Upscale Supercell Growth Fuels 75-90 MPH Wind Threat in MT-Dakotas — SevereWX

Supercells raging over southeastern Montana are beginning to merge and grow upscale, setting the stage for intense damaging winds across northwest South Dakota and western North Dakota.

The Storm Prediction Center's latest Mesoscale Discussion (1018) highlights this evolution within ongoing PDS Severe Thunderstorm Watch 285. Storms in southern Custer County, MT, show multiple strong updrafts and lengthening motion vectors on radar, pointing to consolidation into an organized cluster or bowing segment.

Key Threats:

• Winds: 75-90 mph gusts likely in the next 30-90 minutes, driven by steep T/TD spreads (highs near 40°F) fueling robust downdrafts.
• Hail: 1.50-2.50 inches.
• Tornadoes: Up to 90 mph intensity possible.

A highly unstable environment—MLCAPE over 2500 J/kg and 45-55 kt deep-layer shear—supports violent thunderstorms merging near a frontal boundary. Enhanced convergence will spawn new updrafts amid the chaos, amplifying the wind potential.

This comes amid active severe weather in the northern Plains on June 7, 2026, with CAM models backing the rapid upscale shift.

Stay prepared: Monitor local NWS updates, secure outdoor items, avoid flooded roads, and shelter in interior rooms if storms approach. Have a NOAA radio and severe weather plan ready.