SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0158 PM CST Mon Dec 14 2020

Valid 142000Z - 151200Z


The strong/gusty wind threat associated with thunderstorms has
decreased across eastern North Carolina. Minimal thunderstorm
potential is evident across the rest of the contiguous United States
through tonight.

...20Z Update...
A surface cold front is in the process of clearing the NC Coast, and
any isolated strong/gusty wind threat associated with convection is
quickly moving offshore. Therefore, low severe wind probabilities
have been removed from eastern NC with this update. Thunderstorms
are not expected across the remainder of the CONUS through the end
of the period owing to dry and/or stable conditions.

..Gleason.. 12/14/2020

.PREV DISCUSSION... /ISSUED 1008 AM CST Mon Dec 14 2020/

...Eastern NC...

Late this morning a cold front extends from a weak surface low over
the northern Coastal Plain of NC, through central GA, the central FL
Panhandle and into the eastern Gulf. Quasi-stationary front extends
from the surface low through northeastern NC and into southeast VA.
The low will track northeast and offshore by early afternoon, while
the cold front continues east and off the Atlantic Coast by mid
afternoon. Warm sector dewpoints across eastern NC have risen to the
low to mid 60s F, but instability remains limited due to widespread
clouds and showers with MUCAPE from 200-400 J/kg for parcels lifted
from near 850 mb. The ongoing area of showers with a few embedded
thunderstorms developing along the warm conveyor belt will continue
east during the day. Some potential will exist for this shallow
convection to become surface based as it encounters a warmer and
more unstable boundary layer across eastern NC, though instability
will remain very marginal. Given very strong vertical wind profiles
with 60 kt as low as 0.5 km AGL, some of this higher momentum air
could be transported to the surface within the higher reflectively
rain bands as the surface layer destabilizes farther east. However,
tendency is for the accompanying shortwave trough to deamplify with
only weak cyclogenesis inland which, combined with the very marginal
thermodynamic environment, should limit overall severe threat.

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