Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS02 KWNS 070639
SPC AC 070637
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1237 AM CST Wed Dec 07 2016
Valid 081200Z - 091200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The greatest potential for thunderstorms Thursday into Thursday
night should be across South Florida, and a strike or two cannot be
ruled out in the lee of the Great Lakes attendant to lake effect
snow. Severe storms are not expected across the contiguous United
A longwave trough will shift eastward into the eastern half of the
U.S. Thursday through Thursday night. Meanwhile, a low-amplitude
ridge is expected to advance inland across the western states, as a
northeast Pacific trough approaches Washington and Oregon. Several
midlevel impulses attendant to the Pacific trough are expected to
move through Washington and Oregon into the northern Rockies and
adjacent southwest Canada. At the surface, a large Arctic
anticyclone will continue building over the Great Plains, and should
expand east across much of the eastern U.S. from the Ohio Valley and
central Appalachians southward through the Atlantic seaboard and the
Gulf of Mexico.
The cold front on the leading extent of the Arctic anticyclone will
spread south through the Florida Peninsula. Residual moisture and
surface heating in vicinity of a stalled boundary across South
Florida should result in afternoon MUCAPE of 500-1000 J/kg. Despite
weak forcing aloft, a few thunderstorms will be possible as the
Arctic cold front advances south Thursday afternoon and evening.
...Lee of the Great Lakes...
Cold lower-tropospheric air spreading across the relatively warm
lake temperatures will support steep 0-3-km lapse rates. This will
result in sufficient instability for lightning production over and
in lee of the Great Lakes. The lightning will be associated with
lake effect snow, while guidance suggests thunderstorm coverage
should remain less than 10 percent, precluding the inclusion of a
categorical general-thunderstorm area.