Mesoscale Discussion 907

Issued

Jun 10, 2021, 1:47 PM MDT (19:47 UTC)

Expired

Jun 10, 2021, 3:15 PM MDT

In force

88 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

Counties Blaine County, MT, Fergus County, MT, Golden Valley County, MT, Musselshell County, MT, Petroleum County, MT, Phillips County, MT, Stillwater County, MT, Sweet Grass County, MT, Valley County, MT, Wheatland County, MT

The Billings radar (KBLX), 163 km from the middle of the area, began a volume at 19:46 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 252Jun 10, 2:50 PM MDT

623 
ACUS11 KWNS 101947
SWOMCD
SPC MCD 101947 
MTZ000-102115-

Mesoscale Discussion 0907
NWS Storm Prediction Center Norman OK
0247 PM CDT Thu Jun 10 2021

Areas affected...west-central/northeast Montana

Concerning...Severe potential...Watch possible 

Valid 101947Z - 102115Z

Probability of Watch Issuance...60 percent

SUMMARY...A few severe storms may develop early this afternoon to
the northwest of a deepening surface low across southwestern
Montana. Isolated supercells capable of severe wind gusts, large
hail, and perhaps tornadoes will track northward toward the Canadian
border into this evening.

DISCUSSION...Afternoon water vapor imagery showed a well-defined
upper-trough and jet streak approaching the northern Rockies. As
deep-layer ascent and stronger southwesterly flow aloft have begun
to overspread western and central Montana, new updrafts have been
observed along the crests of the higher terrain. Easterly low-level
advection north of the surface low was noted transporting higher
theta-e air with 40s and 50s F dewpoints as far west as LWT. As
ascent from the approaching trough continues to increase, steepening
mid-level lapse rates and the warming/moistening airmass should
result in weak to moderate destabilization by mid afternoon.
Deep-layer shear is strong, with 60-70 kts of 0-6km shear noted from
the 12z Glasgow and Great Falls RAOBs. Sufficient buoyancy and
plentiful shear will act to organize any updrafts into supercells or
short line segments as they track north-northeastward this
afternoon/evening. The primary severe risk appears to be the
potential for large hail and damaging wind gusts given strong
background flow and steep mid-level lapse rates. Hodographs are
long, but weak in the lowest several kilometers. A tornado or two
cannot be ruled out given the potential for rotating storms and
locally backed northeasterly flow near the stationary front north of
the low. Convective trends will be monitored for a possible watch
issuance in the next 1 to 2 hours.

..Lyons/Guyer.. 06/10/2021

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

ATTN...WFO...BYZ...GGW...TFX...

LAT...LON   45660993 46271046 47041025 47840976 48710902 49000845
            49040624 48940612 48200654 47640710 46840780 46010847
            45590914 45660993

Mesoscale Discussions in Montana, 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.