SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0141 PM CST Mon Feb 22 2021

Valid 222000Z - 231200Z


Isolated strong wind gusts remain possible with a narrow band of
showers/thunderstorms this afternoon across eastern North Carolina
and southeast Virginia.

...Eastern North Carolina through southeast Virginia...

Only minor changes have been made to previous forecast which remains
on track. A forced band of low-topped convection extends from
southeast VA through eastern NC. Some increase in reflectivity along
the leading band has been noted. This convective band is embedded
within deep forcing for ascent and strong wind profiles accompanying
a progressive shortwave trough. Some of this momentum might remain
capable of reaching the surface due to precipitation loading and
modest evaporative cooling within the heavier bands as evidenced by
the 41 kt gust at Wakefield VA. However, overall severe threat will
remain limited due to the very marginal thermodynamic environment.

..Dial.. 02/22/2021

.PREV DISCUSSION... /ISSUED 1021 AM CST Mon Feb 22 2021/

...Eastern NC/southeastern VA this afternoon...
A midlevel trough and associated surface cold front/trough now
crossing the Appalachians will continue eastward to the Mid-Atlantic
and southeast Atlantic coasts late this afternoon into early
tonight.  Strong forcing for ascent along the front (represented by
the current band of precipitation across the Piedmont), and modest
low-level warming/destabilization to its east, will support a band
of low-topped convection this afternoon from southeast VA into
eastern NC.  There should be enough cloud breaks to allow surface
temperatures to warm into the upper 50s across southeastern VA to
lower 60s across eastern NC, as boundary-layer dewpoints increase to
the 50-55 F range within a modifying air mass off the western
Atlantic.  This will result in weak surface-based buoyancy (SBCAPE
of 100-250 J/kg), and convection may become deep enough for charge
separation and isolated lightning flash potential.  Regardless of
the presence of lightning, very strong low-midlevel winds could be
transported to the surface in the shallow convective band.

Otherwise, the cold front will move southeastward into south
GA/north FL later this afternoon and continue southward into central
FL by early Tuesday.  Air mass modification will continue through
the day and into tonight ahead of the front, but the depth of
buoyancy and lightning potential are somewhat in question across FL
given the warm temperature profiles in the 800-650 mb layer, and the
stronger forcing for ascent passing well to the north of FL.

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