Alert archive / North Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1327
The Storm Prediction Center issued this mesoscale discussion at Jul 22, 2021, 2:24 PM MDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 22, 2021, 2:24 PM MDT (20:24 UTC)
- Expired
- Jul 22, 2021, 4:30 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Carter County, MT, Fallon County, MT, Wibaux County, MT, Billings County, ND, Bowman County, ND, Dunn County, ND, Golden Valley County, ND, McKenzie County, ND, Slope County, ND, Stark County, ND, Butte County, SD, Harding County, SD, Lawrence County, SD, Crook County, WY
The radar
The Bismarck radar (KBIS), 248 km from the middle of the area, began a volume at 20:27 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
Bismarck Municip, ND (KBIS), launched 12:00Z, 8.4 hours before the alert went out and 252 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
- 104 J/kg
- Mixed-layer CIN
- -415 J/kg
- Mixed-layer LCL
- 1354 m above ground
- 0-6 km bulk shear
- 10 kt
- 0-1 km storm-relative helicity
- 38 m²/s²
- 0-3 km storm-relative helicity
- 10 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
894 ACUS11 KWNS 222024 SWOMCD SPC MCD 222024 NDZ000-SDZ000-MTZ000-WYZ000-222230- Mesoscale Discussion 1327 NWS Storm Prediction Center Norman OK 0324 PM CDT Thu Jul 22 2021 Areas affected...Parts of eastern Montana...northeastern Wyoming and the western Dakotas Concerning...Severe potential...Watch unlikely Valid 222024Z - 222230Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorms overspreading the region through 6 PM MDT may not become particularly organized, but could still continue to produce a few strong to locally severe surface gusts. DISCUSSION...Thunderstorm activity has become increasingly widespread within lee surface troughing across the higher plains, as well as across the Black Hills vicinity, within/above a hot and deeply-mixed boundary-layer that appears characterized by CAPE on the order of 500-1000 J/kg. This appears to be aided by forcing for ascent associated with a weak impulse progressing through the mean mid/upper ridging, which likely will be maintained across the region into this evening. Within this regime westerly deep-layer mean flow and shear appear on the order of a generally modest 20-30 kt, which, coupled with the weak CAPE, seem likely to limit the potential for substantive organization. Still, storms have already produced a few observed strong surface gusts ranging from 39-47 kt, and this could continue, with perhaps an isolated severe gust or two, as activity develops eastward through 23-00Z. ..Kerr/Hart.. 07/22/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...UNR...BYZ...GGW... LAT...LON 48140406 48210207 44080332 44150512 46250525 48140406
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 22, 1:50 PM MDT | Mesoscale Discussion | SPC | Broadwater, Fergus, Garfield, Golden Valley, Judith Basin, Meagher and 5 more | 2 hr |
| Jul 22, 4:07 PM MDT | Severe Thunderstorm Watch | SPC | Daniels, Fergus, Garfield, Golden Valley, McCone, Musselshell and 6 more | 5 hr |
| Jul 22, 4:42 PM MDT | Mesoscale Discussion | SPC | Adams, Grant, Hettinger, Sioux | 3 hr |
Nearby
Mesoscale Discussions in North Dakota, 2021Mesoscale Discussions in Montana, 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.