Heavy Rain, Flooding Possible For Lower Mississippi Valley, Southern Plains

Jon Erdman
Published: October 20,2015

A number of ingredients in the large-scale weather pattern are coming together the next several days to fuel a threat of heavy rain and flooding in the south-central United States. This potentially excessive rainfall could even cause flooding in areas where drought conditions have worsened in recent months.
Moisture and energy from Tropical Storm Patricia in the eastern Pacific and a tropical disturbance near the Mexico's Yucatan Peninsula may also add more fuel to this soaking scenario.
Below are the details on the heavy rain threat and how the tropics may be involved.
(MORE: Expert Analysis | Hurricane Central)

Heavy Rain, Flood Threat in the Southern Plains

Persistent southeasterly winds will pump moisture from the Gulf of Mexico into the southern High Plains by Wednesday, where it will interact with an area of low pressure forming aloft over the Southwest. This will contribute to heavy rains as far west as eastern New Mexico, western Texas and western Oklahoma by Wednesday night and Thursday.

Southwest Upper Low

This rain will then spread across the rest of Texas, Oklahoma and possibly parts of Louisiana and Arkansas by Thursday night or Friday. A separate weather disturbance moving through the southern tier of the U.S. will prolong the heavy rain threat into this weekend across those states.

Forecast Next 5 Days

In addition, moisture and energy from Tropical Storm Patricia in the eastern Pacific could be involved in this setup. Computer forecast models are showing that after it makes landfall in Mexico as a tropical storm or hurricane, the mid-level remnants will get pulled northeastward into the south-central states by a southward dip in the jet stream over the western and central United States.
(MORE: Tropical Storm Patricia Forecast to Strengthen)
In all of the above mentioned areas, flash flooding is possible where heavy rain persists the longest. However, small-scale details will dictate exactly where this threat will be the greatest in the coming days. Our rainfall forecast map shows that a widespread area of the southern Plains has the potential to see 3 or more inches of rain through this weekend. Some areas may pick up 6 inches or more of total rainfall.
Flash flood watches have been issued by the National Weather Service for parts of southwest Texas and eastern New Mexico.
In addition, persistent onshore winds may lead to some coastal flooding, high surf and rip currents this week along the Texas Gulf Coast.
Coastal flood advisories have been issued for portions of the Texas and Louisiana coasts.
(FORECASTS: S. Padre Island | Corpus Christi | Houston | Lake Charles, Louisiana)

Rainfall Outlook

This rain is needed to help a relatively rapidly-developing flash drought, which set in over the southern Plains and Lower Mississippi Valley from mid-summer on.
(MORE: Drought Has Returned Again)
The heavy rain threat, while squelching the recent wildfires, may be too much of a good thing in these areas, instead triggering flash flooding. It's also possible some of the drought area may see little or no rain at all from this setup.

Watching the Western Gulf and Eastern Pacific

A broad area of thunderstorms has been percolating near Mexico's Yucatan Peninsula the last several days.
Since this weekend, the National Hurricane Center has been highlighting this area at times for a low chance of development into a tropical depression or storm over the western Caribbean Sea or the southwest Gulf of Mexico.
(FORECASTS: Cancun | Cozumel)
Even though the chance of development is low, we'll continue to monitor future satellite and computer model trends in the days ahead to see if there are any changes.
Right now, unfavorable winds aloft are in place across the Gulf of Mexico due to the subtropical branch of the jet stream. This wind shear is a common nemesis of both developing and active tropical cyclones and has played a significant role already with several named storms this hurricane season.
A second area of interest in the eastern Pacific has formed into Tropical Storm Patricia. As mentioned before, moisture from this system may get pulled into the southern Plains by this weekend.

MORE: Retired Atlantic Hurricanes