SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0156 PM CST Wed Dec 16 2020

Valid 162000Z - 171200Z


Isolated strong to severe thunderstorms will remain possible across
parts of coastal North Carolina and west-central Florida this

...20Z Update...
An isolated damaging wind and brief tornado threat should continue
for the next couple of hours along/near the NC Coast and Outer
Banks. Strong low-level shear is present to the northeast of a
deepening surface low across this region, which should continue to
prove favorable for updraft rotation. Although instability should
remain fairly weak, strong low-level warm/moist advection should
support surface-based storms where dewpoints can increase into the
low to mid 60s. Severe probabilities have been adjusted to account
for the northeastward movement of a band of convection located near
and north of the surface low. For more information on the short-term
severe risk across eastern NC, see Mesoscale Discussion 1853.

Widespread precipitation has limited the degree of instability
across much of the central FL Peninsula this afternoon. The
potential for an isolated strong to damaging wind gust should remain
confined along/near parts of the west-central FL Gulf Coast through
the remainder of the afternoon as storms move onshore. Upper 60s to
low 70s surface dewpoints are present across this area and slightly
greater destabilization has occurred in the presence of moderate
deep-layer shear.

..Gleason.. 12/16/2020

.PREV DISCUSSION... /ISSUED 1054 AM CST Wed Dec 16 2020/

An intense shortwave trough is tracking across the lower MS and TN
valleys today, with large-scale forcing overspreading much of the
southeast US.  Surface cyclogenesis is currently occurring off the
SC/NC coast.  Latest radar loop shows a line of showers and
thunderstorms developing in vicinity of the surface low/warm front. 
These storms are expected to track northward today and affect the
coastal counties of eastern NC.  Most model solutions keep
surface-based CAPE over the Sound and Outer Banks.  Nevertheless,
strong vertical shear may support supercell structures in this
activity, with a risk of locally damaging wind gusts or a brief
tornado.  This threat should end by 23z as storms move out to sea.

Scattered thunderstorms are occurring this morning over the
northeast Gulf of Mexico, along and ahead of an approaching cold
front.  There is considerable doubt that storms can maintain this
strength as they move ashore into west-central FL this afternoon,
due to the limited moisture/instability over that region.  While a
storm or two may produce gusty winds, the overall severe threat
appears marginal.

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