SPC 0700Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1120 PM CST Sat Dec 12 2020

Valid 141200Z - 151200Z


The risk for severe thunderstorms appears negligible across the
U.S., Monday through Monday night.

A belt of westerlies emanating from the mid-latitude Pacific will
remain a prominent influence across much of the U.S. through this
period, with one embedded short wave trough expected to be
progressing into/across the southern Appalachians vicinity by 12Z
Monday.  Models indicate a continued rapid east-northeastward
acceleration across the southern Mid Atlantic coast by late Monday
afternoon, accompanied by a still modest, but deepening, surface

This is forecast to occur as a more vigorous short wave trough, on
the leading edge of northwesterly flow emanating from the
northwestern Canadian Arctic latitudes, accelerates eastward within
strengthening cyclonic flow across the upper Great Lakes into the
Canadian Maritimes.  There may be increased phasing of the two
perturbations east of the north Atlantic Seaboard, accompanied by
substantive further deepening of the surface cyclone to the
southeast of the Canadian Maritimes.

In the wake of these features, and in advance of another significant
amplifying mid-level trough digging across the southern Rockies and
central/southern Great Plains, a confluent mid-level regime is
forecast to support building cold surface ridging across and east of
the Mississippi Valley into the Atlantic Seaboard.  This will tend
to suppress surface cyclogenesis to the lee of the southern Rockies,
with generally stable conditions being maintained across most areas
east of the Rockies, in addition to much of the West.

...Southern Mid Atlantic...
Thermodynamic profiles characterized by a stable boundary-layer and
generally weak mid-level lapse rates are expected to prevail along
the warm frontal zone, ahead of the developing cyclone expected to
migrate into the western Carolinas by 12Z Monday.  However, at least
some forecast soundings (perhaps most notably the NAM) suggest that
modest moisture return, in the presence of lift aided by low-level
warm advection, may contribute to profiles at least marginally
conducive to convection capable of producing lightning.  Any such
activity probably will be focused just ahead of strong mid-level
subsidence warming, which is forecast to accompany a strong cyclonic
mid-level jet nosing across the Carolinas by mid afternoon Monday.

Low-level and deep-layer shear may become strong by Monday afternoon
across the Outer Banks area of North Carolina, where weak
boundary-layer destabilization may not be entirely out of the
question.  However, appreciable potential for strong to severe
thunderstorm activity still seems focused offshore, closer to the
Gulf stream, late Monday afternoon and evening.

..Kerr.. 12/13/2020

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