Heavy Rain and Flash Flooding in the West; Heat Expands in the Central U.S.

Monsoonal moisture will produce showers and thunderstorms with heavy rain over parts of the Southwest, Great Basin, and Central Rockies through Monday. Flash flooding is possible, especially in and around burn scars and in areas of steep terrain. Heat will persist across the Central U.S. early this week, spreading into the Ohio Valley and Mid-Atlantic later this week. Read More >

Overview

On March 06, 2017, an early spring severe weather outbreak produced large hail and damaging wind in Wisconsin, and even three tornadoes across Minnesota. This marks the earliest date in Minnesota history that a tornado was ever recorded. The previous record was March 18, 1968. The loop to the right shows a comparison of visible and infrared satellite imagery from the GOES16 satellite, along with radar reflectivity, lightning, and warnings at 5:00 PM March 06, 2017. The line of thunderstorms was located across Central Minnesota and extends southward into Iowa.

Figure 1: Damage from Freeborn County in the town of Clarks Gove, Minnesota.


Figure 2: Damage from Sherburne County near Elk Lake, Minnesota.	Figure 3: Damage from Faribault County by Rice Lake, Minnesota.

Tornado
Radar
Storm Reports
Environment

Tornadoes:

Tornado - Zimmerman Area EF-1
Sherburne County MN

Date	06 March, 2017
Time (Local)	5:39 - 5:55 PM
EF Rating	EF-1
Est. Peak Winds	100 - 110 MPH
Path Length	8.9 Miles
Max Width	300 Yards
Injuries/Deaths	None
Summary: An EF-1 tornado touched down about 5 miles west of Zimmerman and traveled northeast 8.9 miles, dissipating before reaching Highway 169. The storm also produced non-tornadic scattered tree damage due to strong inflow into the storm in a few locations, including on the east side of Highway 169, just south of Princeton.

Track Map

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Tornado - Clark's Grove Area EF-1
Freeborn County MN

Date	06 March, 2017
Time (Local)	5:38 - 5:51 PM
EF Rating	EF-1
Est. Peak Winds	100 - 110 MPH
Path Length	12.3 Miles
Max Width	300 Yards
Injuries/Deaths	None
Summary: An EF-1 tornado started in Freeborn County, MN and traveled 12.3 miles through the towns of Clarks Grove and Geneva before lifting in southern Steele County. Peak winds were estimated at 100 to 110 mph which caused damage to homes, buildings, and trees.

Track Map

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Tornado - Bricelyn Area EF-1
Faribault County MN

Date	06 March, 2017
Time (Local)	5:04 - 5:15 PM
EF Rating	EF-1
Est. Peak Winds	90 MPH
Path Length	9.6 Miles
Max Width	200 Yards
Injuries/Deaths	None
Summary: An EF-1 tornado developed just northwest of Bricelyn in Faribault County, MN and traveled 9.6 miles before lifting west of the Freeborn County line. Peak winds were estimated at 90 mph. The tornado destroyed a garage, barn and a few sheds. Power poles were snapped. Windows were blown in and roof damage also occurred. The most concentrated area of damage was at Pihl's Campground on Rice Lake, six miles south of Wells.

Track Map

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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

Radar:

Header


Base Radar Reflectivity loop from 4:30 PM to 8:00 PM as the storms moved across Minnesota into Wisconsin.	Base Reflectivity (top) and Storm Relative Velocity (bottom) show the storm northwest of Zimmerman MN. The circulation is indicated by the white arrows	Base Reflectivity (top) and Storm Relative Velocity (bottom) show the storm near Clarks Grove MN. The circulation is indicated by the white arrows

Storm Reports

The image to the right shows severe weather that was reported on Monday March 06, 2017. Several hundred reports of severe weather were observed across the central United States. Minnesota and Wisconsin had mostly damaging wind along with some large hail. See the full list of storm reports here.

There was building damage and uprooted trees near Clarks Grove MN in Freeborn county in southern Minnesota. Meanwhile in Sherburne county there were large trees and power lines down. Most of this damage occurred between 5:00 PM and 7:00 PM on Monday, March 06, 2017.

Satellite and Radar comparison with Warnings

Environment

A powerful jet caused a surface low to develop over the eastern Dakotas. Warm moist air ahead of this surface low led to instability, and the
wind shear profile was favorable for severe thunderstorms.


Figure 1: 300 mb wind speed (fill), heights (contours), and winds - A strong upper level jet in a negatively tilted trough led to cyclogenesis across the Midwest. The strong winds created a wind shear profile favorable for severe thunderstorms. Data generated using the GFS 06.18 analysis.	Figure 2: 850 mb temperatures (fill), heights (contours), and winds - Very warm air was in place across the Upper Mississippi River Valley ahead of the surface low. Data generated using the GFS 06.18 analysis.	Figure 3: Surface pressure (fill and contours) and winds - A very deep surface low of 982 mb was located across the eastern Dakotas at 12:00 PM March 06, 2017. Data generated using the GFS 06.18 analysis.

Storms developed quickly in the late afternoon and persisted through the evening.


Radar reflectivity at 3:00 PM.	Radar reflectivity at 4:00 PM.	Radar reflectivity at 5:00 PM.

A narrow tongue of instability developed in the warm sector ahead of the cold front with MLCAPE values over 1000 J/kg by late afternoon.


Mixed layer CAPE (red contours) and CIN (blue shading) with surface winds at 3:00 PM.	Mixed layer CAPE (red contours) and CIN (blue shading) with surface winds at 4:00 PM.	Mixed layer CAPE (red contours) and CIN (blue shading) with surface winds at 5:00 PM.

Strong low level shear supported rotation in the storms that developed along the cold front.


0 to 1 km shear (blue contours and wind barbs) at 3:00 PM.	0 to 1 km shear (blue contours and wind barbs) at 4:00 PM.	0 to 1 km shear (blue contours and wind barbs) at 5:00 PM.

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Heavy Rain and Flash Flooding in the West; Heat Expands in the Central U.S.

Summary of March 06 2017 Severe Weather Outbreak - Earliest Known Tornado in Minnesota's History