Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 1330
The Storm Prediction Center issued this mesoscale discussion at Jul 22, 2021, 8:04 PM MDT for Daniels County, Roosevelt County, Sheridan County, Montana; Burke County, Divide County, Williams County, North Dakota. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Jul 22, 2021, 8:04 PM MDT (02:04 UTC)
- Expired
- Jul 22, 2021, 10:00 PM MDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 386
Counties Daniels County, MT, Roosevelt County, MT, Sheridan County, MT, Burke County, ND, Divide County, ND, Williams County, ND
The radar
The Glasgow radar (KGGW), 135 km from the middle of the area, began a volume at 02:04 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
Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 2.1 hours before the alert went out and 133 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
- 1077 J/kg
- Mixed-layer CIN
- -95 J/kg
- Mixed-layer LCL
- 2422 m above ground
- 0-6 km bulk shear
- 55 kt
- 0-1 km storm-relative helicity
- -33 m²/s²
- 0-3 km storm-relative helicity
- 117 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -1.1
The text
As transmitted.
086
ACUS11 KWNS 230205
SWOMCD
SPC MCD 230204
NDZ000-MTZ000-230400-
Mesoscale Discussion 1330
NWS Storm Prediction Center Norman OK
0904 PM CDT Thu Jul 22 2021
Areas affected...northeast Montana into northwest North Dakota
Concerning...Severe Thunderstorm Watch 386...
Valid 230204Z - 230400Z
The severe weather threat for Severe Thunderstorm Watch 386
continues.
SUMMARY...A few severe gusts remain possible across eastern parts of
WW 386, and storms may affect extreme northwestern North Dakota.
However, additional watches are unlikely.
DISCUSSION...A cluster of storms with a history of measured severe
gusts continues to rapidly progress across northeast MT, and will
likely affect a small portion of ND. While temperatures are cooler
downstream of these storms, greater boundary-layer moisture content
yields higher MLCAPE values per objective analysis, and effective
shear remains favorable at 40+ kt.
Given only a small threat area in time and space east of WW 386,
another watch is unlikely. Isolated wind damage remains the primary
concern, but hail cannot be ruled out if storms can utilize the
better moisture prior to capping increasing too much.
..Jewell.. 07/23/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BIS...GGW...
LAT...LON 48120272 47660572 47640629 47880643 48330615 49030609
49000227 48120272SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 23, 12:25 PM MDT | Mesoscale Discussion | SPC | Traill | 2 hr |
| Jul 23, 4:04 PM MDT | Mesoscale Discussion | SPC | Barnes, Cass, Dickey, Emmons, Grant, LaMoure and 6 more | 3 hr |
Nearby
Mesoscale Discussions in Montana, 2021Mesoscale Discussions in North 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.