2AM Day 3 Convective Outlook for Tuesday, October 21. NO SEVERE THUNDERSTORM AREAS FORECAST
SUMMARY
Isolated thunderstorms are possible over the Great Lakes South Florida, and Gulf Coast regions Tuesday. Severe thunderstorms are not expected.
Synopsis and Discussion
The upper low over the East Coast will weaken as it phases with a second upper trough moving across the Great Lakes and Northeast. A cold front will stretch from the surface low over the Great Lakes to the central Gulf Coast and move southeastward through the day. Cool mid-level temperatures beneath the broad low will support very weak buoyancy and some shallow storms across the Great Lakes/Upper OH valley Tuesday afternoon.
Southwest of the primary upper low, subsidence behind a strong northwesterly mid-level jet will strengthen post-frontal high pressure over the central US. Offshore flow associated with the high pressure is expected to scour surface moisture over much of the eastern CONUS outside of south FL and the central Gulf Coast. Isolated storms are possible along typical sea breeze boundaries, though with only weak ascent and little to no vertical shear. Thus, severe storms are unlikely over the CONUS Tuesday.