possible by the second half of next week as some forecast models shift the ridge to the west, taking the hottest of the hot air with it.

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