Alert archive / Nebraska / Mesoscale Discussions in 2021

Mesoscale Discussion 1223

July 9, 202113 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Jul 9, 2021, 10:20 PM CDT for 13 counties in Nebraska. It was in force for 115 min.

The area

The outline as issued.

The facts

Issued: Jul 9, 2021, 10:20 PM CDT (03:20 UTC)
Expired: Jul 10, 2021, 12:15 AM CDT
In force: 115 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 363

Counties Butler County, NE, Clay County, NE, Fillmore County, NE, Gage County, NE, Hamilton County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Otoe County, NE, Polk County, NE, Saline County, NE, Seward County, NE, York County, NE

The radar

The Grand Island radar (KUEX), 105 km from the middle of the area, began a volume at 03:21 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 nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 3.3 hours before the alert went out and 107 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: 2603 J/kg
Mixed-layer CIN: -130 J/kg
Mixed-layer LCL: 1447 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 90 m²/s²
0-3 km storm-relative helicity: 186 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 8.1

Open this sounding in Storm Lab

The text

As transmitted.

621 
ACUS11 KWNS 100320
SWOMCD
SPC MCD 100320 
NEZ000-KSZ000-100515-

Mesoscale Discussion 1223
NWS Storm Prediction Center Norman OK
1020 PM CDT Fri Jul 09 2021

Areas affected...southeast NE

Concerning...Severe Thunderstorm Watch 363...

Valid 100320Z - 100515Z

The severe weather threat for Severe Thunderstorm Watch 363
continues.

SUMMARY...Significant severe gusts are becoming more likely as a
squall line organizes and quickly moves into southeast NE through
midnight.  Widespread severe gusts are probable (60-70 mph) and
localized gusts 75-85 mph are possible in east-southeast oriented
swaths.

DISCUSSION...Radar mosaic shows an intensifying squall line over
east-central NE moving southeast at 40-45 kt.  Surface analysis
shows backed low-level surface winds to the east of the squall line
over eastern NE within a baroclinic zone.  Surface temperatures have
only slowly cooled into the low-mid 80s near I-80 with surface
dewpoints in the mid 70s.  As a result, it seems plausible upwards
of 17-18 g/kg lowest 100 mb mean ratios are present ahead of the
squall line.  As the squall line continues to mature over the next
hour, this moisture-rich airmass will enhance the potential for
large, water-loaded storms.  The early signs of this occurring are
indicated by echo tops exceeding 60 kft in Buffalo County in recent
radar data.  The favorable wind profile (40-50 kt effective shear)
and large buoyancy will strongly favor a severe MCS across southeast
NE during the next 1-3 hours as a terminus of a strengthening LLJ
focuses over the area.  Significant severe gusts (75-85 mph) are
possible in localized swaths within broader severe gusts with the
squall line.

..Smith.. 07/10/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OAX...TOP...GID...

LAT...LON   40569842 41129790 41319733 40869611 40229607 39969676
            40569842

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 9, 8:21 PM CDT	Mesoscale Discussion	SPC	Adams, Antelope, Arthur, Blaine, Boone, Boyd and 44 more	114 min
Jul 9, 8:45 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Antelope, Boone, Buffalo, Cedar, Clay and 28 more	8 hr
Jul 9, 9:06 PM CDT	Severe Thunderstorm Watch	SPC	Arthur, Blaine, Boyd, Brown, Cherry, Custer and 15 more	6 hr
Jul 9, 9:12 PM CDT	Mesoscale Discussion	SPC	Burt, Cass, Cuming, Dodge, Douglas, Gage and 13 more	2 hr
Jul 9, 9:58 PM CDT	Severe Thunderstorm Watch	SPC	Burt, Butler, Cass, Cuming, Dodge, Douglas and 14 more	7 hr
Jul 9, 10:44 PM CDT	Mesoscale Discussion	SPC	Box Butte, Garden, Grant, Sheridan	91 min
Jul 10, 1:37 AM CDT	Mesoscale Discussion	SPC	Custer, Dawson, Lincoln, Logan, Thomas	53 min
Jul 10, 1:45 AM CDT	Mesoscale Discussion	SPC	Custer, Dawson, Lincoln, Logan, Thomas	60 min
Jul 10, 1:20 PM CDT	Mesoscale Discussion	SPC	Butler, Cass, Douglas, Fillmore, Gage, Jefferson and 12 more	115 min
Jul 10, 2:18 PM CDT	Severe Thunderstorm Watch	SPC	Cass, Douglas, Gage, Johnson, Lancaster, Nemaha and 4 more	7 hr
Jul 10, 3:44 PM CDT	Mesoscale Discussion	SPC	Gage, Johnson, Nemaha, Pawnee, Richardson	91 min
Jul 10, 5:27 PM CDT	Mesoscale Discussion	SPC	Richardson	2 hr

Nearby

Mesoscale Discussions in Nebraska, 2021 Every mesoscale discussion in 2021

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.