12AM Day 2 Convective Outlook for Monday, October 20. NO SEVERE THUNDERSTORM AREAS FORECAST
SUMMARY
Severe storms are unlikely Monday.
Synopsis
A strong negative tilt mid-level trough is forecast to move over the Northeast early Monday as a second upper trough deepens over the Great Lakes. Strong ascent from these features will support surface cyclogenesis over the Saint Lawrence Valley and the upper Midwest. This will result in increased south/southwesterly low-level flow ahead of a surface cold front sweeping across southern New England. A second cold front will also move southeast across the Plains and Midwest with strong high pressure behind it. Showers and some low-topped thunderstorms are possible early Monday along the surging cold front across coastal New England. Otherwise, isolated thunderstorms are possible across the Great Lakes and over south Florida, but severe storm potential is limited.
Southern New England
Strong forcing from the upper trough and fast-moving cold front will help force a shallow convective band along the front late Sunday into early Monday across the Mid Atlantic and southern New England. With little to no diurnal heating and only shallow moisture expected, any destabilization ahead of this convective band should be minimal (SBCAPE less than 300 J/kg). Most model guidance shows very thin cape profiles rooted just above the surface with poor low-level lapse rates over southern NY into MA/CT and RI. While some lightning and a sporadic strong wind gusts cannot be ruled out with an locally stronger line segments, especially near the coast Monday morning; uncertainty on storm organization and sufficient surface-based destabilization suggests a severe risk is currently unlikely. Low-topped storms will remain possible beneath the upper trough over New England through the afternoon as the surface low occludes, but with an increasingly narrow surface-based warm sector and very weak instability.