Between April 28 – May 1, 2017, a series of severe weather events affected the Central United States, producing life-threatening flooding and a major tornado outbreak. It formed out of a disturbance in the Southwestern United States on April 28, and caused significant impacts, including a heavy snowstorm in the Rockies, and other types of severe weather. Up to of snow fell on the cold side of the system, and up to a foot of rain fell in and around the central parts of the nation.

Numerous tornadoes ripped through the central United States as a powerful storm system developed in the Rockies. Mainly EF0 and EF1 tornadoes were seen on April 28. Tornadoes made multiple appearances in Louisiana, Texas, and Arkansas on this day. Massive swaths of large hail up to two inches (5.1 cm) in diameter and wind speeds up to 81 mph (135 km/h) were also reported on April 28. On April 29, two long-lived and particularly dangerous tornadoes ripped through the Canton, Texas area, killing four people and injuring many others. One tornado was rated EF3 and the other was rated EF4 on the Enhanced Fujita Scale. April 30 saw a total of 41 tornadoes touch down in Arkansas, Missouri, Louisiana, Mississippi, Tennessee, and Alabama. An EF2 tornado killed one person and caused considerable damage in the town of Durant, Mississippi.

Tornadoes were not the only threat with this storm complex as a large number of Flash Flood Watches went up in areas the storms were impacting. Isolated rainfall totals up to eleven inches were seen in far south Indiana and parts of Missouri. The heavy rainfall combined with the strong winds from the severe thunderstorms allowed for trees to be brought down easily in locations that received excessive rainfall. Streets were reported to be impassable and some roads were even closed due to the heavy rains. A few generally weak tornadoes were scattered around on May 1. Tornadoes were not the primary threat on May 1; however straight line winds in excess of 85 mph (137 km/h) were reported throughout the eastern seaboard of the United States. Overall, this outbreak produced 77 tornadoes and 20 deaths. Only five of the deaths were a direct result of tornadoes, while other deaths occurred from the flooding and heavy snow the storm system brought as well.

Meteorological synopsis April 28–29

On April 26, 2017, the Storm Prediction Center (SPC) outlined a 30% risk for severe weather over northeastern Texas, southeastern Oklahoma, southwestern Arkansas, and northwestern Louisiana, encompassed by a larger 15% risk area. A shortwave trough was expected to amplify over the southern Rocky Mountains and move eastwards through the southern Great Plains, accompanied by a strong cold front. Severe thunderstorms were expected to develop along the boundary, moving eastwards through Texas and into the lower Mississippi Valley, where the atmosphere would be "moderately to strongly unstable". The following day, April 27, at 07:22 UTC, the SPC outlined an enhanced (3 out of 5) categorical risk, or 30% probabilistic risk, over the previous area of the 15% and 30% risks.

On April 28, at 17:41 UTC, the SPC extended their enhanced risk to stretch into southern Missouri, now accompanied by a smaller 45% probabilistic risk for severe weather in Texas, Oklahoma, Arkansas, and Louisiana. Severe thunderstorms were expected to form and pose threats of large hail, damaging winds, and tornadoes. Weather vapor imagery denoted an amplifying mid-level trough situated over the western United States, as a ridge built over the Southeast coast. A mid-level low would develop and move eastwards from the Four Corners into the Texas Panhandle and western Oklahoma. In the lower levels, a surface low initially situated over the southern Plains would slowly move northeast into the Ozarks, while a stationary frontal zone sat east-northeast from central Oklahoma through Missouri and into the Ohio Valley. An arctic cold front moved southwards into the Permian Basin, and a Pacific cold front combined and accelerated southeastwards across Texas and into the lower Sabine Valley by Sunday, April 30. Strong low-level southerly flow would advect a maritime tropical airmass, consisting of lowest 100-mb mean mixing ratios (at or above 16 g/kg) and translating to 70-74 degree F surface dewpoints, into much of the warm sector across Arkansas, Louisiana, Texas, and northeastwards into northern portions of the lower Mississippi Valley.  Ongoing thunderstorms were likely across portions of Oklahoma near the terminus of a 60-kt low level jet as the cold front encroached on the warm sector. Isolated severe hail and severe gusts were possible with the initial activity. An elevated mixed layer and capping inversion allowed a very unstable boundary layer (MLCAPE 2500-4000 J/kg) to develop to the south of convective outflow and cloud debris across southeast Oklahoma & Arkansas and into east-central Texas.  Weather models indicated storm development moving southwestwards into north-central Texas during the afternoon of April 29 in association with a couple of storm clusters. The more substantial severe risk was to be timed with the ejection of a strong mid-level vorticity maximum moving eastwards into the southern Plains during the late afternoon and through the overnight. More uncertain was the potential development of quasi-discrete storms developing ahead of the front. Any supercells that managed to develop and sustain themselves in the moisture-rich environment with a sizable hodograph were probable to pose a tornadic threat. As the mid-level wave turned into the region, strengthening effective shear profiles from 30-kt to 45-60 kt produced favorable conditions for a mature squall line moving eastward across this region and moving into Arkansas and Louisiana. The threat for severe gusts and associated wind damage were expected to become more widespread in Arkansas, Louisiana, and Texas after nightfall.

