A ridge of high pressure ("H") flattened enough during the first week of October, 2019 to allow the flow aloft to bring storm systems ("L") and cold fronts into Arkansas.
In the picture: A ridge of high pressure ("H") flattened enough during the first week of October, 2019 to allow the flow aloft to bring storm systems ("L") and cold fronts into Arkansas.
 

A ridge of high pressure that persisted over Arkansas in September with dry/hot conditions finally broke down in early October. The pattern started changing, with cold fronts heading this way and bringing chances of rain and cooler air.

 

Forecast maps showed a cold front pushing into Arkansas from the Plains on 10/06/2019. Scattered to numerous showers and thunderstorms accompanied the front, followed by cooler air.
Forecast Map at 700 pm CDT (10/05)  |  Forecast Map at 700 am CDT (10/06)
Forecast Map at 700 pm CDT (10/06)  |  Forecast Map at 700 am CDT (10/07)
Loop
In the pictures: Forecast maps showed a cold front pushing into Arkansas from the Plains on 10/06/2019. Scattered to numerous showers and thunderstorms accompanied the front, followed by cooler air.
 

One such front was on the doorstep to the northwest to begin the 6th. Ahead of the front, showers and thunderstorms were ongoing in northwest sections of the state. By daybreak, some locations in the far northwest (Benton County) had three to four inches of precipitation. By 700 pm CDT, twenty four hour rainfall was over six inches at Highfill and Rogers (both in Benton County). In fact, radar estimates were over ten inches in spots. Flash flooding was serious in the northwest, with numerous roads closed in Benton and Washington Counties. This included sections of Highways 12, 59, 264, and 412. High water flowed into homes, and several people were rescued from stalled vehicles.

 

There was a moderate to severe drought (D1/D2) in far southern Arkansas on 10/08/2019.
Drought Conditions (Percent Area)
Category Coverage
None 68.88%
D0-D4 31.12%
D1-D4 10.97%
D2-D4 1.36%
D3-D4 0%
D4 0%
In the picture: There was a moderate to severe drought (D1/D2) in far southern Arkansas on 10/08/2019.
 

Heading into mid-October, there were drought conditions over southern Arkansas. At El Dorado (Union County), only 0.41 inch of rain settled the dust from July 22nd through the end of September. The situation improved somewhat from October 1st through the 13th, with 1.31 inches of precipitation. This was only the beginning.

A cold front that pushed through the region from the Plains on the 10th stalled along the Gulf Coast and moved back to the north. Late on the 14th into the 15th, precipitation focused along the front, and was most intense toward the Louisiana border. Several inches of rain was measured where drought conditions existed.

 

Forty eight hour rainfall at 700 am CDT on 10/16/2019.
In the picture: Forty eight hour rainfall at 700 am CDT on 10/16/2019.
 

Forty eight hour amounts through 700 am CDT on the 16th included 4.95 inches at El Dorado (Union County), 4.67 inches at Moro Bay State Park (Bradley County), 4.17 inches at Felsenthal Lock and Dam (Ashley/Union Counties), 3.56 inches at Fordyce (Dallas County), 3.29 inches at Portland (Ashley County), 2.73 inches at Eudora (Chicot County), 1.84 inches at Monticello (Drew County), and 1.77 inches at Texarkana (Miller County).

For the month (through the 15th), it was very wet in the northwest. Rainfall was three to more than four inches above average at Fayetteville (Washington County) and Harrison (Boone County). Due to this event, it was a similar story in parts of the south, including El Dorado (Union County).

 

Precipitation in October, 2019 (Through the 15th)
Site Amount Normal +/- % of Normal
Fayetteville (NW AR) 6.51 2.13 +4.38 306%
Harrison (NC AR) 5.51 1.64 +3.87 336%
Jonesboro (NE AR) 2.20 2.00 +0.20 110%
Fort Smith (WC AR) 3.65 2.00 +1.65 182%
Little Rock (C AR) 1.61 2.18 -0.57 74%
West Memphis (EC AR) 3.92 1.98 +1.94 198%
Texarkana (SW AR) 2.70 2.21 +0.49 122%
El Dorado (SC AR) 6.26 2.38 +3.88 263%
Pine Bluff (SE AR) 1.37 2.26 -0.89 61%

 

There was a slight to enhanced risk of severe weather across much of Arkansas late on 10/20/2019 and early the next morning. The forecast is courtesy of the Storm Prediction Center.
In the picture: There was a slight to enhanced risk of severe weather across much of Arkansas late on 10/20/2019 and early the next morning. The forecast is courtesy of the Storm Prediction Center.
 

