SPC AC 121620
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1020 AM CST Tue Dec 12 2017
Valid 121630Z - 131200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
Isolated lightning strikes will be possible across parts of coastal
Massachusetts and vicinity this afternoon and early evening.
...Synopsis and Discussion...
Large-scale upper troughing over the eastern CONUS will further
amplify today as several embedded shortwave troughs rotate around
its base. At the surface, a cold front will move eastward off the
Atlantic coast by this evening as a low consolidates near coastal
MA/NH. Preceding the front, low-level warm air advection should
increase across coastal MA this afternoon, and recent NAM/RAP
forecast soundings suggest MUCAPE up to 300 J/kg may be attained as
mid-level lapse rates modestly steepen. Large-scale forcing for
ascent will also strengthen across this region in the same time
frame, and isolated lightning strikes may occur with the more robust
elevated convection. These isolated thunderstorm chances will
quickly diminish this evening as the cold front moves offshore.
Dry/stable conditions will dominate across the rest of the CONUS
today, with negligible thunderstorm potential evident.
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