Alert archive / North Dakota / Mesoscale Discussions in 2023
Mesoscale Discussion 1621
The Storm Prediction Center issued this mesoscale discussion at Jul 18, 2023, 5:42 PM CDT for 22 counties in North Dakota; 19 counties in South Dakota. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 18, 2023, 5:42 PM CDT (22:42 UTC)
- Expired
- Jul 18, 2023, 7:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 41 counties
Barnes County, ND, Benson County, ND, Burleigh County, ND, Dickey County, ND, Eddy County, ND, Emmons County, ND, Foster County, ND, Griggs County, ND, Kidder County, ND, LaMoure County, ND, Logan County, ND, McIntosh County, ND, Nelson County, ND, Pierce County, ND, Ramsey County, ND, Ransom County, ND, Sargent County, ND, Sheridan County, ND, Sioux County, ND, Steele County, ND, Stutsman County, ND, Wells County, ND, Beadle County, SD, Brown County, SD, Buffalo County, SD, Campbell County, SD, Dewey County, SD, Edmunds County, SD, Faulk County, SD, Hand County, SD, Hughes County, SD, Hyde County, SD, Jerauld County, SD, Lyman County, SD, Marshall County, SD, McPherson County, SD, Potter County, SD, Spink County, SD, Stanley County, SD, Sully County, SD, Walworth County, SD
The radar
The Aberdeen radar (KABR), 109 km from the middle of the area, began a volume at 22:44 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
Bismarck Municip, ND (KBIS), launched 12:00Z, 10.7 hours before the alert went out and 120 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
- 1281 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km storm-relative helicity
- 141 m²/s²
- 0-3 km storm-relative helicity
- 207 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
227
ACUS11 KWNS 182242
SWOMCD
SPC MCD 182242
NDZ000-SDZ000-190045-
Mesoscale Discussion 1621
NWS Storm Prediction Center Norman OK
0542 PM CDT Tue Jul 18 2023
Areas affected...portions of central/eastern ND/SD
Concerning...Severe potential...Watch possible
Valid 182242Z - 190045Z
Probability of Watch Issuance...60 percent
SUMMARY...Isolated to widely scattered strong to severe
thunderstorms are expected by 00z. Large hail will be the main
hazard with this activity. A watch may be needed in the next couple
of hours.
DISCUSSION...Southerly low-level flow ahead of a sharpening and
southeastward-advancing cold front has allowed for a corridor of
mid/upper 60s F dewpoints to overspread much of central ND/SD.
Dewpoints decrease to the upper 50s/low 60s over the eastern
Dakotas. Pockets of strong heating and steep midlevel lapse rates
have allowed for moderate to strong destabilization. Warm advection
is resulting in some cloudiness on the eastern periphery of stronger
instability, and some elevated weak convection is currently ongoing.
However, further west closer to the cold front and zone of stronger
low-level convergence, deepening cumulus has been noted in visible
satellite. As stronger ascent spreads eastward this evening,
isolated to widely scattered thunderstorm development is expected.
Low-level flow will remain rather weak, but effective shear
magnitudes greater than 40 kt will support organized cells.
Elongated hodographs, in conjunction with steep midlevel lapse rates
and 30-40 kt westerly flow between 3-6 km suggest large (and
possibly isolated very large/2+ inch diameter) hail will be possible
with this activity. Timing of convective development is a little
uncertain, but the severe risk is expected to increase by 00z, and a
severe thunderstorm watch may be needed in the next couple of hours.
..Leitman/Edwards.. 07/18/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FGF...FSD...ABR...BIS...UNR...
LAT...LON 44580116 46370112 47460101 48070080 48419999 48509910
48329851 47979790 47379761 46629753 45769754 44259824
43859897 43819958 43810013 43960067 44580116SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 18, 6:20 PM CDT | Severe Thunderstorm Watch | SPC | Barnes, Benson, Cass, Dickey, Eddy, Emmons and 15 more | 8 hr |
| Jul 17, 8:38 PM CDT | Mesoscale Discussion | SPC | Bennett, Custer, Fall River, Jackson, Lawrence, Meade and 4 more | 2 hr |
| Jul 17, 11:42 PM CDT | Mesoscale Discussion | SPC | Bennett | 2 hr |
| Jul 18, 1:15 PM CDT | Mesoscale Discussion | SPC | Custer, Lawrence, Pennington | 3 hr |
Nearby
Mesoscale Discussions in North Dakota, 2023Mesoscale Discussions in South Dakota, 2023Every mesoscale discussion in 2023
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.