On April 29, at the 06:00 UTC outlook, the SPC continued their enhanced risk, alongside a 5% risk for tornadoes, lasting through the 1300, 1630, and 2000 UTC outlooks. Strong winds associated with the aforementioned upper low would translate across west Texas and the southern Plains that night, alongside by 150–180 m height falls at 500 mb. At lower levels in advance of the upper low, a broad low-level jet was placed over parts of Texas, Oklahoma, Louisiana, and Arkansas, with 50-60 kt winds in the 1–2 km agl level. This would provide strong low-level shear on April 29, with strengthening deep-layer shear progressing eastward across the southern plains towards the lower Mississippi Valley that night. A ridge of high pressure centered over the Atlantic Ocean, allowing high levels of atmospheric pressure originating from the Gulf of Mexico to focus along the front. This caused thunderstorm training (clusters of heavy rain and thunderstorms slowly progressing eastwards).  For the next six hours, the front remained mostly indifferent as it moved slightly eastwards, although a squall line was beginning to form, increasing the threat for large hail, damaging wind gusts and a few tornadoes. Although the overall setup that day was not favorable for a widespread tornado outbreak, thunderstorms from earlier in the day left behind an outflow boundary across northeastern Texas, resulting in a localized area of enhanced low-level helicity. Deep moisture, high levels of CAPE, and low LCL heights were also present in the area as multiple thunderstorms rode the boundary and dramatically intensified into large tornadic supercells, going on to produce the East Texas tornadoes.

April 30–May 1 Overnight into the early hours of April 30, the activity pushed eastward and a powerful squall line of severe thunderstorms with numerous embedded tornadic circulations swept through the Mississippi Valley. Throughout the day, the low tracked northeast into the Plains and intensified, causing some snowfall in the mountainous regions and in colder places, meanwhile severe weather continued to occur in the South. Forty-two tornadoes occurred across the Southern United States that afternoon and evening, with much of the activity centered in Mississippi. While many of these tornadoes were weak, some were large and wedge-shaped and reached EF2 intensity. One of these strong tornadoes killed one person and caused damage in the town of Durant, Mississippi. On May 1, another squall line of severe storms developed further to the north. The Storm Prediction Center ended up issuing a tornado watch for parts of Pennsylvania and New York. The storms ended up producing multiple embedded weak tornadoes across the region. Tornadoes were not the primary threat; however, and straight line wind gusts up to were reported in parts of Pennsylvania and New York which caused a significant amount of damage in the impacted areas. Numerous reports of downed trees and power lines were received throughout parts of the Northeastern United States before the event came to an end.

Confirmed tornadoes

Canton/Eastern Texas tornadoes

On April 29, multiple tornadoes, some large, destructive, and deadly, moved through the East Texas counties of Henderson, Van Zandt, Rains, and Hopkins. Over the course of 3 hours and 15 minutes, the tornadoes killed four people, injured over 49, and wrought severe damage across the area. The strongest of the tornadoes were given mid-range EF4, low-end EF3, and mid-range EF2 ratings respectively by the National Weather Service (NWS) in Fort Worth/Dallas, Texas. The strongest, a large, violent EF4 rain wrapped tornado first began in Henderson County. The tornado tracked north/northeastwards, reaching EF2 strength southeast of Eustace before weakening as it entered Van Zandt County. The tornado intensified back to EF2 strength shortly after, damaging or destroying multiple structures as it moved north-northeastwards towards the Canton area. Passing between Phalba and Tundra, the tornado rapidly intensified to EF4 strength, destroying a well-built two story brick home. Weakening to EF3 strength, the tornado began to turn towards the northwest, striking the community of Jackson. The tornado damaged or destroyed numerous structures southwest of Canton before rapidly weakening and dissipating near High, leaving two people dead and 25 more injured.