A slow-moving, strong upper level storm system moved from the Central Rockies into the Central Plains on the 18th and 19th. A dry line sharpened ahead of this system across western Oklahoma by early afternoon on the 18th, as a frontal boundary over northern Oklahoma shifted north into Kansas as a warm front. Warm, very moist, and very unstable air was in place east of the dry line and south of the warm front, and thunderstorms erupted across western Oklahoma during the early afternoon near the dry line. These storms evolved into a line by the time they moved into and across northwestern Arkansas during the late evening hours. The storms produced a tornado, damaging wind, and hail up to quarter size as they moved across northwestern Arkansas.
A couple additional rounds of thunderstorms on the 19th through the early morning hours of the 20th resulted in isolated flooding to develop across portions of northwest Arkansas.

Thunderstorm Wind in BENTON, ARKANSAS
From 18-MAY-17 22:45:00 to 18-MAY-17 22:45:00 (CST-6)
Location: SILOAM SPGS
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Strong thunderstorm wind gusts snapped large tree limbs.

Thunderstorm Wind in SEBASTIAN, ARKANSAS
From 18-MAY-17 23:05:00 to 18-MAY-17 23:05:00 (CST-6)
Location: GREENWOOD
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm wind gusts were measured to 63 mph.

Thunderstorm Wind in BENTON, ARKANSAS
From 18-MAY-17 23:14:00 to 18-MAY-17 23:14:00 (CST-6)
Location: BENTONVILLE MUNI ARP
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Strong thunderstorm wind snapped large tree limbs near the Bentonville Municipal Airport.

Thunderstorm Wind in BENTON, ARKANSAS
From 18-MAY-17 23:15:00 to 18-MAY-17 23:15:00 (CST-6)
Location: BENTONVILLE MUNI ARP
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

The AWOS at the Bentonville Municipal Airport measured 61 mph thunderstorm wind gusts.

Thunderstorm Wind in BENTON, ARKANSAS
From 18-MAY-17 23:15:00 to 18-MAY-17 23:15:00 (CST-6)
Location: ROGERS
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Strong thunderstorm wind uprooted a tree that fell onto a home.

Thunderstorm Wind in WASHINGTON, ARKANSAS
From 18-MAY-17 23:15:00 to 18-MAY-17 23:15:00 (CST-6)
Location: SPRINGDALE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Strong thunderstorm wind snapped a tree near Mill Street in Springdale.

Thunderstorm Wind in WASHINGTON, ARKANSAS
From 18-MAY-17 23:20:00 to 18-MAY-17 23:20:00 (CST-6)
Location: SPRINGDALE
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Strong thunderstorm wind blew shingles off the roof of a home.

Thunderstorm Wind in FRANKLIN, ARKANSAS
From 18-MAY-17 23:30:00 to 18-MAY-17 23:30:00 (CST-6)
Location: CECIL
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Strong thunderstorm wind blew down trees.

Thunderstorm Wind in FRANKLIN, ARKANSAS
From 18-MAY-17 23:30:00 to 18-MAY-17 23:30:00 (CST-6)
Location: OZARK
Magnitude: 65.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Strong thunderstorm wind blew down trees and power lines.

Thunderstorm Wind in FRANKLIN, ARKANSAS
From 18-MAY-17 23:40:00 to 18-MAY-17 23:40:00 (CST-6)
Location: OZARK
Magnitude: 61.00 EG
Property damage: 4.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Strong thunderstorm wind blew over a trailer and damaged vehicles due to flying debris.

Thunderstorm Wind in FRANKLIN, ARKANSAS
From 18-MAY-17 23:45:00 to 18-MAY-17 23:45:00 (CST-6)
Location: WEBB CITY
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Strong thunderstorm wind blew down trees in Webb City.

Flash Flood in SEBASTIAN, ARKANSAS
From 20-MAY-17 05:00:00 to 20-MAY-17 07:15:00 (CST-6)
Location: BEVERLY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Several roads were flooded in and around Lavaca.

Flood in SEBASTIAN, ARKANSAS
From 20-MAY-17 07:15:00 to 21-MAY-17 07:45:00 (CST-6)
Location: LAVACA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Portions of Highway 252 were closed due to flooding.

Hail in SEBASTIAN, ARKANSAS
From 18-MAY-17 23:11:00 to 18-MAY-17 23:11:00 (CST-6)
Location: FT SMITH
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Tornado in BENTON, ARKANSAS
From 18-MAY-17 23:07:00 to 18-MAY-17 23:09:00 (CST-6)
Location: CENTERTON
Tornado F-scale: EF0
Property damage: 40.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado damaged the roofs of a number of homes, uprooted trees, snapped numerous large tree limbs, and blew down several power poles. Based on this damage, maximum estimated wind in the tornado was 80 to 85 mph.