Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS02 KWNS 071705
SPC AC 071704
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1104 AM CST Wed Dec 07 2016
Valid 081200Z - 091200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
Severe thunderstorms are not forecast across the contiguous United
States for Thursday and Thursday night.
A longwave trough will continue to shift eastward over the eastern
U.S. during the period. A low-amplitude ridge is forecast over the
western states ahead of an approaching northeast Pacific trough. In
the low levels, an expansive Arctic
anticyclone will encompass the area to the east of the Rockies.
Frontolysis will continue into the start of the day-2 period across
the FL straits. To the north of the surface boundary, weak forcing
for ascent coupled with heating during the day may yield a few
thunderstorms over Everglades and Keys vicinity. Weak lapse rates
and a weak wind profile will preclude the development of strong
...lower Great Lakes...
An Arctic airmass overspreading the lower Great Lakes with surface
water temperatures in the 45-50 F range will support mesoscale
snowbands, most organized over the long axis of Lakes Erie and
Ontario as the lower troposphere moistens/cools during the day
Thursday. High lake-induced equilibrium levels...over 5-km for much
of the day...and relatively warm boundary-layer temperatures will
support a sufficient depth of the -10 to -30 F layer to support
thunder in the stronger bands to the lee of both lakes, particularly
over the Tug Hill Plateau to the east of Lake Ontario.