Alert archive / North Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1437
The Storm Prediction Center issued this mesoscale discussion at Aug 7, 2021, 7:12 PM CDT for 5 counties in North Dakota; Brown County, Day County, Marshall County, South Dakota. It was in force for 93 min.
The area
The outline as issued.
The facts
- Issued
- Aug 7, 2021, 7:12 PM CDT (00:12 UTC)
- Expired
- Aug 7, 2021, 8:45 PM CDT
- In force
- 93 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Dickey County, ND, LaMoure County, ND, Logan County, ND, Ransom County, ND, Sargent County, ND, Brown County, SD, Day County, SD, Marshall County, SD
The radar
The Aberdeen radar (KABR), 76 km from the middle of the area, began a volume at 00:13 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
Aberdeen, SD (KABR), launched 00:00Z, 0.2 hours before the alert went out and 137 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
- 2053 J/kg
- Mixed-layer CIN
- -13 J/kg
- Mixed-layer LCL
- 1417 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 86 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 4.0
The text
As transmitted.
959
ACUS11 KWNS 080012
SWOMCD
SPC MCD 080012
SDZ000-NDZ000-080145-
Mesoscale Discussion 1437
NWS Storm Prediction Center Norman OK
0712 PM CDT Sat Aug 07 2021
Areas affected...Portions of the Dakotas
Concerning...Severe potential...Watch unlikely
Valid 080012Z - 080145Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated severe storms near an area of low pressure across
the Dakotas may pose a risk for damaging winds and isolated hail
this evening. A non-supercell tornado may also be possible in
vicinity of the surface low. Storm coverage is expected to remain
low suggesting a watch is unlikely.
DISCUSSION...Evening water vapor imagery showed a well defined
shortwave trough moving out of the Rockies and into the central
Plains. Ahead of this wave, an area of low pressure at the surface
was observed near the north Dakota south Dakota Border. Lift from a
cold front extending south from the low has resulted in isolated
storm development along an arcing line from south-central North
Dakota to near Aberdeen, South Dakota. Despite prominent smoke and
haze, daytime heating and dewpoints in the upper 60s F have resulted
in moderate instability (2000-3000 J/kg of MLCAPE). Winds aloft
however are weak, with the Aberdeen VAD indicating effective shear
remains below 30 kts. Severe potential appears modest, but a few
stronger multicell storms may become organized early this evening.
Steep mid-level lapse rates and large buoyancy will support the
potential for severe hail and damaging outflow winds with the
strongest storms. Enhanced stretching from 0-3km CAPE in excess of
100 J/kg east of the low center and locally greater vertical
vorticity beneath the vortmax may also support a non-supercell
tornado this evening. Uncertainty on storm organization remains
high, suggesting that a weather watch is unlikely.
..Lyons/Hart.. 08/08/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FGF...ABR...BIS...
LAT...LON 46839944 46909911 46889850 46729801 46469758 45999710
45489718 45139766 45069844 45289872 45599876 45989900
46189955 46639977 46839944Nearby
Mesoscale Discussions in North Dakota, 2021Mesoscale Discussions in South Dakota, 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.