Record rains likely in Arkansas, Texas and Louisiana

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Next stop: Southern Plains

In classic El Niño fashion, the Pacific jet stream will dip to uncommonly low latitudes as it move inland. By midweek, the jet will have carved out an upper-level low in northern Mexico (see Figure 3 below). At that point, its progress will be halted by strong upper ridging over the eastern U.S. In between, this will allow for extremely rich tropical moisture to flow northward from the Caribbean and Gulf of Mexico into the lower Mississippi Valley. The amount of precipitable water in this air mass is projected to surpass record levels for March in some areas.

A stationary front expected to lie from Texas toward Illinois will become the focus of multiple rounds of heavy showers and thunderstorms over several days. Some severe weather could emerge, including tornadoes, although the set-up looks less like a prolific twister producer and more like a torrential rainmaker. The focal point is likely to be Arkansas, where the stationary front should be aligned near or just east of the Ozarks. This would help enhance uplift and set the stage for what could eventually pose a serious flooding threat. The 00Z Friday run of the GFS model dumped 8” to 12” of rain over most of the southeast half of Arkansas over the ten days ending on Sunday, March 13. A secondary peak of 8" or more could develop in parts of Louisiana. Such a forecast is quite plausible, given the very moist air mass expected and given the fact that upper-level lows often move even more slowly than expected. March is the most common month for river floods across the southeast U.S., and heavy spring rains are a hallmark of El Niño in this region.

In records going back to 1876, Little Rock, AR, has never seen a March with more than 10.43” of rain (set in 1897). If the ingredients come together as models suggest, Little Rock could approach that record before the month is half over

Figure 2. Rainfall projected for the 7-day period ending at 7:00 am EST Friday, March 11, 2016. Image credit: NOAA/NWS Weather Prediction Center
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1. Shreveport LA gets 13 inches of rain in 24 hours

A Flash Flood Emergency has been declared in Northwest Louisiana, including the city of Shreveport, where over a foot of rain fell in just 24 hours, from Tuesday morning through Wednesday morning. At Shreveports's Barksdale Air Force Base, 13.16" had fallen as of 10 am EST Wednesday, and over 14 inches of rain fell just to the southeast of Shreveport near Bossier City. The heavy rains have led to numerous high water rescues and flooded homes and streets. Near Shreveport, up to 80 homes were flooded and a nursing home had to be evacuated due to rising waters, according to the Associated Press, and evacuations have been ordered in Greenwood, Haughton, Homer, Minden and Rayville, Louisiana. The flooding problems extend into Eastern Texas, where multiple bridges have been washed out northeast of Marlin, Texas. Although the heaviest rains moved out of Eastern Texas and Northern Louisiana late Wednesday morning, near-record levels of atmospheric moisture for this time of year--more than 200% of average--remain in place over the region, and renewed rounds of heavy rain are likely through Friday. Extreme flooding rains were spreading into Southern Arkansas on Wednesday morning, and rainfall amounts of a foot in 24 hours are possible there, as well. Additional major flash flooding over the next few days is also possible in Houston, San Antonio, Austin, Shreveport, Little Rock, Memphis and New Orleans.

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