Arctic Front Slides Southward; Heavy Rainfall Potential Across the South and for Hawaii

An arctic front will slowly drift southward this weekend. This will focus snow, locally heavy, from the Intermountain West, Rockies, Plains, and Great Lakes and eventually into the Northeast. Dangerously cold wind chills behind this arctic front are forecast for most of the Plains this weekend. Moisture will increase across the Gulf Coast and the State of Hawaii where flooding concerns increase. Read More >

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Overview

An active weather system over the Great Basin brought conditions conducive for severe weather over northern and eastern portions of Wyoming on Monday, June 12^th. Heat, moisture and wind shear was greatest in these areas. Storms initially formed near Casper, WY around 12:30pm, moving NNW into southern Johnson County. These storms gradually turned into supercells by 3:00 – 4:00pm, with other convection starting to form in the Big Horn Basin. The first tornadic storm developed around 5:00pm over SW Johnson County, near Barnum. 1” to 1.75” hail was reported near Barnum by 5:15pm, increasing to 2.5” by 5:30pm 5 miles SW of Kaycee. This storm then proceeded to produce multiple vortices, as it neared Kaycee and Mayoworth. Reports of tornadoes came in between 5:35 and 5:50pm, as the storm slowly moved to the NNE.

Tornado
Photos & Video
Radar

Tornadoes:

Tornado - LOCATION
Johnson County, Wyoming
Approximately 2.5 miles SW of Kaycee

Date	Monday, June 12, 2017
Time (Local)	5:30-5:36 pm MDT
EF Rating	EF2
Est. Peak Winds	110-120
Path Length	1.71 miles
Max Width	250 yards
Injuries/Deaths	0
Summary: A tornado touched on a hillside just south of the Middle Fork of the Powder River approximately 2.5 miles southwest of Kaycee, Wyoming. The tornado crossed an open field and then strengthened as it approached Barnum Road (State Highway 190). It was here the tornado completely destroyed an abandoned trailer home, separating the undercarriage from the main structure. The undercarriage was thrown over 200 yards from its origination point. There was some ground scouring observed near this location. After crossing Barnum Road, the tornado traveled north just missing a farm house before traversing the top of Pine Ridge. Extensive tree damage was observed on Pine Ridge and to numerous large cottonwoods between the river and Barnum Road. At its widest, the tornado produced damage approximately 250 yards across along its 1.71 mile path. Additional damage to cottonwood trees was observed east of the path, most likely due to outflow winds associated with the supercell storm.

Track Map

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Photos & Video:


Kaycee Tornado (Source: Mark_Malli)	Kaycee Tornado (Source: Mark_Malli)	Damage Photo (Source: NWS Riverton)	Damage Photo (Source: NWS Riverton)

Radar:


530 PM Reflectivity	530 PM Storm Relative Velocity	532 PM Reflectivity	532 PM Storm Relative Velocity

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Arctic Front Slides Southward; Heavy Rainfall Potential Across the South and for Hawaii

* Updated Wednesday * Johnson County EF2 Tornado - Monday, June 12, 2017 near Kaycee