Texas, Oklahoma could go from drought to deluge in a week's time
It's been a summer full of extreme heat and prolonged drought in Texas and much of Oklahoma, but a needed change in the weather pattern is on the way as temperatures are forecast to throttle back this week. While there is some good news that rain is forecast for parts of the region, too much rain is likely to cause flooding in some areas, AccuWeather meteorologists caution.
"A strong bubble of high pressure at most levels of the atmosphere has kept rain away and caused heat to build much of this summer over the south-central United States," AccuWeather Chief On-Air Meteorologist Bernie Rayno said. "But change is on the way."
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Wednesday brought the last 100-degree day in Dallas for the foreseeable future, and there is a remote chance that temperatures may struggle to hit 100 again for the rest of the year in the north-central Texas metroplex. This may especially be the case if the metro area as well as many other locations in northern and perhaps parts of central Texas are hit with drenching rain in the days ahead, forecasters say.
Dallas has tallied 47 days with highs of 100 or greater so far this summer through Aug. 18. This past July alone brought 27 days of 100-degree heat and was second only to July 1980, when every day of the month hit 100.
Similar to Dallas, Oklahoma City will get substantial relief from the heat this week. Oklahoma City had 18 days of triple-digit highs in July and six more in August, even though rainfall has been a bit more frequent in the state when compared to much of Texas. Highs will be in the 80s most days through next week with a couple of exceptions.
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"As a front begins to dip southward over the southern Plains and Southeast states, the heat dome that has been so prevalent this summer will break down and allow the number and frequency of thunderstorms to increase," Rayno said.
The Dallas/Fort Worth area was hit with drenching thunderstorms that left up to 2 inches of rain on Wednesday night. The torrential downpours triggered localized flooding. A week earlier, thunderstorms dropped up to 2 inches of rain on the region as well.
Once the ground is moistened, temperatures are likely to have a tough time reaching extreme levels as more of the sun's energy is gobbled up in trying to evaporate that water in the ground. Another factor is that the sun angle decreases in August as daylight hours grow progressively shorter.
With a few exceptions, "temperatures will trend to near average during the second half of August, instead of 5-10 degrees or more above average which has been occurring much of the summer," Rayno said.
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Highs in the 100s and upper 90s in much of northern Texas and Oklahoma through midweek will be swapped with highs in the lower 90s and even the 80s in some cases through next week.
The heat is also likely to ease farther south in Houston (high of 99 F Wednesday), Austin (high of 101 F Wednesday) and San Antonio (high of 97 F Wednesday), as well as areas farther west in San Angelo, Abilene and Lubbock, Texas.
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Highs in the upper 90s to near 100 will be replaced with highs within a few degrees of 90 and opportunities for thunderstorms around Houston starting late this week. Abilene, which is experiencing its driest summer on record and has recorded a temperature departure of 5.1 degrees above average since June 1, will also be in the path of more frequent storms in the days ahead.
"Most droughts in Texas end in floods, and that is possible in a very isolated fashion on Friday and perhaps in a more widespread nature late this weekend and early next week in portions of the northern and central parts of the state," Rayno said.
Contributing factors for the expected increase in downpours for part of the south-central U.S. include an expansion or eastward shift in the North American monsoon pattern, a northward surge in moisture from the Gulf of Mexico and a southward dip in the jet stream.
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The biggest and most widespread rainfall is expected to occur from Sunday to Monday of next week.
"Exactly where a west-to-east band of showers and thunderstorms sets up will determine if heavy rain targets more of Oklahoma or more of central Texas," Rayno said. "Given steering winds will be from the northwest and that Texas will be closer to Gulf of Mexico moisture, portions of northern and central Texas are probably most likely to be hit with the bulk of the downpours," he added.
There is the potential for a few inches to perhaps a foot of rain to fall in the zone from northern and central Texas to Oklahoma and parts of Arkansas and Louisiana over the next five to seven days.
There is a significant chance that showers and thunderstorms will drench some locations for hours and perhaps a couple of days. This is known in the weather community as a "training effect," and it has caused major flooding problems in the past. More recent examples of this include the deadly flooding in St. Louis and portions of Kentucky during late July, where 6-12 inches of rain poured down in a matter of hours.
AccuWeather forecasters say a potential wild card will be the track and strength of a tropical disturbance that will enter the southwestern Gulf of Mexico on Friday. There is a chance that showers and thunderstorms from this system, even if it remains poorly organized, could reach southern parts of Texas next week. South Texas and the Rio Grande Valley received 5-10 inches of rain in recent days as a tropical rainstorm rolled in from the Gulf of Mexico.
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