Up to this point, there was plenty of rain to talk about, but severe weather was limited. That changed late on the 20th/early on the 21st. Hit and miss thunderstorms popped up quickly in central and eastern Oklahoma. Storms eventually gelled into a line that rapidly crossed Arkansas.

 

Link of Interest
Help with Severe Weather Categories

 

Supercells (storms with rotating updrafts) were likely across northern and western Arkansas in the twelve hour period ending at 700 am CDT on 10/21/2019. The graphics are courtesy of the College of DuPage.
Supercell Composite at 700 pm CDT (10/20)  |  Supercell Composite at 1000 pm CDT (10/20)
Supercell Composite at 100 am CDT (10/21)  |  Supercell Composite at 400 am CDT (10/21)
Supercell Composite at 700 am CDT (10/21)  |  Loop
In the pictures: Supercells (storms with rotating updrafts) were likely across northern and western Arkansas in the twelve hour period ending at 700 am CDT on 10/21/2019. The graphics are courtesy of the College of DuPage.
 

Winds turned with height, and this created rotation in several storms. Given this, there was a possibility of isolated tornadoes. Along lines of storms, such tornadoes are often brief and weak.

 

Severe weather reports in the twenty four hour period ending at 700 am CDT on 10/21/2019.
In the picture: Severe weather reports in the twenty four hour period ending at 700 am CDT on 10/21/2019.
 

As the line of storms tore through the region, a roof was removed from a building in Subiaco (Logan County). A carport was blown over at Conway (Faulkner County), with the same happening to a shed near Paragould (Greene County). Trees and/or powerlines were downed between Ashdown and Foreman (both in Little River County), northwest of Benton (Saline County), southeast of Bradley (Lafayette County), at Bergman (Boone County), Bismarck (Hot Spring County), Coal Hill (Johnson County), Danville (Yell County), De Queen (Sevier County), Hollis (Perry County), Little Rock (Pulaski County), Monette (Craighead County), Nashville (Howard County), and Pine Bluff (Jefferson County). Winds gusted to 58 mph at Carlisle (Lonoke County), 55 mph at Newport (Jackson County), and 53 mph at Flippin (Marion County) and Harrison (Boone County).

Tragically, a downed tree fell through a house about five miles east of Rogers (Benton County) toward Beaver Lake. A 66-year-old man inside the home was killed. A damage survey conducted by the National Weather Service in Tulsa, OK indicated that winds gusted as high as 80 to 90 mph at times.

 

A supercell (storm with rotating updrafts and exhibiting features such as a hook echo and strong rotation) was near Highfill (Benton County) at 1218 am CDT on 10/21/2019. The supercell was part of a line of storms moving through western Arkansas.
Reflectivity at 1218 am CDT (10/21)  |  Storm Relative Velocity at 1218 am CDT (10/21)
More About Rotation
In the pictures: A supercell (storm with rotating updrafts and exhibiting features such as a hook echo and strong rotation) was near Highfill (Benton County) at 1218 am CDT on 10/21/2019. The supercell was part of a line of storms moving through western Arkansas. 
 

Just after midnight CDT, two tornadoes (rated EF1/EF2) were confirmed from Siloam Springs to Rogers (both in Benton County). The stronger of these was on the ground for just over 31 miles! Hangers were damaged at an airport close to Siloam Springs (Benton County). Numerous homes and businesses were hit, and outbuildings were destroyed.

 

Record Width in Arkansas?

The long track tornado in Benton County was not only noted for its miles on the ground, it had a width of 1.5 miles! A preliminary peek at past data (since 1950) shows only one track that was wider. The Vilonia (Faulkner County) tornado of April 25, 2011 had a width of 2900 yards or roughly 1.65 miles.

 

In the picture: A weak tornado (rated EF1) damaged several structures in Tyronza (Poinsett County) early on 10/21/2019.
 

Between 400 am and 430 am CDT on the 21st, a weak tornado (rated EF1) traveled through rural areas (5.4 mile track) from ten miles southeast of Bradley (Lafayette County) to five miles southeast of Taylor (Columbia County). The tornado uprooted or snapped trees and partially removed roofs from a couple of homes. Just before 600 am CDT, a short-lived (1.2 mile track) weak tornado (rated EF1) caused some structural damage to an elementary school in Tyronza (Poinsett County). A gas station convenience store collapsed. A semi truck was also knocked on its side. At least five people were injured. About a half hour later, one other weak tornado (rated EF0) was identified east of Wilson (Mississippi County) near the Mississippi River.