Mesoscale Discussion 887

Issued

Jun 8, 2021, 2:39 PM MDT (20:39 UTC)

Expired

Jun 8, 2021, 5:15 PM MDT

In force

3 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

80%

Counties Custer County, MT, Dawson County, MT, Garfield County, MT, McCone County, MT, Prairie County, MT, Richland County, MT, Roosevelt County, MT, Rosebud County, MT, Sheridan County, MT, Treasure County, MT, Wibaux County, MT, Divide County, ND, Golden Valley County, ND, McKenzie County, ND, Williams County, ND

The Glasgow radar (KGGW), 115 km from the middle of the area, began a volume at 20:40 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.

• Severe Thunderstorm Watch 247Jun 8, 3:55 PM MDT
• Severe Thunderstorm Watch 248Jun 8, 5:15 PM MDT

882 
ACUS11 KWNS 082040
SWOMCD
SPC MCD 082039 
NDZ000-MTZ000-082315-

Mesoscale Discussion 0887
NWS Storm Prediction Center Norman OK
0339 PM CDT Tue Jun 08 2021

Areas affected...Eastern Montana...western North Dakota

Concerning...Severe potential...Watch likely 

Valid 082039Z - 082315Z

Probability of Watch Issuance...80 percent

SUMMARY...Significant hail and significant wind gusts will be
possible as storms develop and intensify across eastern Montana and
western North Dakota later this afternoon into the evening. A
conditional threat for a couple tornadoes also exists. A WW is
likely to be considered by 6 PM MDT.

DISCUSSION...Mid-level ascent is evident on water-vapor imagery
across parts of western Wyoming into southern Montana. Ahead of the
shortwave trough, strong southeasterly winds continue to advect low
to mid 60s F dewpoints into the western Dakotas and eventually into
eastern Montana. Convective inhibition in eastern Montana is
continuing to decrease given the deepening of cumulus near the North
Dakota border. There is some uncertainty in the timing of storm
initiation, but development along the higher terrain in
south-central Montana is likely to occur earlier given proximity to
the shortwave. Further development is also possible along the warm
front in northeast Montana to near the North Dakota border. Steep
mid-level lapse rates observed on the 19Z GGW sounding with 45-55
kts of effective shear will promote organized storms capable of
large to very large (2+ inches hail), at least initially.
Temperature/dewpoint spreads and overall number of storms will
likely lead to rather quick transition to clusters/bowing segments
capable of severe wind gusts (some of which will exceed 65 kts).

Low-level wind profiles near the warm front into northwest North
Dakota are expected to remain favorable for tornadoes this
afternoon, with even an increase in hodograph size this evening as
850 mb wind strengthen. LCLs will not be particularly low, but areas
near the warm front have seen greater cloud cover most of the day
which will allow for relatively lower dewpoint depressions. The
other question will be storm mode. A couple of tornadoes will be
possible should a storm remain discrete near the boundary.

A WW is likely to be considered by 6 PM MDT.

..Wendt/Guyer.. 06/08/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BIS...BYZ...GGW...

LAT...LON   47830769 48360659 49010489 48990343 48140286 47270338
            46440388 46520418 46160591 46050628 46220758 46670819
            47370816 47830769

Mesoscale Discussions in Montana, 2021Mesoscale Discussions in North Dakota, 2021Every mesoscale discussion in 2021

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.