Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 606
The Storm Prediction Center issued this mesoscale discussion at May 13, 2021, 4:48 PM CDT for Cheyenne County, Decatur County, Rawlins County, Kansas; 4 counties in Nebraska. It was in force for 117 min.
The area
The outline as issued.
The facts
- Issued
- May 13, 2021, 4:48 PM CDT (21:48 UTC)
- Expired
- May 13, 2021, 6:45 PM CDT
- In force
- 117 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Cheyenne County, KS, Decatur County, KS, Rawlins County, KS, Dundy County, NE, Hayes County, NE, Hitchcock County, NE, Red Willow County, NE
The nearest sounding before it
N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 9.8 hours before the alert went out and 132 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 957 m above ground
- 0-6 km bulk shear
- 54 kt
- 0-1 km storm-relative helicity
- 306 m²/s²
- 0-3 km storm-relative helicity
- 262 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
555
ACUS11 KWNS 132149
SWOMCD
SPC MCD 132148
KSZ000-NEZ000-COZ000-132345-
Mesoscale Discussion 0606
NWS Storm Prediction Center Norman OK
0448 PM CDT Thu May 13 2021
Areas affected...southwest NE...far northwest KS
Concerning...Severe potential...Watch unlikely
Valid 132148Z - 132345Z
Probability of Watch Issuance...20 percent
SUMMARY...An isolated risk for large hail and localized severe gusts
may accompany the stronger storms that manage to develop late this
afternoon into the evening. Storm coverage and severe-producing
storms will likely remain too isolated to warrant a severe
thunderstorm watch issuance.
DISCUSSION...Visible satellite imagery late this afternoon shows a
cluster of strong to severe storms over the western part of the NE
Sandhills and another discrete storm near the NE/CO/KS border.
Ample heating has occurred downstream/southeast of the ongoing
activity (as of 2140 UTC) with mid 70s deg F temperatures. Forecast
soundings show rather cool mid-level temperatures (-17 deg C at 500
mb), which is resulting in 500-750 J/kg MLCAPE despite relatively
marginal boundary layer moisture (mid-upper 40s deg F dewpoints).
As a mid-level shortwave trough over the northern High Plains/Black
Hills vicinity continues to approach the region this evening,
support for additional storms developing or maintaining their vigor
into the early evening hours seems plausible. The strong veering
flow with height increasing to 80 kt at 250 mb will aid in storm
venting and possibly hail production considering the long, straight
hodographs and cool mid-level temperatures. Given the current
forecast expectation for limited storm development south of the NE
Sandhills thunderstorm cluster, a severe thunderstorm watch will
likely not be needed farther south over northwest KS and adjacent
parts of NE this evening.
..Smith/Grams.. 05/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GID...LBF...GLD...
LAT...LON 40330216 40610135 40499997 39509995 39350084 39600189
40330216SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 13, 6:08 PM CDT | Mesoscale Discussion | SPC | Cheyenne, Rawlins, Sherman | 2 hr |
| May 13, 2:38 PM CDT | Mesoscale Discussion | SPC | Arthur, Banner, Box Butte, Brown, Cherry, Dawes and 8 more | 3 hr |
Nearby
Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Kansas, 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.