Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 1397
The Storm Prediction Center issued this mesoscale discussion at Jul 30, 2021, 6:31 PM CDT for 17 counties in Nebraska. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Jul 30, 2021, 6:31 PM CDT (23:31 UTC)
- Expired
- Jul 30, 2021, 8:00 PM CDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 404
Counties Blaine County, NE, Brown County, NE, Cherry County, NE, Custer County, NE, Garfield County, NE, Greeley County, NE, Hall County, NE, Hooker County, NE, Howard County, NE, Logan County, NE, Loup County, NE, McPherson County, NE, Rock County, NE, Sherman County, NE, Thomas County, NE, Valley County, NE, Wheeler County, NE
The radar
The North Platte radar (KLNX), 38 km from the middle of the area, began a volume at 23:35 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
N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 11.5 hours before the alert went out and 108 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.
- Mixed-layer CAPE
- 1419 J/kg
- Mixed-layer CIN
- -169 J/kg
- Mixed-layer LCL
- 1255 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 154 m²/s²
- 0-3 km storm-relative helicity
- 120 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.8
The text
As transmitted.
060 ACUS11 KWNS 302331 SWOMCD SPC MCD 302331 NEZ000-310100- Mesoscale Discussion 1397 NWS Storm Prediction Center Norman OK 0631 PM CDT Fri Jul 30 2021 Areas affected...Nebraska Concerning...Tornado Watch 404... Valid 302331Z - 310100Z The severe weather threat for Tornado Watch 404 continues. SUMMARY...Severe threat continues across ww404. DISCUSSION...Upper high has settled south into northeast OK early this evening. As a result, a fair amount of convection has developed around the western periphery of this feature across the higher terrain of CO into southeast WY. Over the last few hours, mid-level flow has gradually turned more northwesterly across NE and this is providing substantial directional turning with height along/just north of the surface boundary that remains draped across the southern third of the state. Strong surface heating is noted across western/southern NE which is contributing to MLCAPE values near 4000 J/kg along a corridor from near BBW-FNB. Several slow-moving supercells have evolved between BBW-TIF with subsequent movement southeast at only 10-15kt. Over the last half hour or so, new thunderstorms are developing near the front over Garden County. With time, both of these clusters should gradually spread/propagate southeast along/just north of the wind shift. ..Darrow.. 07/30/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GID...LBF... LAT...LON 42920133 42319834 40729834 41330132 42920133
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 30, 3:24 PM CDT | Mesoscale Discussion | SPC | Adams, Arthur, Blaine, Boone, Buffalo, Clay and 22 more | 2 hr |
| Jul 30, 4:04 PM CDT | Tornado Watch | SPC | Blaine, Brown, Buffalo, Cherry, Custer, Dawson and 15 more | 6 hr |
Nearby
Mesoscale Discussions in Nebraska, 2021Every 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.