Alert archive / Minnesota / Mesoscale Discussions in 2018

Mesoscale Discussion 1485

September 20, 2018Allamakee County, Iowa; 30 counties in Minnesota; 28 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Sep 20, 2018, 5:29 PM CDT for Allamakee County, Iowa; 30 counties in Minnesota; 28 counties in Wisconsin. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Sep 20, 2018, 5:29 PM CDT (22:29 UTC)
Expired
Sep 20, 2018, 7:30 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
All 59 counties

Allamakee County, IA, Blue Earth County, MN, Brown County, MN, Carver County, MN, Cottonwood County, MN, Dakota County, MN, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Goodhue County, MN, Hennepin County, MN, Houston County, MN, Le Sueur County, MN, Martin County, MN, McLeod County, MN, Mower County, MN, Nicollet County, MN, Olmsted County, MN, Ramsey County, MN, Redwood County, MN, Renville County, MN, Rice County, MN, Scott County, MN, Sibley County, MN, Steele County, MN, Wabasha County, MN, Waseca County, MN, Washington County, MN, Watonwan County, MN, Winona County, MN, Adams County, WI, Barron County, WI, Buffalo County, WI, Chippewa County, WI, Clark County, WI, Columbia County, WI, Crawford County, WI, Dunn County, WI, Eau Claire County, WI, Jackson County, WI, Juneau County, WI, La Crosse County, WI, Marathon County, WI, Marquette County, WI, Monroe County, WI, Pepin County, WI, Pierce County, WI, Portage County, WI, Richland County, WI, Rusk County, WI, Saint Croix County, WI, Sauk County, WI, Taylor County, WI, Trempealeau County, WI, Vernon County, WI, Waupaca County, WI, Waushara County, WI, Wood County, WI

The radar

The La Crosse radar (KARX), 100 km from the middle of the area, began a volume at 22:31 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 10.5 hours before the alert went out and 130 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 2018-09-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 18 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Minneapolis, MN at 12:00Z on 2018-09-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 195 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
18 J/kg
Mixed-layer CIN
-80 J/kg
Mixed-layer LCL
461 m above ground
0-6 km bulk shear
48 kt
0-1 km storm-relative helicity
195 m²/s²
0-3 km storm-relative helicity
20 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.1

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 20, 2:15 PM CDTMesoscale DiscussionSPCBuena Vista, Cerro Gordo, Cherokee, Clay, Dickinson, Emmet and 12 more3 hr
Sep 20, 2:31 PM CDTMesoscale DiscussionSPCAdair, Adams, Audubon, Boone, Buena Vista, Calhoun and 23 more119 min
Sep 20, 3:11 PM CDTSevere Thunderstorm WatchSPCAdair, Adams, Audubon, Boone, Buena Vista, Calhoun and 38 more8 hr
Sep 20, 5:48 PM CDTMesoscale DiscussionSPCAudubon, Boone, Bremer, Buena Vista, Butler, Calhoun and 37 more57 min
Sep 20, 6:23 PM CDTTornado WatchSPCAllamakee, Chickasaw, Floyd, Howard, Mitchell, Winneshiek5 hr
Sep 20, 3:33 PM CDTTornado WatchSPCBlue Earth, Brown, Carver, Cottonwood, Dakota, Faribault and 22 more4 hr

Nearby

Mesoscale Discussions in Minnesota, 2018Mesoscale Discussions in Wisconsin, 2018Mesoscale Discussions in Iowa, 2018Every mesoscale discussion in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.