Alert archive / Nebraska / Mesoscale Discussions in 2015

Mesoscale Discussion 1772

September 7, 20154 states

The Storm Prediction Center issued this mesoscale discussion at Sep 7, 2015, 2:18 PM CDT for 4 states. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Sep 7, 2015, 2:18 PM CDT (19:18 UTC)
Expired: Sep 7, 2015, 3:45 PM CDT
In force: 87 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 26 counties

Fremont County, IA, Mills County, IA, Page County, IA, Brown County, KS, Cloud County, KS, Jewell County, KS, Marshall County, KS, Mitchell County, KS, Nemaha County, KS, Republic County, KS, Washington County, KS, Atchison County, MO, Holt County, MO, Cass County, NE, Fillmore County, NE, Gage County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Nuckolls County, NE, Otoe County, NE, Pawnee County, NE, Richardson County, NE, Saline County, NE, Thayer County, NE

The radar

The Topeka radar (KTWX), 133 km from the middle of the area, began a volume at 19:20 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.

Severe Thunderstorm Watch 505Sep 7, 3:40 PM CDT

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 7.3 hours before the alert went out and 143 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 347 J/kg
Mixed-layer CIN: -137 J/kg
Mixed-layer LCL: 646 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 2 m²/s²
0-3 km storm-relative helicity: -38 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 6, 8:42 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Black Hawk, Boone, Bremer and 44 more	93 min
Sep 6, 11:41 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Allamakee, Audubon, Benton, Black Hawk and 38 more	64 min
Sep 7, 3:37 PM CDT	Severe Thunderstorm Watch	SPC	Anderson, Brown, Clay, Cloud, Coffey, Dickinson and 17 more	6 hr
Sep 7, 5:46 PM CDT	Mesoscale Discussion	SPC	Cheyenne	119 min
Sep 7, 6:23 PM CDT	Mesoscale Discussion	SPC	Chase, Clay, Cloud, Dickinson, Ellsworth, Geary and 18 more	97 min
Sep 7, 6:38 PM CDT	Severe Thunderstorm Watch	SPC	Allen, Butler, Chase, Greenwood, Marion, Woodson	3 hr
Sep 7, 6:50 PM CDT	Severe Thunderstorm Watch	SPC	Cheyenne, Decatur, Graham, Norton, Rawlins, Sheridan and 2 more	2 hr

Nearby

Mesoscale Discussions in Nebraska, 2015 Mesoscale Discussions in Kansas, 2015 Mesoscale Discussions in Iowa, 2015 Every mesoscale discussion in 2015

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.