SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0700 AM CST Mon Feb 22 2021

Valid 221300Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST
VIRGINIA/EASTERN NORTH CAROLINA...

...SUMMARY...
A couple of strong to locally severe thunderstorms with gusty winds
may occur this afternoon across eastern North Carolina and/or
southeast Virginia.

...Synopsis...
A progressive upper trough and associated 150 kt 300 mb jet streak
will overspread the eastern CONUS through the day. Very strong
deep-layer wind fields are expected to precede the upper trough axis
and an approaching surface cold front during the afternoon hours
across portions of the Mid-Atlantic southward to Carolina coastal
areas. This is where a modified marine layer may promote very modest
low-level buoyancy, potentially supporting deep enough moist
convection to foster a few lightning flashes.

Farther south across southern Georgia into Florida, forcing for
ascent will be weaker as the upper trough is expected to remain
mainly north of the area. However, more appreciable instability will
be in place, with isolated thunderstorm development possible along a
weak but broad confluence zone ahead of a southward sagging cold
front.  

...Eastern North Carolina/southeast Virginia and vicinity...
Convective potential across the region is still not fully certain
given the initially cold/stable boundary layer across the region and
the influence of scattered showers upstream across the Appalachians
in vicinity of an eastward-moving cold front. However, early morning
RAP/HRRR runs appear to have trended a bit more conducive with
depictions of thermodynamic profiles potentially capable of a few
lightning strikes with low-topped convection this afternoon,
coincident with limited but non-zero surface-rooted buoyancy.
Furthermore, various convection-allowing models are plausibly
indicating the potential for an increasingly organized low-topped
convective line this afternoon centered across southeast Virginia
and eastern North Carolina (roughly 1-5 pm EST). Even if just
minimal near-surface-based buoyancy can become established
coincident with low/middle 50s F surface dewpoints, there seems to
be some potential for some convectively enhanced wind gusts given
the magnitude (50+ kt) of southwesterly winds within the lowest 3 km
AGL.

..Guyer.. 02/22/2021

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