Strong Atmospheric River Bringing Heavy Rain to the Pacific Northwest; Areas of Snow in the North-Central and Eastern U.S.

A strong atmospheric river will bring prolonged heavy rainfall along with gusty winds to the Pacific Northwest through much of this week. The heavy rainfall may lead to widespread urban and river flooding. Accumulating snow is expected over parts of the central Appalachians and Mid-Atlantic today as well as the Upper Midwest and the Upper Great Lakes this evening into Tuesday. Read More >

Overview

Several supercell thunderstorms developed during the morning and early afternoon hours of Thursday, July 18, 2019, starting around 11 AM near Moose Lake, MN. The first storm produced half-dollar size hail near Foxboro, WI, before dissipating. Another supercell thunderstorm developed near Chaffey, WI, and tracked east-southeastward to a few miles northwest of Solon Springs, WI. The storm then made a right turn and moved into the town of Gordon, WI, where it produced a tornado. The tornado lifted a few minutes after it formed in Douglas County. The supercell storm gradually weakened as it moved across southern Bayfield County and dissipated near Namekagon around 4 PM.

Tornado
Photos & Video
Radar
Environment

Tornadoes

Tornado - Gordon, WI
Douglas County, WI

Date	July 18, 2019
Time (Local)	2:29 PM to 2:35 PM
EF Rating	EF-1
Est. Peak Winds	100-110 mph
Path Length	1.3 miles
Max Width	160 yard
Injuries/Deaths	0
Summary: The tornado began east of the intersection of Sand Road and Cabin Lane. The NWS Duluth storm survey picked up the damage path where it crossed Cabin Lane several hundred yards west of Sand Road. Numerous uprooted and broken softwood trees were noted on either side of Cabin Lane at that location. The damage at that location was consistent with high-end EF-0 wind speeds of 75 to 85 mph. The tornado continued east-southeast and strengthened to EF-1 intensity south of the intersection of Sand Road and Cabin Lane. Extensive tree damage was noted with nearly all trees in the area broken or uprooted. This damage seemed consistent with winds of 85 to 95 mph. From that location to a point just west of Schaefer Road, a path was cut through the trees which was approximately 80 yards wide and approximately one-half mile in length. All the trees in this area were either broken or uprooted and the damage was consistent with winds of 100 to 110 mph. The tornado weakened quickly after crossing Schaefer Road. A few broken branches and uprooted trees were noted along Jackson Road and locations farther east. It seems the tornado lifted between Schaefer Road and Jackson Road, which is where we approximated the end of the track.

Track Map

Downloadable KMZ File

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

Header


Trees flattened roughly a quarter mile south of the intersection of Cabin Lane and Shaefer Road. Photo taken by NWS Duluth Damage Survey team looking northwest.	Funnel cloud seen north from Lower Eau Claire Lake around 3 PM CDT. (Screen capture from a video courtesy of Al Schmidt and Kirsten Odegard)	Several trees downed and a few uprooted near a homestead on Cabin Lane. Photo taken by NWS Duluth Damage Survey team.

Radar

Radar imagery from KDLH radar in Duluth, MN. The loop starts at 2:02 CDT and ends at 2:54 CDT.

Reflectivity (left) and Storm Relative Velocity (right)

Environment

A 250 hPa jet streak lifted out of the Upper Midwest into Ontario. In addition, a subtle 500 hPa shortwave trough lifted from the Northern Plains into the Upper Midwest on July 18th. These features helped aid in lift aloft for thunderstorm development. A bit lower in the atmosphere, strong southwesterly moisture advection was present per 850 hPa analysis.


Figure 1: 12Z (7 AM CDT) 250 hPa SPC analysis	Figure 2: 12Z (7 AM CDT) 500 hPa SPC analysis	Figure 3: 18Z (1 PM CDT) 850 hPa SPC Mesoanalysis

At the surface the nearest feature is a warm front lifting northward into southern Minnesota. An elevated warm front (not shown) was lifting into a region of high instability. Surface Based CAPE values (an indication of how unstable the atmosphere is) ranged from 2000-2500 J/kg around 1 PM with no Surface Based CIN. 0-6 km Bulk shear values ranged from 50 to 60 knots. The high amount of shear combined with the instability is indicative that supercell thunderstorms are possible provided there is sufficient moisture and lift to get storms going. 0-1 km bulk shear values were in the 10 to 15 knot range, which is right around the low end of the threshold that is indicative of a tornado threat. Lifted Condensation Level Heights were between 750 to 1000 meters and the Significant Tornado Parameter (STP) value was around 1. Typically the majority of significant tornadoes (EF2 or greater) are associated with values greater than 1. The thunderstorm that produced the tornado was able to develop due to the lift provided by an outflow boundary that was left over from a thunderstorm that moved through during the morning hours.


Figure 4: WPC 18Z (1 PM CDT) Surface Analysis	Figure 5: 18Z (1 PM CDT) Surface Based CAPE from SPC Mesoanalysis	Figure 6: 18Z (1 PM CDT) 0-6 km Bulk Shear from SPC Mesoanalysis


Figure 7: 18Z (1 PM CDT) 0-1 km Bulk Shear from SPC Mesoanalysis	Figure 8: 18Z (1 PM CDT) Lifted Condensation Level (LCL) heights from SPC Mesoanalysis	Figure 9: 18Z (1 PM CDT) Significant Tornado Parameter from SPC Mesoanalysis

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Strong Atmospheric River Bringing Heavy Rain to the Pacific Northwest; Areas of Snow in the North-Central and Eastern U.S.

July 18, 2019, Gordon, Wisconsin, Tornado