Quebec Outflow Fuels Supercell Surge into Maine, NH, VT — SevereWX

A mesoscale convective vortex crossing from Quebec is setting the stage for intensifying thunderstorms along a key outflow boundary into western Maine, northern New Hampshire, and Vermont this afternoon.

SPC's Mesoscale Discussion 1613 highlights renewed storm development near the St. Lawrence Valley and international border, where rich low-level moisture (dewpoints near 70°F) meets CAPE over 2000 J/kg. A weakening elevated mixed-layer cap is allowing storms to root deeper into this unstable air, promoting scattered supercells by 4-6 PM EDT.

Strong shear will support rotating updrafts capable of large hail (1.5-2.5 inches), damaging gusts to 80 mph, and a tornado or two (120-145 mph peak intensity) as storms spread southeast.

The setup eyes a 60% chance of a watch issuance through 2015Z. Activity trails west-northwest from Quebec, intensifying near the border before pushing into the forecast area.

Peak Threats:

• Hail: Golf ball to tennis ball size
• Wind: 65-80 mph
• Tornado: EF2 strength possible

Stay alert if you're in western Maine (around Greenville), northern New Hampshire, or Vermont—have a severe weather plan ready, monitor radar, and heed local warnings to stay safe.